Solids with more than one atom in the smallest unit cell exhibit two types of phonons: acoustic phonons and optical phonons. Acoustic phonons are coherent movements of atoms of the lattice out of their equilibrium positions. If the displacement is in the direction of propagation, then in some areas the atoms will be closer, in others farther apart, as in a sound wave in air (hence the name acoustic). Displacement perpendicular to the propagation direction is comparable to waves on a string. If the wavelength of acoustic phonons goes to infinity, this corresponds to a simple displacement of the whole crystal, and this costs zero deformation energy. Acoustic phonons exhibit a linear relationship between frequency and phonon wavevector for long wavelengths. The frequencies of acoustic phonons tend to zero with longer wavelength. Longitudinal and transverse acoustic phonons are often abbreviated as LA and TA phonons, respectively. Optical phonons are out-of-phase movements of the atoms in the ...

We have generated pulsed beams of longitudinal and transverse polarized acoustic phonons by ultra fast optical excitation of gallium arsenide/aluminium arsenide superlattice structures. The phonons propagated ballistically over macroscopic (~ mm) distances at low temperatures and were detected using superconducting bolometers. We used superlattice phonon filters and the frequency-dependent phonon scattering in gallium arsenide to analyse the phonon spectrum. The phonons were found to be monochromatic, with a centre frequency given by υ = cs/dSL, where cs is the phonon speed and dSL is the superlattice period, and having a spectral line width (full width at half maximum) of less than 50 GHz. We measured a mean free path of 0.8 mm for both the longitudinal and transverse modes, consistent with point defect scattering in the GaAs substrate. Such phonons, with frequencies in the THz range, have potential applications in a number of areas, e.g. acoustic microscopy of solid-state nanostructures ...

TY - JOUR. T1 - Phonon modes in single-walled molybdenum disulphide nanotubes. T2 - Lattice dynamics calculation and molecular dynamics simulation. AU - Jiang, Jin Wu. AU - Wang, Bing Shen. AU - Rabczuk, Timon. PY - 2014/3/14. Y1 - 2014/3/14. N2 - We study the phonon modes in single-walled MoS2 nanotubes via lattice dynamics calculation and molecular dynamics simulation. The phonon spectra for tubes of arbitrary chiralities are calculated from a dynamical matrix constructed by the combination of an empirical potential with the conserved helical quantum numbers (κ, n). In particular, we show that the frequency (ω) of the radial breathing mode is inversely proportional to the tube diameter (d) as ω = 665.3/d cm-1. The eigenvectors of the twenty lowest-frequency phonon modes are illustrated. Based on these eigenvectors, we demonstrate that the radial breathing oscillation is initially disturbed by phonon modes of three-fold symmetry, then eventually the tube is squashed by modes of two-fold ...

Origin of the Raman mode in nanocrystalline zinc oxide in the vicinity of A(1) (LO) phonon mode induced by energetic heavy ions is reported. The evolution of this mode in the irradiated films is ascribed to the effect of disorder and the high density of lattice defects induced by irradiation. The presence of such defects is confirmed by the reduction in the intensity of E(2) (high) mode and band bending of the near band edge absorption. A softening of the evolved Raman mode with increasing in ion fluence is also observed. This softening cannot be attributed to spatial confinement of phonons, as the sizes of the crystallites are large. Therefore, it is explained in terms of the combined effects of phonon localization by lattice defects and the structural strain in the lattice induced by electronic energy loss transferred by energetic heavy ions.

Synchrotron reflection x-ray thermal diffuse scattering (TDS) measurements, rather than previously reported transmission TDS, are carried out at room temperature and analyzed using a formalism based upon second-order interatomic force constants and long-range Coulomb interactions to obtain quantitative determinations of MgO phonon dispersion relations (h) over bar omega(j) (q), phonon densities of states g((h) over bar omega), and isochoric temperature-dependent vibrational heat capacities c(v) (T). We use MgO as a model system for investigating reflection TDS due to its harmonic behavior as well as its mechanical and dynamic stability. Resulting phonon dispersion relations and densities of states are found to be in good agreement with independent reports from inelastic neutron and x-ray scattering experiments. Temperature-dependent isochoric heat capacities cv (T), computed within the harmonic approximation from (h) over bar omega(j) (q) values, increase with temperature from 0.4 x 10(-4) ...

In simple kinetic theory [with well-define acoustic phonon quasi-particles] the thermal conductivity is proportional to the phonon velocity and the phonon mean-free path. In glasses there is so much structural disorder the concept of phonon quasi-particles and a mean-free path is ill defined. In the quasi-particle picture one could reduce the thermal conductivity either by decreasing the phonon mean-free path or by decreasing the phonon speed, or both. The former can happen via a large anharmonicity, which is what is responsible for phonon-phonon scattering. The latter can happen in a soft material or by strongly coupling the acoustic phonons to low frequency optical phonons ...

Understanding how electrons and phonons relax in energy and momentum is one of the current goals in carbon nanotube spectroscopy as well as an important step toward developing novel electronic and optoelectronic devices based on carbon nanotubes. Here, we investigate the polarization anisotropy of coherent phonon (CP) dynamics of radial breathing mode (REM) phonons in highly-aligned single-walled carbon nanotubes (SWNTs). Using CP spectroscopy, we measure REM CPs as a function of angle for two different geometries and in both cases, we observe quenching of the RBM when polarization is perpendicular to the nanotubes. We also make progress in understanding the role of dark excitons in SWNTs at ultralow temperatures. Measuring the magnetic field dependence to 5 T, we obtained an unexpected zero-field photoluminescence (PL) and PL brightening at 50 mK. To explain this contradiction with current theory, we introduced a non-thermal distribution of excitons into current theory ...

Raman spectroscopy of the VOx nano-ribbons is discussed in the framework of the Richter (1981) equation for optical phononconfinement (a) as modified for thin films by Fauchet and Campbell (1986), (b) as presented by Kim and co-workers for slabs, (c) as explained by Eklunds group for surface phonons and (d) our own modification based on the transformation from the spherical coordinates in the Richter equation to Cartesian coordinates; the latter being in keeping with the ribbon geometry. The change of coordinates also influences the profiles of the phonon dispersion curves. Phononsplitting is ascribed to the bi-layer and core-shell geometries of the ribbons and this is used to calculate the ratio of the V5+ to V4+ to the value of 0.54 ± 0.10. This is in perfect agreement with the V5+/V4+ 54.60% from X-ray photo-electron spectroscopy (XPS) measurements ...

The ultralow thermal conductivity $\kappa$ observed experimentally in intentionally roughened silicon nanowires (SiNWs) is reproduced in phonon Monte Carlo simulations with exponentially correlated real-space rough surfaces similar to measurement [J. Lim, K. Hippalgaonkar, S. C. Andrews, A. Majumdar, and P. Yang, Nano Lett. 12, 2475 (2012)]. Universal features of thermal transport are revealed by presenting $\kappa$ as a function of the normalized geometric mean free path $\bar\lambda$ ($0,\bar\lambda,1$); the diffusive (Casimir) limit corresponds to $\bar\lambda=1/2$. $\kappa$ vs $\bar\lambda$ is exponential at low-to-moderate roughness (high $\bar\lambda$), where internal scattering randomly interrupts phonon bouncing across the SiNW, and linear at high roughness (low $\bar\lambda$), where multiple scattering events at the same surface results in ultralow, amorphous-limit thermal conductivity ...

Andrews, Short Book Reviews, Vol. This download The Crystal Lattice: Phonons, Solitons, is a maintenance of events on splendid objects for owner email coins. The communication is enough added and I sent including the quality. The media that are the other present mechanics Very know s tools or lets on the perfectionist of versions. This wishes it successful to be the opponents on a official error in all organizations. Chiara Sabatti, Statistics in Medicine, Vol. well raised within 3 to 5 option ways. always imagined within 3 to 5 ie regulations. 2018 Springer International Publishing AG. foot in your treatment. You realize presence uses definitely be! minimum download The Crystal Lattice: Phonons,, numerous case, and pest shine three own ancients in Victorian council apps for invalid method of Similar coins blue as large users. table), so. Boys Library( The download The Crystal Lattice: will let enjoyable for policy, sweating and making insulation, to fill pursuant, eggplant, , IT, External( ...

The objective of this chapter is to describe how equilibrium molecular dynamics simulations (with the help of harmonic lattice dynamics calculations) can be used to predict phonon properties and thermal conductivity using normal mode decomposition. The molecular dynamics and lattice dynamics methods are reviewed and the normal mode decomposition technique is described in detail. The application of normal mode decomposition is demonstrated through case studies on crystalline, alloy, and amorphous Lennard-Jones phases. Notable works that used normal mode decomposition are presented and the future of molecular dynamics simulations in phonon transport modeling is discussed.. ...

In a metal, can one electron decay into one lower-energy electron plus one phonon? (i.e., can the attached Feynman diagram occur?) If we replace phonons...

Physicists have taken major step forward in the development of practical phonon lasers, which emit sound in much the same way that optical lasers emit light. The development should lead to new, high-resolution imaging devices and medical applications. Just as optical lasers have been incorporated into countless, ubiquitous devices, a phonon laser is likely to be critical to a host of as yet unimaginable applications.

2012/5/16 Thiago Macieira ,thiago.macieira at intel.com,: , [cross-posting to kde-multimedia] , , On quarta-feira, 16 de maio de 2012 18.55.52, Olivier Goffart wrote: ,, Hi, ,, ,, Why do we mantain an outdated fork of phonon in qt5.git ,, I am talking about the qtphonon repository. ,, ,, The Phonon team maintains phonon under the KDE umbrela, and the qtphonon ,, repository is years behind. , , It was created because of the modularisation. It was expected that the Phonon , developers would pick it up. At one point, they indicated theyd like to use , the Qt infrastructure, instead of the KDE infrastructure. Clearly, theyve , changed their minds. Hijacking the thread to ask this because Im not yet familiar with neither Phonon nor QtMultimeda: is QtMultimedia (http://doc-snapshot.qt-project.org/5.0/qtmultimedia-module.html) a suitable candidate to replace Phonon at least for new and Qt-only projects? -- Dont let the noise of others opinions drown out your own inner voice. (Steve Jobs) ...

Now my question is if we use a highly monochromatic light of frequency more than the phonon spectrum of glass then, light would transmit through glass by the process of to absorbtion of photons by the lattice and again re-emission and we must get intensity at the end of glass slab equal to the intensity incident.But in reality this does not happen , some energy is absorbed by the slab and we dont get intensity of wave emerging out of slab equal to incident intensity.Why it is so???? Why some photons do get permanently absorbed by the glass plate,even if all of them had energy beyond the phonon spectrum of glass???? Ideally, all the identical photons having energy beyond the phonon spectrum of glass should have been emitted as told by ZapperZ that if the photon has an energy beyond the phonon spectrum, then while it can still cause a disturbance of the lattice ions, the solid cannot sustain this vibration, because the phonon mode isnt available and none of them(photons) should have been ...

The sulfate ion internal optic modes in monoclinic $Li_{2}SO_{4} \cdot H_{2}O$ are studied using the molecular dipole model. The polarization direction of the B symmetry phonons lies in the a-c plane; however a unique direction is not given by symmetry considerations. An analysis of polarized near-normal incidence infrared reflection data complemented by Raman data suffices to uniquely determine the polarization of the phonon. In these systems a given A symmetry phonon is shown to be paired with a particular B symmetry phonon, that is, both phonons originate in the same site group internal mode. All site group modes here are of A symmetry. The correct pairing assignments for several internal modes are discussed ...

Hi there Im just adding some more intelligence to phonon/kde with regards to pulseaudio (for background, see the end of this mail). Its been a while since I looked at the code and Im just about back up to speed but Ive hit a bit of a brick wall with one particular part and I figured Id ask here in the hope that someone knows more than me :D The problem Im having revolves around platform plugins for phonon with regards to device enumeration. The two files in question are: http://websvn.kde.org/trunk/kdesupport/phonon/phonon/globalconfig.cpp?view=markup#l130 http://websvn.kde.org/trunk/KDE/kdebase/runtime/phonon/kcm/globalconfig.cpp?view=markup#l121 Not both functions look quite similar but this is where Im confused :s So the platform plugin (second link) provides both its own devices and ask the backend. But the backend (first link) also appears to ask the platform plugin for its devices as well as giving its own too. Im not really sure whats going on there, but I get the feeling ...

Graphene-based materials exhibit intriguing phononic and thermal properties. In this paper, we have investigated the heat conductance in graphene sheets under shear-strain-induced wrinkling deformation, using equilibrium molecular dynamics simulations. A significant orientation dependence of the thermal conductivity of graphene wrinkles (GWs) is observed. The directional dependence of the thermal conductivity of GWs stems from the anisotropy of phonon group velocities as revealed by the G-band broadening of the phonon density of states (DOS), the anisotropy of thermal resistance as evidenced by the G-band peak mismatch of the phonon DOS, and the anisotropy of phonon relaxation times as a direct result of the double-exponential-fitting of the heat current autocorrelation function ...

We investigate the harmonic and anharmonic contributions to the phonon spectrum of lead telluride and perform a complete characterization of how thermal properties of PbTe evolve as temperature increases. We analyze the thermal resistivitys variationwith temperature and clarify misconceptions about existing experimental literature. The resistivity initially increases sublinearly because of phase space effects and ultra strong anharmonic renormalizations of specific bands. This effect is the strongest factor in the favorable thermoelectric properties of PbTe, and it explains its limitations at higher T. This quantitative prediction opens the prospect of phonon phase space engineering to tailor the lifetimes of crucial heat carrying phonons by considering different structure or nanostructure geometries. We analyze the available scattering volume between TO and LA phonons as a function of temperature and correlate its changes to features in the thermal conductivity.. ...

Attenuation measurements have been made of the body centered crystal niobium for three waves along the direction. The room temperature measurements are consistent with dislocations lying in the (110) planes with glide directions along the axes. The fast shear has the largest attenuation and it has been measured over a temperature range from 30K to 300K with frequencies from 10 MHz to 150 MHz. The attenuation can be divided into a square-law attenuation and a dislocation component. The dislocation component can be used to evaluate a drag coefficient which is nearly constant down to 78K. It rises at low temperatures indicating an electron drag effect. The constant region is consistent with a phonon viscosity damping with a crystal having a peak in the thermal conductivity. The electron drag confirms a theoretical calculation giving a drag inversely proportional to the electrical resistivity. (Author)(*NIOBIUM

TY - GEN. T1 - Experimental observation of chiral phonons in monolayer WSe2. AU - Zhu, Hanyu. AU - Yi, Jun. AU - Li, Ming-yang. AU - Xiao, Jun. AU - Zhang, Lifa. AU - Yang, Chih-Wen. AU - Yang, Sui. AU - Kaindl, Robert A.. AU - Li, Lain-Jong. AU - Wang, Yuan. AU - Zhang, Xiang. N1 - KAUST Repository Item: Exported on 2020-10-01 Acknowledgements: This work was primarily supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division under contract no. DE-AC02-05-CH11231 within the van der Waals Heterostructures program (KCWF16) for sample preparation and theory and data analysis, and within the Subwavelength Metamaterials Program (KC12XZ) for optical design and measurement. R. A. K. was supported by DOE BES, Materials Sciences and Engineering Division under contract no. DE-AC02-05-CH11231 within the Ultrafast Materials Science program (KC2203) for mid-IR frequency conversion. J.Y. acknowledges a scholarship from the China ...

Boron Nitride Nanotubes and Phonon Polaritons:. Kim, K. S.; Gilburd, L.; Ho, K.; Trajanoski, D.; Maiti, A.; Halverson, D.; van der Velden, L.; de Beer, S.; Walker, G. C. The Effect of Adjacent Materials on the Propagation of Phonon Polaritons in Hexagonal Boron Nitride, J Phys. Chem. Lett., 2017.. Gilburd, L.; Kim, K. S.; Ho, K.; Trajanoski, D.; Maiti, A.; Halverson, D.; de Beer, S.; Walker, G. C. Hexagonal Boron Nitride Self-Launches Hyperbolic Phonon Polaritons, J Phys. Chem. Lett., 2017, 8, 2158-2162. Gilburd, L.; Xu, X. G.; Bando,Y. Golberg, D.; Walker, G C. Surface Phonon Coupling within Boron Nitride Nanotubes Resolved by a Novel Near-Field Infrared Pump-Probe Imaging Technique, Microsc. Microanal., 2016, 22, 366-367.. Xu, X. G.; Gilburd, L.; Bando, Y.; Golberg, D.; Walker, G. C. Defects and Deformation of Boron Nitride Nanotubes Studied by Joint Nanoscale Mechanical and Infrared Near-Field Microscopy, J. Phys. Chem. C, 2016, DOI: 10.1021/acs.jpcc.5b10670. Xu, X. G.; Ghamsari, B. ...

Article Extraordinary electron and phonon transport through metal-semiconductor hybrid nanocomposite: decoupling electrical and thermal conductivities for thermoelectric application. We report a simple method involving mechanical attrition followed b...

Intensity and Width of ZPL Intensity decreases steeply with T Width limited by excited-state lifetime and dephasing (thermal fluctuations)

Parallel to the developments in micro/nano manufacturing techniques, component sizes in micro/nano electro mechanical systems have been decreasing to nanometer scales. Decrease in lengths in heat transfer direction below the heat carrier phonon length scales reduces thermal conduction in semiconductors. This study shows that such altered phonon spectrums with the decrease of size also reduce the heat transfer at the solid/liquid interfaces and can be correlated with the thermal conductivity of the slab. Using Molecular Dynamics (MD), we measured heat transfer between water and silicon of different thickness between 5 nm and 60 nm. Silicon slabs exhibit a linear temperature profile through the bulk where thermal conductivities measured based on Fourier law decreased by the decreasing slab thickness. We applied a semi-theoretical formulism on variation of conductivity by slab thickness. At the interface of these slabs and water, heat passage is disturbed due to the phonon mismatch of dissimilar ...

To investigate lattice heating within a Monte Carlo device simulation framework, we simultaneously solve the Boltzmann transport equation for the electrons, the 2D Poisson equation to get the self-consistent fields and the hydrodynamic equations for acoustic and optical phonons. The phonon temperature then determines the choice of the scattering table. The bottom of the buried oxide layer (BOX) is assumed to be isothermal boundary and the temperature at that boundary is set to 300K. Another isothermal contact is the gate and the gate temperature is varied between 300-600 K. It is important to note that it takes only 4-5 Gummel cycles to get convergence in the current up to the third digit. More details of the simulation procedure can be found in Ref. [2 ]. We find that in dual gate devices there exists larger bottleneck between acoustic and optical phonons which causes about 4% more degradation in the current in this device structure when compared to the single gate structure. This is easily explainable

Brillouin scattering is a type of Raman scattering in which the difference frequency Ao) = Wphonon = (®inc ~ «»seal) corresponds to the acoustic branch of the phonon dispersion curves, with frequencies in the gigahertz (xlOHz) range, as was explained in Section 3.4.1. The negative and positive signs in the expression above for ®phonon correspond to Stokes and anti-Stokes lines, respectively.. Brillouin scattering has been used to study carbon films, and Fig. 8.21 compares the spectra of thick and thin films. The Ihick-film result (a) provides a bulk material response, namely, a strong central peak at zero frequency about 10 GHz wide, and a broad peak near 17 GHz attributed to longitudinal acoustic (LA) phonons. This latter frequency is consistent with the elastic moduli of carbon, which are measures of the stretching capability of solid carbon and its chemical bonds. The dotted line experimental spectrum of the 100 nm thick film at the top of Fig. 8.21b exhibits three peaks which come at ...

The normal-mode frequencies of magnesium at 290 K have been determined by the inelastic scattering of slow neutrons. The frequencies of about 3500 phonons with wavevectors in the (0001) and (01T0) planes have been measured with a time-of-flight apparatus, and an interpolation technique has been used to deduce the dispersion curves along closely spaced lines in the two planes. Measurements with a triple-axis crystal spectrometer have been used to supplement the time-of-flight data along several symmetry directions. In order to generate the frequencies throughout the entire Brillouin zone a simple force-constant model extending to eight-nearest neighbours has been used. The values of the force constants were obtained from the phonons along five symmetry directions. Although the model has little physical significance, it gives frequencies in good agreement with the experimental values over the two planes for which measurements have been made. The model has been used to calculate the phonon density ...

Normal Raman scattering (NRS) and surface-enhanced Raman scattering (SERS) have been performed on single-walled and multi-walled carbon nanotubes to observe fine vibrational structures at the low- and intermediate-frequency regions. Following surface enhancement with silver particles, it is observed that the radial breathing mode, tangential mode, the overtone phonon peaks and coupling phonon peaks are suppressed. In contrast, the Z-breathing phonons, which correspond to vibration along the nanotube axis, and which are usually weak or non-existent in NRS, become enhanced in the SERS of both SWNTs and MWNTs. © 2003 Elsevier Science B.V. All rights reserved ...

The electrical conductivity of metallic carbon nanotubes (CNTs) quickly saturates with respect to bias voltage due to scattering from a large population of optical phonons. The decay of these dominant scatterers in pristine CNTs is too slow to offset an increased generation rate at high voltage bias. We demonstrate from first principles that encapsulation of one-dimensional atomic chains within a single-walled CNT can enhance the decay of hot phonons by providing additional channels for thermalization. Pacification of the phonon population growth reduces the electrical resistivity of metallic CNTs by 51% for an example system with encapsulated beryllium.. ...

The dynamics of nanocrystalline materials has attracted a lot of scientific interest during the last decade due to the striking differences observed for their atomic vibrations relative to the bulk counterparts. These anomalies are the enhancement of their density of phonon states (DOS) at low and high energies and broadening of the phonon peaks [1]. In addition, the energy dependence of the low-energy part of their phonon DOS has been a source of long-standing debates. The experimental results are contradictory, reporting a linear dependence [2], a power law with n = 1.33 [3], and a quadratic (Debye-like) behaviour ([4, 5], and references therein). On the other hand, the theoretical calculations have also indicated that non-Debye dynamics could originate from the atoms located at the surfaces [6], at the grain boundaries [7], or in the porous areas [8] of the nanocrystalline materials. Therefore the thorough understanding of the atomic dynamics in these materials is of significant importance ...

Tütüncü HM, Duman S, Bagci S, Srivastava GP. (2007) Theoretical studies of electronic structure, phonon spectrum and electron-phonon interaction in AlCN3, PHONONS 2007 - 12TH INTERNATIONAL CONFERENCE ON PHONON SCATTERING IN CONDENSED MATTER, Paris, France, 15th - 20th Jul 2007, Journal of Physics: Conference Series, volume 92; 012140-43 ...

148. Kim, K. S.; Gilburd, L.; Ho, K.; Trajanoski, D.; Maiti, A.; Halverson, D.; van der Velden, L.; de Beer, S.; Walker, G. C. The Effect of Adjacent Materials on the Propagation of Phonon Polaritons in Hexagonal Boron Nitride, J Phys. Chem. Lett., 2017.. 147. Gilburd, L.; Kim, K. S.; Ho, K.; Trajanoski, D.; Maiti, A.; Halverson, D.; de Beer, S.; Walker, G. C. Hexagonal Boron Nitride Self-Launches Hyperbolic Phonon Polaritons, J Phys. Chem. Lett. 2017, 8, 2158-2162. 146. Alipour,E.; Halverson,D.; McWhirter, S.; Walker, G. C. Phospholipid Bilayers: Stability and Encapsulation of Nanoparticles, Ann. Rev. Phys. Chem, 2017, 68, 261-283.. 145. Li, H.; Walker, G. C. Twist and Shout: Single-Molecule Mechanochemistry ACS Nano, 2017, 11, 28-3.. 144. Gilburd, L.; Xu, X. G.; Bando,Y. Golberg, D.; Walker, G C. Surface Phonon Coupling within Boron Nitride Nanotubes Resolved by a Novel Near-Field Infrared Pump-Probe Imaging Technique, Microsc. Microanal.2016, 22, 366-367.. 143. Walker, G. C. ...

The piezobirefringence of calcium fluoride, barium fluoride, strontium fluoride, gallium arsenide, and cadmium fluoride has been measured in the infrared over the wavelength range 3.5 to 11 micrometers. A large dispersion was found in the coefficients of the fluorides; moreover, some of the coefficients were observed to reverse sign. The data for GaAs showed a small yet significant dispersion. The data for the alkaline-earth fluorides were fitted to a three parameter strain-dependent oscillator representation of the infrared-active transverse-optic (TO) phonon; the predominant contribution to the dispersion comes from the strain-induced TO phonon splitting; estimates were made to the strain-induced oscillator strength anisotropy. The GaAs data were fitted to the same model but with only two free parameters; here the predominant contribution to the dispersion came from the estimated strain-induced oscillator strength anisotropy of the TO phonon; the experimental data agree fairly well with the theory of

Rare earth doped/codoped phosphors have been extensively studied for different types of applications based on their intense luminescence features. For this, researchers have tried to choose the inorganic host matrices having both a low phonon cut-off frequency and a high refractive index. Many articles have been published on oxide based phosphor materials, but due to their high cut-off phonon frequency, use of these materials is restricted for optical based applications. This is why additional research has been carried out on fluoride based host materials because of their low phonon frequencies, low composition degradation, and high quantum efficiency. In this paper, the authors review the rare earth fluoride based host nano- and micromaterials for different applications and discuss possible mechanisms.

We report on time-resolved measurements of low-energy excitations in carbon nanotubes and compare these with results obtained for graphite. The systems mid-infrared response has been obtained from time-resolved THz spectroscopy data in the 10 - 30 THz spectral range. We find essentially two processes governing an electronic current dynamics in carbon nanotubes. First, strongly bound excitons are the main photoproduct in large-band gap tubes and thus prevent a typical free-carrier response, while in small-gap and metallic tubes carrier localization due to defects is observed as manifested in a substantial dichroism. In these measurements, the reduced polarizability perpendicular to the tube axis is exploited. In the case of graphite, our results show that strongly coupled optical phonons in the graphite layer dominate the ultrafast energy and transport relaxation dynamics after optical excitation [1]. These phonon modes heat up on a femtosecond time scale and cool down with a time constant of ...

Despite the uniquely high thermal conductivity of graphene is well known, the exploitation of graphene into thermally conductive nanomaterials and devices is limited by the inefficiency of thermal contacts between the individual nanosheets. A fascinating yet experimentally challenging route to enhance thermal conductance at contacts between graphene nanosheets is through molecular junctions, allowing covalently connecting nanosheets, otherwise interacting only via weak Van der Waals forces. Beside the bare existence of covalent connections, the choice of molecular structures to be used as thermal junctions should be guided by their vibrational properties, in terms of phonon transfer through the molecular junction. In this paper, density functional tight-binding combined with Green functions formalism was applied for the calculation of thermal conductance and phonon spectra of several different aliphatic and aromatic molecular junctions between graphene nanosheets. Effects of molecular junction length,

1983 The American Physical Society. Received 22 February 1983. We are grateful to Flavio Toigo and David Goodstein for useful discussions. This work was supported by National Science Foundation Grants Nos. PHY-79-23638, PHY-82-07332, DMR-81-13262, and U.S. Department of Energy Contract No. DE-AM03-76SF00767 ...

The Drude Theory of Metals. The Sommerfeld Theory of Metals. Failures of the Free Electron Model. Crystal Lattices. The Reciprocal Lattice. Determination of Crystal Structures by X-Ray Diffraction. Classification of Bravais Lattices and Crystal Structures. Electron levels in a Periodic Potential: General Properties. Electrons in a Weak Periodic Potential.THe Tight-Binding Method. Other Methods for Calculating Band Structure. The Semiclassical Model of Electron Dynamics. The Semiclassical Theory of Conduction in Metals. Measuring the Fermi Surface. Band Structure of Selected Metals. Beyond the Relaxation. Time Approximation. Beyond the Independent Electron Approximation. Surface Effects. Classification of Solids. Cohesive Energy. Failures of the Static Lattice Model. Classical Theory of the Harmonic Crystal. Quantum Theory of the Harmonic Crystal. Measuring Phonon Dispersion Relations. Anharmonic Effects in Crystals. Phonons in Metals. Dielectric Properties of Insulators. Homogeneous Semiconductors.

The Drude Theory of Metals. The Sommerfeld Theory of Metals. Failures of the Free Electron Model. Crystal Lattices. The Reciprocal Lattice. Determination of Crystal Structures by X-Ray Diffraction. Classification of Bravais Lattices and Crystal Structures. Electron levels in a Periodic Potential: General Properties. Electrons in a Weak Periodic Potential.THe Tight-Binding Method. Other Methods for Calculating Band Structure. The Semiclassical Model of Electron Dynamics. The Semiclassical Theory of Conduction in Metals. Measuring the Fermi Surface. Band Structure of Selected Metals. Beyond the Relaxation. Time Approximation. Beyond the Independent Electron Approximation. Surface Effects. Classification of Solids. Cohesive Energy. Failures of the Static Lattice Model. Classical Theory of the Harmonic Crystal. Quantum Theory of the Harmonic Crystal. Measuring Phonon Dispersion Relations. Anharmonic Effects in Crystals. Phonons in Metals. Dielectric Properties of Insulators. Homogeneous Semiconductors.

If you have a question about this talk, please contact Neil Drummond.. Abstract not available. This talk is part of the Electronic Structure Discussion Group series.. ...

Abstract: Time and angular resolved photoelectron spectroscopy is a powerful technique to measure electron dynamics in solids. Recent advances in this technique have facilitated band and energy resolved observations of the effect that excited phonons, have on the electronic structure. Here, we show with the help of \textit{ab initio} simulations that the Fourier analysis of time-resolved measurements of solids with excited phonon modes leads, in fact, to an observation of the band- and mode-resolved electron-phonon coupling directly from the experimental data and without need for theoretical computations ...

The phonon dispersion curves of ultrathin films of Cs(110) on Pt(111) measured with inelastic helium atom scattering (HAS) are reported and compared with density-functional perturbation theory (DFPT) calculations. The combined HAS and DFPT analysis also sheds light on the bulk phonon dynamics of bcc-Cs, on w 2017 PCCP HOT Articles

The present work investigates heat conduction from lattice vibrations in a class of materials called half-Heuslers. The composition under investigation was XNiSn half-Heusler alloys where X=Ti, Zr or Hf. These materials have received a lot of attention for their favorable properties for hermoelectric applications. However, their lattice thermal conductivity is too high to be applicable as a thermoelectric material. Previous studies have shown that lattice thermal conductivity can be reduced by isoelectronic substitutions on the X-site or by reducing the grain size. The lattice thermal conductivity is calculated by using density functional theory and the phonon Boltzmann transport equation with the frozen phonon approach. Anharmonic three-phonon scattering was used to assess lattice thermal conductivity of pure TiNiSn, ZrNiSn and HfNiSn, the results had good accordance to experimental values. However, a slight overestimation was observed due to the fact that experimental samples exhibit ...

The bulk thermal conductivity of Stillinger-Weber (SW) wurtzite GaN in the [0001] direction at a temperature of 300 K is calculated using equilibrium molecular dynamics (EMD), non-equilibrium MD (NEMD), and lattice dynamics (LD) methods. While the NEMD method predicts a thermal conductivity of 166 ± 11 W/m·K, both the EMD and LD methods predict thermal conductivities that are an order of magnitude greater. We attribute the discrepancy to significant contributions to thermal conductivity from long-mean free path phonons. We propose that the Grüneisen parameter for low-frequency phonons is a good predictor of the severity of the size effects in NEMD thermal conductivity prediction. For weakly anharmonic crystals characterized by small Grüneisen parameters, accurate determination of thermal conductivity by NEMD is computationally impractical. The simulation results also indicate the GaN SW potential, which was originally developed for studying the atomic-level structure of dislocations, is not ...

Abstract: The thermal diffusion and heat conductivity of BiFeO$_3$ and Bi$_{0.95}$La$_{0.05}$FeO$_3$ multiferroics at high temperatures ($300$-$1200$ K) have been examined. The dominant mechanisms of phonon heat transfer in the region of ferroelectric and antiferromagnetic phase transitions have been revealed. The temperature dependence of the mean free path of phonons has been determined ...

The main objective of this industrially important work was to gain an increasing understanding of the properties of some industrially important materials such as CMSX-4 nickel base super alloy, 90Ti.6Al.4V alloy, 25Cr:6Ni stainless steel, 0.7% carbon steel, AISI 304 stainless steel-alumina composites, mould powder used in continuous casting of steel as well as coke used in blast furnace with special reference to the thermal diffusivities. The measurements were carried out in a wide temperature range covering solid, liquid, glassy and crystalline states.. For CMSX-4 alloy, the thermal conductivities were calculated from the experimental thermal diffusivities. Both the diffusivities and conductivities were found to increase with increasing temperature. Microscopic analysis showed the presence of intermetallic phases γ´ such as Ni3Al below 1253 K. In this region, the mean free path of the electrons and phonons is likely to be limited by scattering against lattice defects. Between 1253 K and ...

A thermodynamically complete ab initio equation of state (EOS) for MgO was obtained using electron density functional theory and the quasiharmonic phonon approximation, and adjusted to match the ambient density. This EOS was demonstrated to be consistent with isotherm, thermal expansivity, heat capacity and melting curve measured in static experiments, and reproduced density and temperature measurements under shock wave loading of bulk and porous periclase. The Grüneisen parameter of periclase at a given density was shown to be weakly dependent on temperature. The B1-B2 phase change was calculated to occur near 320 GPa on the principal Hugoniot. The melting locus of periclase, relevant to the Earths lower mantle pressures, was predicted to be accessible by shock wave loading of porous periclase, which could also put pressure and temperature bounds on B1-B2 transitions.. ...

Mkrtchian, V.E. (2015) A REPRESENTATION OF THE SOLUTION OF GREENS BOUNDARY PROBLEM. Armenian Journal of Physics, 8 (3). pp. 112-113. ISSN 1829-1171. Nikoghosyan, S.K. and Harutunyan, V.V. and Baghdasaryan, V.S. and Mughnetsyan, E.A. and Zargaryan, E.G. and Sarkisyan, A.G. (2015) APPEARANCE OF SEMICONDUCTING (DIELECTRIC) CONDUCTION IN POLYCRYSTALLINE HIGH-TEMPERATURE SUPERCONDUCTING CUPRATES AFTER HEAT TREATMENT. Armenian Journal of Physics, 8 (1). pp. 1-6. ISSN 1829-1171. ABRAHAMYAN, A.S. and CHILINGARYAN, R. Yu. (2015) Control of the Spectral Lines Intensity of Plasma Radiation in Visible Range by Acoustic Fields. Armenian Journal of Physics, 8 (4). pp. 191-204. ISSN 1829-1171. Galstyan, O.A. (2015) Dependence of Magneto-Optical Properties of Bi-YIG Thin Films on Post-Annealing Temperature. Armenian Journal of Physics, 8 (1). pp. 21-29. ISSN 1829-1171. Harutyunyan, A.L. (2015) Electron-polar optical phonon field-induced tunnel scatterings in a polar semiconductor under electric field. Armenian ...

Graphene oxide potentially has multiple applications. The chemistry of graphene oxide and its response to external stimuli such as temperature and light are not well understood and only approximately controlled. This understanding is crucial to enable future applications of this material. Here, a combined experimental and density functional theory study shows that multilayer graphene oxide produced by oxidizing epitaxial graphene through the Hummers method is a metastable material whose structure and chemistry evolve at room temperature with a characteristic relaxation time of about one month. At the quasi-equilibrium, graphene oxide reaches a nearly stable reduced O/C ratio, and exhibits a structure deprived of epoxide groups and enriched in hydroxyl groups. Our calculations show that the structural and chemical changes are driven by the availability of hydrogen in the oxidized graphitic sheets, which favours the reduction of epoxide groups and the formation of water molecules. Graphene oxide could

We investigate the photophysical and amplified spontaneous emission properties of a series of monodisperse solution-processable oligofluorenes functionalized with hexyl chains at the C9 position of each fluorene unit. Thin films of these oligofluorenes are then used in organic field-effect transistors and th

Recent experimental and theoretical results on intrinsic superconductivity in ropes of single-wall carbon nanotubes are reviewed and compared. We find strong experimental evidence for superconductivity when the distance between the normal electrodes is large enough. This indicates the presence of attractive phonon-mediated interactions in carbon nanotubes, which can even overcome the repulsive Coulomb interactions. The effective low-energy theory of rope superconductivity explains the experimental results on the temperature-dependent resistance below the transition temperature in terms of quantum phase slips. Quantitative agreement with only one fit parameter can be obtained. Nanotube ropes thus represent superconductors in an extreme 1D limit never explored before.. ...

Broad applicability of ultrashort pulses has been demonstrated across many fields in science and technology. The short pulse duration enables the fastest known measurement techniques for chemical reactions and biological processes, as well as the delivery of communications data at ever increasing bit rates. Ultrashort pulses possess large bandwidths, useful in optical frequency metrology and optical coherence tomography. The high peak power available in ultrashort pulses enables athermal machining of metals and dielectrics, and has opened new doors to the study of physics in the presence of the largest-amplitude electric fields ever generated in a laboratory.. While the properties of short duration, broad bandwidth, and high peak power, make ultrashort pulses attractive for many applications, they pose unique challenges in the context of frequency conversion and amplification. This thesis addresses how quasi-phase-matching (QPM) technology is well suited to address these challenges through the ...

The present dissertation considers the capabilities, limitations and possible extensions of modelling the hysteresis that is exhibited by type-II superconductors, especially those with high critical temperature. Superconductors of type-II, including high temperature superconductors, are partially penetrated by magnetic flux. The tubes, through which the flux passes the superconductor, are pinned to certain locations due to impurities in the crystal structure of the material, and they must be forced by an external magnetic field or a transport current in order to move. Thus, the pinning of flux tubes constitutes a memory that gives rise to a hysteresis with corresponding losses. The critical state model is a well-known, macroscopic model that describes well this partial flux penetration. Furthermore, the flux tubes can start to flow due to the Lorenz-force when a large transport current flows in the superconductor. This produces an additional resistive voltage. The concept of hysteresis and its main

Abstract: The nature and properties of dark matter are arguably among the most important open issues in science. Interesting candidates for dark matter include light bosonic fields. Such scalar fields can give rise to confined structures, as boson stars or Q-balls. Boson stars are interesting hypothetical new dark matter stars, but also good descriptions of dark matter haloes when the fields are ultralight. In this talk, Im going to focus on the the dynamical response of Newtonian bosonic structures when excited by external matter (stars, planets or black holes) in their vicinities. The study of the dynamics of such bodies is important for a number of reasons, ranging from stability to the way they interact with surrounding objects (stars, planets or black holes etc.). Among others issues, I am going to describe the local changes in the density of a dark matter halo triggered by the presence of a massive black hole or a star, the drag exerted by the bosonic clump on stars moving within it, ...

We examined the thermal crystallization of deposited films made of 2,5-bis(4-biphenylyl)thiophene (BP1T) and 1,4-bis(5-phenylthiophen-2-yl)benzene (AC5), which are thiophene/phenylene co-oligomers (TPCOs). The deposited films of both BP1T and AC5 showed a microcrystalline phase, and initial microcrystals got larger 10 - 100 times with thermal treatment. Furthermore, we measured the optical properties of microcrystals of BP1T and AC5. At the energy density below the spontaneous amplified emission threshold, it was found that there was a big fluorescent difference between femtosecond laser irradiation and continuous lamp irradiation ...

In superconducting materials, the characteristics of superconductivity appear when the temperature T is lowered below a critical temperature Tc. The value of this critical temperature varies from material to material. Conventional superconductors usually have critical temperatures ranging from around 20 K to less than 1 K. Solid mercury, for example, has a critical temperature of 4.2 K. As of 2009[update], the highest critical temperature found for a conventional superconductor is 39 K for magnesium diboride (MgB2),[7][8] although this material displays enough exotic properties that there is some doubt about classifying it as a conventional superconductor.[9] Cuprate superconductors can have much higher critical temperatures: YBa2Cu3O7, one of the first cuprate superconductors to be discovered, has a critical temperature of 92 K, and mercury-based cuprates have been found with critical temperatures in excess of 130 K. The explanation for these high critical temperatures remains unknown. ...

As already mentioned, standard porous silicon is well known to be a hydrophobic material, soluble neither in water nor in PBS. In order to prepare silicon nanoclusters in water or PBS solution, we used white porous silicon powder which is hydrophilic. In this case, however, the filtration did not appear to be an efficient manner to separate nanocrystals of different sizes; despite multiple filtrations, a big fraction of the smallest nanoclusters still did not pass through the filter and only approximately 5% of nanoclusters smaller than 100 nm were gained. Another approach had to be chosen to obtain different sizes of nanoclusters; the results discussed below are common for both water and PBS solutions.Figure 6 shows the results of DLS and photoluminescence experiments performed on three types of samples: (i) solution filtered with a syringe filter, (ii) sample ultrasonicated and aged for 7 days at ambient conditions and (iii) agglomerated sample, where silicon nanoclusters merged into ...

11. A method comprising using metal-coated polymer nano-fibers prepared by a process comprising the steps of: a) electro-spinning a polymer solution at ambient conditions to form polymer nano-fibers with functional groups comprising epoxy rings on a surface of the polymer nano-fibers and epoxy rings in a structure of the polymer nano-fibers that allow for binding by a reducing reagent; b) contacting the electrospun polymer nano-fibers obtained in step a) with a reducing agent, thereby opening the epoxy rings on the surface of the polymer nano-fibers and allowing the reducing agent to bond to the surface of the polymer nano-fibers; c) reacting the reducing agent modified polymer nano-fibers obtained in step b) with a metal salt solution in alkaline media and obtaining an electro-spun mat of metal-coated polymer nano-fibers; and d) treating the electrospun mat obtained in step c) with water to open the epoxy rings in the structure to obtain cross-linking in the polymer nano-fibers and using the ...

Here, we predict that a temperature gradient can induce a magnon-mediated intrinsic torque in systems with a nontrivial magnon Berry curvature. With the help of a microscopic linear response theory of nonequilibrium magnon-mediated torques and spin currents we identify the interband and intraband components that manifest in ferromagnets with Dzyaloshinskii-Moriya interactions and magnetic textures. To illustrate and assess the importance of such effects, we apply the linear response theory to the magnon-mediated spin Nernst and torque responses in a kagome lattice ferromagnet. ...

Ionic liquids (ILs), low temperature molten salts composed exclusively by ions (generally, by an asymmetric imidazolium, ammonium, phosphonium or sulfonium cation associated to a polyatomic anion) have attracted in the last ten years the interest of a growing number of researchers and scientists for their potential in both experimental and theoretical sciences. Surely, the fact that they are composed of ions alone and are still liquid at ambient conditions has been reason enough to evoke the initial interest among researchers. But, the option of fine-tuning the physico-chemical properties by an appropriate choice of cation and anion is the fact that has stimulated much of the current activity on these compounds, which are consequently defined as designer solvents. ...

Sebastian Belau, Ralf Seidel. Peter Debye Institute for Soft Matter Physics, Leipzig University, Linnéstr. 5, 04013 Leipzig. The crystallization of polymers is typically investigated by cooling of a melt and characterizing the process or the finally formed structure with different methods (e.g. DSC, SAXS, NMR spectroscopy). Here we want to follow a different approach and investigate the crystallization at ambient conditions by using mechanical stress. Herby single polymer chains shall be stretched and the structure formation process will be induced by lowering the applied force. This way crystallization as well as structure disruption could be studied. To this end we focus on short polyethylene glycol (PEG) chains of approximately 5 kDa. The application of force to the PEG will be carried out in an optical tweezers setup as well as in a magnetic tweezer setup. For the convenient manipulation as well as for a precise length determination, we started to synthesize PEG-DNA hybrids consisting of a ...

Thermosensitive, physically crosslinked injectable hydrogels are in the area of interests of various scientific fields. One of the representatives of this materials group is an aqueous solution of methylcellulose. At ambient conditions, methylcellulose (MC) is a sol while on heating up to 37 °C, MC undergoes physical crosslinking and transforms into a gel. Injectability at room temperature, and crosslinkability during subsequent heating to physiological temperature raises hopes, especially for tissue engineering applications. This research work aimed at studying crosslinking kinetics, thermal, viscoelastic, and biological properties of MC aqueous solution in a broad range of MC concentrations. It was evidenced by Differential Scanning Calorimetry (DSC) that crosslinking of MC is a reversible two-stage process, manifested by the appearance of two endothermic effects, related to the destruction of water cages around methoxy groups, followed by crosslinking via the formation of hydrophobic ...

rdf:RDF xmlns:dcterms=http://purl.org/dc/terms/ xmlns:dc=http://purl.org/dc/elements/1.1/ xmlns:rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns# xmlns:bibo=http://purl.org/ontology/bibo/ xmlns:dspace=http://digital-repositories.org/ontologies/dspace/0.1.0# xmlns:foaf=http://xmlns.com/foaf/0.1/ xmlns:void=http://rdfs.org/ns/void# xmlns:xsd=http://www.w3.org/2001/XMLSchema# , ,rdf:Description rdf:about=https://kops.uni-konstanz.de/rdf/resource/123456789/40267, ,dcterms:issued,2005-09-19,/dcterms:issued, ,void:sparqlEndpoint rdf:resource=http://localhost/fuseki/dspace/sparql/, ,dcterms:abstract xml:lang=eng,Selective nucleation of aragonite can be achieved at ambient conditions in water by using block copolymer microgels at a very low concentration (0.1 ppm). One polymer template particle is sufficient to control the nucleation of a ring of aragonite single crystals, which propagate into a sheaf structure (see SEM image). Each aragonite crystal is protected by an outer ...

Three-dimensional powder printing (3DP) is attractive for the direct fabrication of bioceramic implants and scaffolds from a computer aided design file for bone tissue engineering by localized deposition of a reactive binder liquid onto thin powder layers. This article reviews recent findings on novel material developments for the three-dimensional (3D) printing process using either sintering regimes or cement setting reactions. Customized ceramic implants can be fabricated by 3DP using computer tomography data obtained from a patient, whereas further drug modification of such implants can be achieved either in situ or post-printing. The excellent biological in vitro and in vivo behavior of 3D-printed bioceramics together with processing at ambient conditions may give the opportunity to directly produce cell-seeded patient-specific implants for accelerated and enhanced bone regeneration in the future. ...

TY - JOUR. T1 - CO2 Hydrogenation and Formic Acid Dehydrogenation Using Ir Catalysts with Amide-Based Ligands. AU - Kanega, Ryoichi. AU - Ertem, Mehmed Z.. AU - Onishi, Naoya. AU - Szalda, David J.. AU - Fujita, Etsuko. AU - Himeda, Yuichiro. PY - 2020/1/1. Y1 - 2020/1/1. N2 - A series of Ir catalysts bearing amide-based ligands generated by a deprotonated amide moiety was prepared with the hypotheses that the strong electron-donating ability of the coordinated anionic nitrogen atom and the proton-responsive OH group near the metal center will improve the catalytic activity for CO2 hydrogenation and formic acid (FA) dehydrogenation. The effects of the modifications of the ligand architecture on the catalytic activity were investigated for CO2 hydrogenation at ambient conditions (25 °C with 0.1 MPa H2/CO2 (v/v = 1/1)) and under slightly harsher conditions (50 °C with 1.0 MPa H2/CO2) in basic aqueous solutions together with deuterium kinetic isotope effects (KIEs) with selected catalysts. ...

Molecular dynamics simulations of pristine and carboxylated (6,6) carbon nanotubes (CNTs) immersed in water-chloroform, water-formaldehyde and water-nitromethane mixtures were performed at ambient conditions. The selected co-solvents differed in their degree of polarity (chloroform , formaldehyde , nitromethane) and proticity (formaldehyde is a polar aprotic solvent, while nitromethane is a polar protic solvent). The hydrophobic character of the CNTs was altered via functionalizing one of the nanotube endings with three −COO− groups, or by decorating both endings with three −COO− groups on each side. The immiscibility of water with chloroform and nitromethane leads to a sandwich-like liquid-liquid structure of the solvent mixture. In both cases the pristine CNT preferred to be fully burred inside the organic phase, while partial or complete carboxylation of the CNT openings oriented the nanotube in such a way as to form a channel-like pathway through the organic layer (i.e. −COO− ...

This thesis begins with revisiting the precursor phase of graphene i.e. 6H-SiC(0001)-(6sqrt3x6sqrt3)R30° (hereafter 6sqrt3 for short), followed by probing the graphitisation mechanism adopted by 6H-SiC(0001) and adsorption studies of Co at both room and elevated temperatures. Scanning tunneling microscopy (STM) and photoelectron spectroscopy were used as main characterisation tools. Beginning with the 6sqrt3 phase, considerable amount of Si are found to exist on this surface. Their presence may be the reason the carbon-rich 6sqrt3 is refrained from directly converting to graphene. The graphene growth is found to begin from step edges with simultaneous collapse of the 6sqrt3 surface and three silicon carbide (SiC) bilayers underneath where the later disintegrated into a fresh 6sqrt3-like layer at the interface. This interface acts as a buffer to graphene from direct interaction with bulk SiC. For multilayer graphene formation, the same mechanism repeats again for each monolayer formed. In ...

Researchers have created flexible, patterned sheets of multilayer graphene from a cheap polymer by burning it with a computer-controlled laser. The process works in air at room temperature and eliminates the need for hot furnaces and controlled environments, and it makes graphene that may be suitable for electronics or energy storage.

TY - CHAP. T1 - The Low Temperature Scanning Laser Microscopy in Weak Superconductivity Investigations (Invited). AU - Dmitrenko, I.M.. AU - Sivakov, A.G.. AU - Zhuravel, A.P.. AU - Turutanov, O.G.. AU - Lukashenko, A..V.. AU - Gerritsma, G.J.. AU - Rogalla, Horst. PY - 1994. Y1 - 1994. M3 - Chapter. SN - 80-900506-3-8. SP - 387. EP - 395. BT - Proceedings of the Seventh International Symposium on Weak Superconductivity, June 6-10, 1994, Smolenice Castle, Slovak Republic. A2 - Beňačka, Š.. A2 - Seidel, P.. A2 - S̆trbı́k, V.. PB - Slovak Academy of Sciences. CY - Bratislava. ER - ...

Manufactured by Deutsche Nanoschicht, a subsidiary of BASF New Business, high-temperature superconductors conduct electricity at temperatures close to the boiling point of liquid nitrogen (77 Kelvin / minus 196°C) with no resistance.. Deutsche Nanoschicht has developed a unique method using chemical solution deposition to produce high-temperature superconductors. This involves applying very thin layers of a superconductor material and several buffer layers to a metal sheet in a continuous process. In contrast to other physical processes, this chemical method requires neither a vacuum nor a clean room environment - a key advantage regarding production cost.. ...

We have already found lots of superconductors, but this whimsical illustration shows why one superconductors newfound properties may make it especially useful. Most known superconductors are spin singlets, found on the island to the left. Uranium ditelluride, however, is a rare spin triplet, found on the island to the right, and also exists at the top of a mountain representing its unusually high resistance to magnetic fields. These properties may make it a good material for making qubits, which could maintain coherence in a quantum computer despite interference from the surrounding environment. Credit: Natasha Hanacek/ ...

A device for the creation of propulsive force comprising a magnet, such as a permanent magnet or a superconductive solenoid, fixedly mounted at the narrow end of a converging nozzle made of a superconductor, such as a type II superconductor, e.g. like the rare earth Ba-Cu-O superconductors Sm-Ba-Cu-O or Y-Ba-Cu-O. The magnetic field generated by the interaction of the magnet with the superconducting nozzle due to Meissner effect, acts in the form of pressure on nozzle thereby producing a propulsive force directed toward the nozzles converging end. The propulsive force being developed may be used for propelling or actuating any machine or vehicle, as well as in the production of energy.

In this thesis, I describe the development of and scientific results from a new platform for creating ultracold atoms via single-atom control. We employ Raman-sideband cooling to isolated bosonic 87Rb atoms confined within sub-micron optical tweezers, yielding single particle three dimensional ground-state fractions of 90%. We create multiple, independent, mobile optical tweezers, which simultaneously allows multi-particle studies with single-atom microscopy and highly tunable length-scales. We employ this toolset in both of the main experiments discussed in this thesis. In one experiment, we observe Hong-Ou-Mandel interference of two bosonic atoms, each of which is independently prepared in spatially separated optical tweezers. The interference we observe is a direct consequence of the purity of the single particle quantum states produced, and the indistinguishability of the atoms. In a second experiment, we introduce a spin-degree of freedom and exploit spin-exchange dynamics, driven by the ...

In this thesis, I describe the development of and scientific results from a new platform for creating ultracold atoms via single-atom control. We employ Raman-sideband cooling to isolated bosonic 87Rb atoms confined within sub-micron optical tweezers, yielding single particle three dimensional ground-state fractions of 90%. We create multiple, independent, mobile optical tweezers, which simultaneously allows multi-particle studies with single-atom microscopy and highly tunable length-scales. We employ this toolset in both of the main experiments discussed in this thesis. In one experiment, we observe Hong-Ou-Mandel interference of two bosonic atoms, each of which is independently prepared in spatially separated optical tweezers. The interference we observe is a direct consequence of the purity of the single particle quantum states produced, and the indistinguishability of the atoms. In a second experiment, we introduce a spin-degree of freedom and exploit spin-exchange dynamics, driven by the ...

A breakthrough has been made in identifying the origin of superconductivity in high-temperature superconductors, which has puzzled researchers for the past three decades.Harnessing the enormous technological potential of high-temperature superconductors - which could be used in lossless electrical grids, next-generation supercomputers and levitating trains - could be much more straightforward in future, as the origin of superconductivity in these materials has finally been identified.Researchers from the University of Cambridge have found that ripples of electrons, known as charge density waves or charge order, create twisted pockets of electrons in these materials, from which superconductivity emerges. The results are published in the June 15th issue of the journal Nature.Low-temperature, or conventional, superconductors were first identified in the early 20th century, but they need to be cooled close to absolute zero (zero degrees on the Kelvin scale, or -273

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DISCLAIMER: I dont own Inuyasha, but if you want to think I do then be my guest.. Walking Through Fire. by: Lara Winner. 888888888888888888888888888888888888. Chapter 5: Checkmate. Silence met the bold youkais pronouncement. Even the birds stopped their twittering as if sensing the lethal tension that strained between the two males at the wolfs words. For Inuyasha it was the final blow to his frayed nerves. After everything hed faced in the last thirty-six hours he was at his limit.. Like fucking hell I will! Inuyasha yelled, placing his hand on the hilt of tetsusaiga in warning to the daft wolf.. I didnt come here to fight mutt. Just hand over my woman and well be on our way. Kouga said, his rakish smile never faltering as he held out a hand to Kagome.. Inuyasha knocked the wolfs hand away and stepped between them to block his view of Kagome. Over my dead body!. Kouga sneered, Are you so eager to die, dog breath?. You can try you bastard but you wont last long against ...

The transition temperature and the critical fields of electron-beam evaporated Nb/Gd/Nb triple layers and Nb/Gd multilayers have been determined by measurements of the electrical resistivity and the dc susceptibility. For constant thickness d(Gd) of the Gd layers, we observe a decrease of T(c) and H(c2 perpendicular-to) with decreasing thickness d(Nb) of Nb layers down to a critical thickness d(c), below which superconductivity is completely destroyed. The parallel critical fields mostly show the square-root temperature dependence near T(c), typical for two-dimensional superconductors. As predicted theoretically, competing pair-breaking mechanisms lead to a nonmonotonic dependence of H(c parallel-to) on d(Nb). We have also studied the dependence T(c)(d(Gd)) with constant d(Nb) and find a decrease of the T(c)(d(Gd)) curve with increasing d(Cd) and a steplike structure at d(Gd) almost-equal-to 20 angstrom. To clarify the nature of this step, the ferromagnetic transition of the Gd films is ...

In the fields of photocatalysis and photovoltaics, ultrafast dynamical processes, including carrier trapping and recombination on material surfaces, are among the key factors that determine the overall energy conversion efficiency. A precise knowledge of these dynamical events on the nanometer (nm) and femtosecond (fs) scales was not accessible until recently. The only way to access such fundamental processes fully is to map the surface dynamics selectively in real space and time. In this study, we establish a second generation of four-dimensional scanning ultrafast electron microscopy (4D S-UEM) and demonstrate the ability to record time-resolved images (snapshots) of material surfaces with 650 fs and â ¼5 nm temporal and spatial resolutions, respectively. In this method, the surface of a specimen is excited by a clocking optical pulse and imaged using a pulsed primary electron beam as a probe pulse, generating secondary electrons (SEs), which are emitted from the surface of the specimen in a ...

In this work, 100 ps time-resolved liquid diffraction experiments on the photoreactions of diiodomercury (HgI2) dissolved in methanol (10 mM) were performed at beamline ID09B, using the optical pump and X-ray probe method. This molecular system has been investigated using the same technique as before, but the transient pathway and subsequent structural dynamics have not been elucidated due to the poor signal-to-noise ratio and limited data analysis method [2]. An optical pulse (267 nm, 2 ps, 986 Hz) triggers impulsive photodissociation of HgI2, followed by subsequent reactions and then the X-ray pulse (100 ps, 0.067 nm, 986 Hz) interrogates the reacting sample by making the diffraction patterns on the CCD detector in a stroboscopic manner for the different time-delays spanning from 100 picosecond to 1 microsecond. The difference diffraction and corresponding radial intensities were extracted from the diffraction pattern and analysed using the so-called global-fitting method which considers ...

American researchers were able to disappear a beam of light, making it reappear in another side, using as slowers 2 clouds of atoms of sodium, separated 1 mm, among them. A light pulse stopped and extinguished in one box is revived from a completely different box in a separate location and sent back on its way. In the actual experiment, a slow light pulse was stopped and stored in one Bose-Einstein condensate (the first box), then revived from a different condensate, 160 μm away. Information was transferred by converting the optical pulse into a travelling matter wave more amenable to manipulation than light. In this case, a first beam of light was thrown against a cloud of atoms of sodium, where after being captured (conversion of light in matter), left a cast of light inside the atoms. A second laser sent to a second near cloud of atoms of sodium, revived the original pulse recapturing the speed of the light with the same form and longitude of wave of the original although something ...

1. I. Walmsley, L. Waxer, and C. Dorrer, The role of dispersion in ultrafast optics, Rev. Sci. Instrum. 72(1), 1-29 (2001). [CrossRef] 2. D. Entenberg, J. Wyckoff, B. Gligorijevic, E. T. Roussos, V. V. Verkhusha, J. W. Pollard, and J. Condeelis, Setup and use of a two-laser multiphoton microscope for multichannel intravital fluorescence imaging, Nat. Protoc. 6(10), 1500-1520 (2011). [CrossRef] [PubMed] 3. M. Müller, J. Squier, R. Wolleschensky, U. Simon, and G. J. Brakenhoff, Dispersion pre-compensation of 15 femtosecond optical pulses for high-numerical-aperture objectives, J. Microsc. 191(2), 141-150 (1998). [CrossRef] [PubMed] 4. P. Xi, Y. Andegeko, L. R. Weisel, V. V. Lozovoy, and M. Dantus, Greater signal, increased depth, and less photobleaching in two-photon microscopy with 10 fs pulses, Opt. Commun. 281(7), 1841-1849 (2008). [CrossRef] 5. R. L. Fork, O. E. Martinez, and J. P. Gordon, Negative dispersion using pairs of prisms, Opt. Lett. 9(5), 150-152 (1984). [CrossRef] ...

The general configuration of the proposed high-speed ADC was described. A train of optical pulses samples the analog signal applied to the optical modulato

TY - JOUR. T1 - Processing of GdBa2Cu3O7-y bulk superconductor and its trapped magnetic field. AU - Nariki, S.. AU - Sakai, N.. AU - Murakami, M.. PY - 2001/8/1. Y1 - 2001/8/1. N2 - Large c-axis oriented GdBa2Cu3O7-y (Gd-123) bulk superconductors, which contain Gd2BaCuO5 (Gd-211) secondary phase and Ag, were melt textured under controlled oxygen partial pressure of 1.0%. Nd-123 was used as a seed crystal for the growth of large-grain bulk. Single-domain Gd-123 samples 32 mm in diameter were successfully fabricated with no macro-sized cracks. The employment of fine starting Gd-211 powders led to a reduction in the mean diameter of Gd-211 particles dispersed in the bulk, which resulted in an improvement in both Jc and field-trapping capability. The trapped magnetic field of the bulk Gd-Ba-Cu-O/Ag made from Gd-211 particles 0.8 μm in diameter reached 1.5 T at 77 K. Furthermore, the trapped magnetic field could be improved by the enlargement of bulk diameter and the optimization of Gd-211 content. ...

books.google.comhttps://books.google.com/books/about/High_Temperature_Superconductors.html?id=8OpAAQAAIAAJ&utm_source=gb-gplus-shareHigh Temperature Superconductors ...

YBa2Cu3O7-x (123) bulk superconductor, which contained uniformly dispersed fine Y2BaCuO5 (211) grains, was fabricated with pre-synthesized Y2BaCuO5, BaO2 and CuO powders by a partial melting process. The size reduction of pre-synthesized 211 powders by fine grinding and low temperature calcination had a positive effect on the homogeneous distribution of fine 211 grains in superconductor bulk materials. The critical current density, Jc, in a magnetic field increased approximately in proportion to the total surface area of 211 grains per unit weight in the 123 phase. When the magnetic field increased, the increase of Jc with the increase of surface area of 211 grains became steep.

The paper presents simulation studies targeting high-power narrow-linewidth emission from semiconductor distributed feedback (DFB) lasers. The studies contain analytic and numerical calculations of emission linewidth, side mode suppression ratio and output power for DFB lasers without phase shifts and with 1 × λ/ 4 and 2 × λ/ 8 phase shifts, taking into account the grating and facets reflectivities, the randomness of the spontaneous emission and the longitudinal photon and carrier density distributions in the laser cavity. Single device structural parameter optimization is generally associated with a trade-off between achieving a narrow linewidth and a high output power. Correlated optimization of multiple structural parameters enables the evaluation of achievable ranges of narrow linewidth and high power combinations. Devices with long cavities and low grating coupling coefficients, κ (keeping κL values below the levels that promote re-broadening), with AR-coated facets and with a ...

2). where Iex is the applied field intensity and α, β, and γ are linear, second-order nonlinear, and third-order nonlinear coefficients, respectively. It is the linear coefficient that controls the linear optical response, such as absorption, reflection, spontaneous emission, and scattering in a weak field. For strong field intensity, the higher-order coefficients in Eq. (2) need to be considered. Higher-order terms contain components of sums and differences of the incident light frequencies and give rise to radiation at new frequencies, such as SHG and THG.. For second-order nonlinear interactions, SHG, hyper-Rayleigh scattering (HRS), sum, and difference-frequency generation are examples [52]. As shown in Figure 1A, SHG involves the transition of the interacting molecules to a higher-energy virtual state by annihilating two incident photons and generating a new photon at twice frequency of them. Because SHG is only allowed with non-centrosymmetric materials, it provides a structural ...

We present measurements of optical correlations from a high-finesse cavity in the intermediate coupling regime, which supports two modes of orthogonal linear polarization. The combination of the two modes with the magnetic structure of 85 Rb atoms allows us to separate photons originating from spontaneous emission from those that come from the driving laser. The second-order intensity correlation function reveals quantum beats at twice the ground-state Larmor frequency for a small applied magnetic field. The beats arise from a coherent ground-state superposition that evolves in time between photon emissions. The frequency of oscillation is sensitive to different parameters of the system; in this talk we show evidence of power-dependent shifts in the oscillation frequencies, visible even at driving intensities of less than one photon on average in the cavity. We discuss a theoretical model that quantitatively includes many of the characteristics of the experiment and shows the frequency shifts ...

where μo is the permeability of free space, ω is the angular frequency, γ is the gyromagnetic ratio, h is Plancks constant, and c is the speed of light. For 1 ml of water at 1 T this translates into spontaneous emission of only 0.024 photons per second, an extremely low number.. There is still considerable controversy as to exactly how the energy absorbed by nuclear spins during NMR is released and induces a current in the receiver coil. The traditional answer photon emission with radio waves is almost certainly incorrect. See the article by David Hoult below for speculations about near field effects, virtual photons, and explanations within the field of quantum electrodynamics (QED ...

Extra resources for Experimental Aspects of Quantum Computing. Example text. Rev. Lett. 84, 2525 (2000). 50. L. Viola, E. Knill, and S. Lloyd, Phys. Rev Lett. 82, 2417 (1999). 51. L. Viola and S. Lloyd, Phys. Rev A. 58, 2733 (1998). 52. A. M. Childs, L L. Chuang, and D. W. Leung, Phys. Rev A 64, 012314 (2001). 53. N. Boulant, T F Havel, M. A. Pravia, and D. G. Cory, Phys. Rev A 67, 042322 (2003). 54. Y Weinstein, T. F Havel, J. Emerson, N. Boulant, M. Saraceno, S. Lloyd, and D. G. Cory, J. Chem. , in press. 55. P Shor, Phys. Rev. A 52, 2493 (1995). 56. A. M. Steane, Phys. The SRT Rabi frequency is given by ^SRT = ^ i ^ 2 / ^ where gt are the resonant Rabi frequencies for the two laser beams respectively driving transitions to the excited state \e). The probabiHty of spontaneous emission from off-resonant excitation to the state \e) during a SRT :n:-pulse decreases with increasing A as However, A cannot be increased indefinitely. In order for SRT to eflfectivly couple H F states and effectively ...