In this experimental work a conception of the phonon spectra of the ${\text{Hg}}_{1-x}{\text{Cd}}_x\text{Te}\left(x=0.06–0.7\right)$ solid solution is presented which explains the presence of additional lines in the region $100–115{\text{cm}}^{-1}$. Data of the optical reflectivity measurements obtained in far and middle infrared regions for eleven comp…

[Phys. Rev. B 82, 014306] Published Fri Jul 30, 2010

We investigated the infrared response of ${\text{LuFe}}_2{\text{O}}_4$ through the series of charge, magnetic, and structural transitions. All vibrational modes couple strongly to the charge order, whereas the LuO zone-folding modes are also sensitive to magnetic order and structural distortion. The dramatic splitting of…

[Phys. Rev. B 82, 014304] Published Tue Jul 27, 2010

Following the Dirac-Frenkel time-dependent variational principle, dynamics of a one-dimensional Holstein polaron is probed by employing the Davydov ${\text{D}}_2$ ansatz with two sets of variational parameters, one for each constituting particle in the exciton-phonon system, and a simplified variant of the Davy…

[Phys. Rev. B 82, 014305] Published Tue Jul 27, 2010

We show that in the few-excitation regime, the classical and quantum time evolution of the inhomogeneous Dicke model for $N$ two-level systems coupled to a single boson mode agree for $N⪢1$. In the presence of a single excitation only, the leading term in an $1/N$ expansion of the classical equations of m…

[Phys. Rev. B 82, 024305] Published Tue Jul 27, 2010

Materials which possess a high lithium ion conductivity are very attractive for battery and fuel cell applications. Hydrogenation of the fast-ion conductor lithium nitride $\left({\text{Li}}_3\text{N}\right)$ leads to the formation of lithium imide $\left({\text{Li}}_2\text{NH}\right)$ and subsequently of lithium amide $\left({\text{LiNH}}_2\right)$. Using ab initio molecular dyna…

[Phys. Rev. B 82, 024304] Published Mon Jul 26, 2010

We analyze a number of proposed explanations for spectroscopic anomalies observed in atomic hydrogen defects embedded in a solid molecular hydrogen matrix. In particular, we critically evaluate the possibility that these anomalies are related to Bose-Einstein condensation (both global and local). Fo…

[Phys. Rev. B 82, 014303] Published Fri Jul 23, 2010

We present a family of exact analytic solutions for nonlinear quantum dynamics of a two-level system (TLS) subject to a periodic-in-time external field. In constructing the exactly solvable models, we use a “reverse engineering” approach where the form of external perturbation is chosen to preserve …

[Phys. Rev. B 82, 024303] Published Thu Jul 22, 2010

We present measurements of transmission and reflection spectra of a microwave photonic crystal composed of 874 metallic cylinders arranged in a triangular lattice. The spectra show clear evidence of a Dirac point, a characteristic of a spectrum of relativistic massless fermions. In fact, Dirac point…

[Phys. Rev. B 82, 014301] Published Fri Jul 16, 2010

The phase and group velocities are considered for the eight lowest plate acoustic waves (PAWs) propagating in a periodically poled lithium niobate (PPLN) wafer. The PPLN turns to be a specific multidomain phononic superlattice (MPS) that has identical mechanical properties throughout the crystalline…

[Phys. Rev. B 82, 014302] Published Fri Jul 16, 2010

The hexagonal and orthorhombic form of lithium borohydride, ${\text{LiBH}}_4$, are investigated by temperature and frequency-dependent nuclear magnetic resonance (NMR) spectroscopy. The local electronic structure and microscopic diffusion parameters are determined by recording both ${}^{6,7}\text{L}\text{i}$ NMR spectra and spin-la…

[Phys. Rev. B 82, 020301(R)] Published Fri Jul 16, 2010

The first ab initio calculations using ultrasoft pseudopotentials within the local-density approximation in superconducting ${\text{ZrB}}_{12}$ are reported, together with an inelastic neutron scattering study of its lattice dynamics. As in previously studied rare-earth dodecaborides, the phonon spectra are mainl…

[Phys. Rev. B 82, 024302] Published Thu Jul 08, 2010

Using optical spectroscopy, we investigated the electrodynamic properties of $\text{Nb}:{\text{SrTiO}}_3/{\text{SrTiO}}_3$ superlattices. In these superlattices, a large enhancement of the Seebeck coefficient $\left(S\right)$ has been reported with decreasing $\text{Nb}:{\text{SrTiO}}_3$ layer thickness [H. Ohta et al., Nature Mater. 6, 129 (2007)]. By analy…

[Phys. Rev. B 82, 024301] Published Wed Jul 07, 2010

In a femtosecond pump-probe experiment the pump pulse injects a modest density of free carriers by multiphoton absorption. Measuring the nonlinear absorption of the probe pulse we observe exciton-seeded multiphoton ionization. The excitons self-trap in ${\text{SiO}}_2$ in $<300\text{fs}$ following free-carrier injec…

[Phys. Rev. B 81, 212301] Published Tue Jun 29, 2010

Molecular-dynamics method is used to study the influence of mass ratio of anions and cations on the phonon spectrum of the crystal with NaCl structure and on the conditions of existence and properties of gap discrete breathers (DBs). We show that DBs can be easily excited when the mass ratio of ligh…

[Phys. Rev. B 81, 214306] Published Tue Jun 29, 2010

We predict the bulk thermal conductivity of Lennard-Jones argon and Stillinger-Weber silicon using the Green-Kubo (GK) and direct methods in classical molecular dynamics simulations. While system-size-independent thermal conductivities can be obtained with less than 1000 atoms for both materials usi…

[Phys. Rev. B 81, 214305] Published Mon Jun 21, 2010

In the skutterudite compounds the anharmonic “rattling” oscillations of $4f$-guest ions in the surrounding ${\text{Sb}}_{12}$ host cages are found to have significant influence on the low-temperature properties. Recently specific-heat analysis of $\text{Pr}{\left({\text{Os}}_{1-x}{\text{Ru}}_x\right)}_4{\text{Sb}}_{12}$ has shown that the energy of crystalline electric f…

[Phys. Rev. B 81, 224305] Published Fri Jun 18, 2010

There have been several reports of phase-dependent noise in time-domain reflectivity studies of optical phonons excited by femtosecond laser pulses in semiconductors, semimetals, and superconductors. It was suggested that such behavior is associated with the creation of squeezed phonon states althou…

[Phys. Rev. B 81, 224304] Published Thu Jun 17, 2010

We present a combined experimental and theoretical study on the rotational motion of the ${\left({\text{BH}}_4\right)}^{-}$ ions in alkaline tetrahydroborides $M{\text{BH}}_4$, $M=\left(\text{Li},\text{Na},\text{K}\right)$. The ${\text{BH}}_4$ motions are thermally activated and characterized by activation energies in the order of 0.1 eV, typical frequencies are in the terahertz rang…

[Phys. Rev. B 81, 214304] Published Tue Jun 15, 2010

We report a systematic measurement of the electron-phonon thermalization time scale as a function of the sample base temperature in Ni using femtosecond electron diffraction. A strong temperature dependence of this time scale has been observed in the vicinity of the Curie point. By assuming that ult…

[Phys. Rev. B 81, 220301(R)] Published Fri Jun 11, 2010

We investigate theoretically the propagation of acoustic waves in a two-dimensional array of cylindrical pillars on the surface of a semi-infinite substrate. Through the computation of the band structure of the periodic array and of the transmission of waves through a finite length array, we show th…

[Phys. Rev. B 81, 214303] Published Thu Jun 10, 2010

A simple and robust fitting procedure is presented for determining the three elastic constants of a cubic crystal from surface Brillouin scattering measurements carried out in the $⟨100⟩$ and $⟨110⟩$ directions in a (001) surface. The input data utilized are the Rayleigh surface wave velocity, the Lamb …

[Phys. Rev. B 81, 224303] Published Thu Jun 10, 2010

We calculate root-mean-square deviations from equilibrium for atoms in a two-dimensional crystal with local (e.g., covalent) bonding between close neighbors. Large-scale Monte Carlo calculations are in good agreement with analytical results obtained in the harmonic approximation. When motion is rest…

[Phys. Rev. B 81, 214302] Published Wed Jun 09, 2010

We discuss the quench dynamics near a quantum critical point focusing on the sine-Gordon model as a primary example. We suggest a unified approach to sudden and slow quenches, where the tuning parameter $\lambda \left(t\right)$ changes in time as $\lambda \left(t\right)\sim \upsilon t^r$, based on the adiabatic expansion of the excitation probability …

[Phys. Rev. B 81, 224301] Published Tue Jun 08, 2010

The lattice dynamics of the ferromagnetic spinel ${\text{CuCr}}_2{\text{Se}}_4$ $\left(T_{\text{C}}=430\text{K}\right)$ was studied experimentally by measuring the Raman spectra and theoretically by calculation of zone center phonon frequencies within a shell model. All Raman allowed modes $\left(A_{1g}+E_g+3F_{2g}\right)$ were identified and assigned to specific atomi…

[Phys. Rev. B 81, 224302] Published Tue Jun 08, 2010

For the warm dense-matter regime, we have examined the effects on the equation of state, conductivity, and optical properties of the introduction of a metal impurity (Al) into a poorly conducting mixture $\left({\text{CH}}_2\right)$ by means of quantum molecular-dynamics simulations employing temperature-dependent density…

[Phys. Rev. B 81, 214301] Published Thu Jun 03, 2010

Using the mapping of the Fokker-Planck description of classical stochastic dynamics onto a quantum Hamiltonian, we argue that a dynamical glass transition in the former must have a precise definition in terms of a quantum phase transition in the latter. At the dynamical level, the transition corresp…

[Phys. Rev. B 81, 184303] Published Wed May 26, 2010

Zinc oxide is a key material for optoelectronic applications, whose transport properties are typically dominated by the lattice vibrations. We report here the phonon-dispersion relations of wurtzite ZnO at 10 K, as determined by using inelastic neutron scattering. The experimental data are analyzed …

[Phys. Rev. B 81, 174304] Published Mon May 24, 2010

Vibrational properties of anatase titanium dioxide single crystal are thoroughly investigated by means both of experimental and theoretical approaches. Polarized Raman-scattering experiments were carried out at room temperature in backscattering geometry on a microcrystalline anatase sample under di…

[Phys. Rev. B 81, 174305] Published Mon May 24, 2010

The quantum state of the hydrogen atom that is trapped at the most stable octahedral interstitial site in the ${\text{LaNi}}_5$ crystal is determined. A three-dimensional potential-energy surface for the hydrogen atom around the $3f$ site is obtained by applying first-principles electronic-structure calculations.…

[Phys. Rev. B 81, 184302] Published Thu May 20, 2010

We report on the effect of grain size on the ionic conductivity of yttria-stabilized zirconia samples synthesized by ball milling. Complex impedance measurements, as a function of temperature and frequency are performed on $10\text{mol}\mathrm{\%}$ yttria-stabilized zirconia nanocrystalline samples with grain sizes …

[Phys. Rev. B 81, 184301] Published Mon May 10, 2010

We developed a method to calculate the anharmonic free energy without requiring any adjustable parameter. The requisite computations are first-principles quasiharmonic calculations plus an additional Canonical (NVT) ensemble first-principles molecular-dynamics simulation and, therefore, are affordab…

[Phys. Rev. B 81, 172301] Published Fri May 07, 2010

We investigate the parametrization and optimization of thermal conductivity in silicon-germanium alloy nanowires by the cluster-expansion technique. ${\text{Si}}_{1-x}{\text{Ge}}_x$ nanowires are of interest for thermoelectric applications and the reduction in lattice thermal conductivity $\left({\kappa }_L\right)$ is desired for enhancing the …

[Phys. Rev. B 81, 174303] Published Fri May 07, 2010

First-principles density-functional theory and lattice-dynamics calculations were performed to study the vibrational dynamics and related observables of the ternary compounds ${\text{Ca}}_{1-x}{\text{Fe}}_4{\text{Sb}}_{12}$, ${\text{Sr}}_{1-x}{\text{Fe}}_4{\text{Sb}}_{12}$, ${\text{Ba}}_{1-x}{\text{Fe}}_4{\text{Sb}}_{12}$. and ${\text{Yb}}_{1-x}{\text{Fe}}_4{\text{Sb}}_{12}$. The calculation results are supported by experimental data, which…

[Phys. Rev. B 81, 174302] Published Wed May 05, 2010

Thermal properties of ternary carbides with composition ${\text{Ti}}_3{\text{SiC}}_2$, ${\text{Ti}}_3{\text{AlC}}_2$, and ${\text{Ti}}_3{\text{GeC}}_2$ were studied using the first-principles phonon calculations. The thermal expansions, the heat capacities at constant pressure, and the isothermal bulk moduli at finite temperatures were obtained under the quasiharm…

[Phys. Rev. B 81, 174301] Published Tue May 04, 2010

We study a composite quantum quench of the energy gap and the interactions in the interacting ${\varphi }^4$ model using a self-consistent approximation. First we review results for free theories where a quantum quench of the energy gap or mass leads for long times to stationary behavior with thermal characteri…

[Phys. Rev. B 81, 134305] Published Fri Apr 30, 2010

Electromagnetically induced transparency (EIT) is reported in a solid-state material doped with erbium ions. In this paper we introduce the spectroscopic investigations we have conducted in order to identify the adequate $\Lambda$-like three-level systems in ${\text{Er}}^{3+}:{\text{Y}}_2{\text{SiO}}_5$ crystal, relevant for the demonstrati…

[Phys. Rev. B 81, 144303] Published Fri Apr 30, 2010

Hydrogen hopping paths in ${\text{LaNi}}_5\text{H}$ solid solution were analyzed via first-principles calculations. Potential energy surfaces were determined for hydrogen on the plane with hydrogen sites $6m$, $12o$, and $4h$ and on the plane with hydrogen sites $12n$, $3f$, and $6i$. From the zero-point vibration energy along th…

[Phys. Rev. B 81, 134304] Published Mon Apr 26, 2010

The phonon states of iron atoms in the easy-axis aligned $L{1}_0\text{-FePt}$ nanoparticles were investigated using ${}^{57}\text{F}\text{e}$ nuclear-resonant inelastic scattering. It was revealed that the phonon density of states (PDOS) in the $L{1}_0\text{-FePt}$ has a pronounced anisotropy. To study the results from a theoretical point of v…

[Phys. Rev. B 81, 132302] Published Thu Apr 22, 2010

We have studied the lattice dynamics of crystalline ${\text{TiO}}_2$ using density-functional perturbation theory and the local-density approximation in a plane-wave pseudopotential formalism at equilibrium and uniaxially strained geometries. We present well-converged calculations of the dispersion curves, whic…

[Phys. Rev. B 81, 134303] Published Wed Apr 21, 2010

We have measured polarized Raman scattering spectra of the ${\text{Fe}}_{1-x}{\text{Co}}_x{\text{Sb}}_2$ and ${\text{Fe}}_{1-x}{\text{Cr}}_x{\text{Sb}}_2$ $\left(0\le x\le 0.5\right)$ single crystals in the temperature range between 15 and 300 K. The highest energy $B_{1g}$ symmetry mode shows significant line asymmetry due to phonon-mode coupling-width electronic background. The coupling …

[Phys. Rev. B 81, 144302] Published Fri Apr 16, 2010

We investigate the Kondo model with time-dependent couplings that are periodically switched on and off. On the Toulouse line we derive exact analytical results for the spin dynamics in the steady state that builds up after an infinite number of switching periods. Remarkably, the universal long-time …

[Phys. Rev. B 81, 144301] Published Fri Apr 09, 2010

The study of the transient light-induced absorption in thermally reduced, periodically poled lithium niobate doped with Y uncovers the simultaneous action of the ${\text{Nb}}_{\text{Li}}^{4+}:{\text{Nb}}_{\text{Nb}}^{4+}$ bipolaron and ${\text{O}}^{-}$ hole polaron relaxation in the blue and near-infrared spectral range. The findings can be comprehensively e…

[Phys. Rev. B 81, 132301] Published Wed Apr 07, 2010

${\text{Cd}}_2{\text{Re}}_2{\text{O}}_7$ single crystals exhibit an amorphouslike lattice thermal conductivity, ${\kappa }_{\text{latt}}$. At temperatures about twice the Debye temperature, the phonon mean-free path approaches the value of the average Cd-Cd spacing while the specific heat is at values notably lower than the classical Dulong-Petit lim…

[Phys. Rev. B 81, 134302] Published Wed Apr 07, 2010

While the thermal conductivity of the filled skutterudites has been of great interest it had not been calculated within a microscopic theory. Here a central force, Guggenheim-McGlashen, model with parameters largely extracted from first-principles calculations and from spectroscopic data, specific t…

[Phys. Rev. B 81, 134301] Published Mon Apr 05, 2010

We measured the magnetoinfrared response of the quasi-one-dimensional quantum Heisenberg antiferromagnet $\text{Cu}\left(\text{pyz}\right){\left({\text{NO}}_3\right)}_2$ to investigate local lattice distortions through the field-driven transition to the fully polarized state. This magnetic quantum critical transition involves changes in the out-of-p…

[Phys. Rev. B 81, 104307] Published Wed Mar 31, 2010

The time evolution of magnons subject to a time-dependent microwave field is usually described within the so-called “S-theory,” where kinetic equations for the distribution function are obtained within the time-dependent Hartree-Fock approximation. To explain the recent observation of “Bose-Einstein…

[Phys. Rev. B 81, 104308] Published Wed Mar 31, 2010

We calculate the nonequilibrium dynamic evolution of a one-dimensional system of two-component fermionic atoms after a strong local quench by using a time-dependent spin-density-functional theory. The interaction quench is also considered to see its influence on the spin-charge separation. It is sho…

[Phys. Rev. B 81, 104306] Published Tue Mar 30, 2010

Low-temperature diffuse reflectance infrared spectroscopy is used to measure the quantum dynamics of molecular hydrogen and its isotopologues adsorbed in the microporous material MOF-74. At least two distinct adsorption sites are revealed by increasing the concentration of ${\text{H}}_2$ within the material and…

[Phys. Rev. B 81, 104305] Published Mon Mar 29, 2010

The coupled electronic and vibrational dynamics of exciton self-trapping are studied in the quasi-one-dimensional material $\left[\text{Pt}{\left(\text{en}\right)}_2\right]\left[\text{Pt}{\left(\text{en}\right)}_2{\text{Br}}_2\right]\cdot {\left({\text{PF}}_6\right)}_4$ ($\text{en}=\text{ethylenediamine}$) using femtosecond impulsive excitation techniques. We report transient absorption measurements at 77 K that are modulated by a …

[Phys. Rev. B 81, 094302] Published Mon Mar 22, 2010

We study ballistic thermal transport in three-terminal atomic nanojunctions by the nonequilibrium Green’s function method. We find that there is ballistic thermal rectification in asymmetric three-terminal structures because of the incoherent phonon scattering from the control terminal. With spin-ph…

[Phys. Rev. B 81, 100301(R)] Published Mon Mar 22, 2010

We report on a comprehensive first-principles investigation of Li diffusion in spinel ${\text{Li}}_{1+x}{\text{Ti}}_2{\text{O}}_4$, a viable anode material for Li-ion batteries. Concentration dependent diffusion coefficients are calculated by applying kinetic Monte Carlo simulations to a first-principles parametrized cluster expansi…

[Phys. Rev. B 81, 104304] Published Mon Mar 22, 2010

The dynamical critical exponent $z$ is a fundamental quantity in characterizing quantum criticality, and it is well-known that the presence of dissipation in a quantum model has significant impact on the value of $z$. Studying quantum Ising spin models using Monte Carlo methods, we estimate the dynamica…

[Phys. Rev. B 81, 104302] Published Tue Mar 16, 2010

Spectral properties of coupled cavity arrays in one dimension are investigated by means of the variational cluster approach. Coupled cavity arrays consist of two distinct “particles,” namely, photons and atomiclike excitations. Spectral functions are evaluated and discussed for both particle types. …

[Phys. Rev. B 81, 104303] Published Tue Mar 16, 2010

In this work we use analytic and numerical techniques to construct optimal, nearly reflectionless boundary layers for lattice dynamics by tuning the mass, stiffness, and damping of those layers. Using a one-dimensional nearest-neighbor chain as a model system, we obtain analytical results for the lo…

[Phys. Rev. B 81, 094301] Published Fri Mar 05, 2010

Lattice dynamics calculations and high-pressure Raman scattering study of ${\text{Bi}}_2{\text{W}}_2{\text{O}}_9$, which is an $m=2$ member of the cation-deficient bismuth layered Aurivillius family of compounds, are presented. These studies showed the onset of two reversible second-order phase transitions near 2.8 and 4.8 GPa. The …

[Phys. Rev. B 81, 104301] Published Fri Mar 05, 2010

Although $B2\text{-NiAl}$ has one of the simplest crystal structures of any intermetallic compound, its atomic transport mechanisms are complex and remain poorly understood. Here, we report on a first-principles study of diffusion in $B2\text{-NiAl}$ that simultaneously accounts for all relevant hop mechanisms in kin…

[Phys. Rev. B 81, 064303] Published Fri Feb 26, 2010

A model is presented that interprets both electron capture (trapping) and ionization (detrapping) processes in insulators. It emphasizes the importance of the electron-phonon interactions on the electronic transitions involving defect states. These electronic transitions are accompanied by multiphon…

[Phys. Rev. B 81, 054307] Published Thu Feb 25, 2010

We show that the low-frequency modes of a sub-Ohmic bosonic heat bath generate an effective dynamical asymmetry for an intrinsically symmetric quantum spin-1/2. An initially fully polarized spin first decays toward a quasiequilibrium determined by the dynamical asymmetry, thereby showing coherent da…

[Phys. Rev. B 81, 054308] Published Thu Feb 25, 2010

In quasicrystals, the phason degree of freedom and the inherent anharmonic potentials lead to complex dynamics, which cannot be described by the usual phonon modes of motion. We have constructed simple one-dimensional model systems, the dynamic Fibonacci chain, and approximants thereof. They allow u…

[Phys. Rev. B 81, 064302] Published Thu Feb 25, 2010

We investigate the steady-state heat current in two- and three-dimensional disordered harmonic crystals in a slab geometry connected at the boundaries to stochastic white-noise heat baths at different temperatures. The disorder causes short-wavelength phonon modes to be localized so the heat current…

[Phys. Rev. B 81, 064301] Published Wed Feb 24, 2010

The effective vibrational density of states (VDOS) has been derived from inelastic neutron-scattering data, for isotopically substituted $\text{Si}{{}^{18}\text{O}}_2$ and $\text{Si}{{}^{16}\text{O}}_2$ glasses, to gain information about the relative contribution to the Si and O partial VDOS. This is a necessary point of comparison for vibratio…

[Phys. Rev. B 81, 060301(R)] Published Mon Feb 22, 2010

We discuss a technique for solving the Landau-Zener (LZ) problem of finding the probability of excitation in a two-level system. The idea of time reversal for the Schrödinger equation is employed to obtain the state reached at the final time and hence the excitation probability. Using this method, w…

[Phys. Rev. B 81, 054306] Published Fri Feb 19, 2010

The semiclassical equations of motion for a Bloch electron include an anomalous velocity term analogous to a $k$-space “Lorentz force,” with the Berry connection playing the role of a vector potential. By examining the adiabatic evolution of Bloch states in a monotonically increasing vector potential,…

[Phys. Rev. B 81, 052303] Published Thu Feb 18, 2010

Using a one-dimensional jellium model and standard beam theory we calculate the spring constant of a vibrating nanowire cantilever. By using the asymptotic energy eigenvalues of the standing electron waves over the nanometer-sized cross-section area, the change in the grand canonical potential is ca…

[Phys. Rev. B 81, 054304] Published Tue Feb 16, 2010

For a Bose-Hubbard dimer, we study quenches of the site energy imbalance, taking a highly asymmetric Hamiltonian to a fully symmetric one. The ramp is carried out over a finite time that interpolates between the instantaneous and adiabatic limits. We provide results for the excess energy of the fina…

[Phys. Rev. B 81, 054305] Published Tue Feb 16, 2010

The thermal contact resistance at a highly polished single-crystal silicon (111)/liquid helium interface has been directly measured from 0.4 to 2.1 K using a single experimental cell. A thermal analysis is presented using the thermal conductivity of the Si which is simultaneously measured. The effec…

[Phys. Rev. B 81, 054303] Published Mon Feb 08, 2010

We study the time-dependent transport of heat in a nanoscale thermal switch. The switch consists of left and right leads that are initially uncoupled. During switch on the coupling between the leads is abruptly turned on. We use the nonequilibrium Green’s function formalism and numerically solve the…

[Phys. Rev. B 81, 052302] Published Fri Feb 05, 2010

The detailed characterization of the dynamical behavior of an oscillating cantilever is a crucial task in many applications of scanning probe microscopy, force spectroscopy, and cantilever based biosensors. In the present work we considered a direct and localized excitation of the cantilever obtaine…

[Phys. Rev. B 81, 054302] Published Thu Feb 04, 2010

A dynamical nonequilibrium temperature has been proposed to describe relaxational equations for the heat flux. This temperature provides an alternative description to the Maxwell-Cattaneo equation. In the linear regime and in bulk systems both descriptions are equivalent but this is not so when nonl…

[Phys. Rev. B 81, 054301] Published Wed Feb 03, 2010

We propose a notable scaling theory for general quantum breakdown phenomena. We show, taking Landau-Zener-type breakdown as a particular example that the breakdown phenomena can be viewed as a quantum phase transition for which the scaling Ansatz is developed. Its application to Zener-type breakdown…

[Phys. Rev. B 81, 052301] Published Mon Feb 01, 2010

Yttrium substitution in ${\text{Eu}}_{1-x}{\text{Y}}_x{\text{MnO}}_3$ allows a quasicontinuous tuning of the lattice and magnetic properties of this multiferroic manganite without magnetic interference of rare-earth ions. In order to investigate the composition dependence of the spin-phonon coupling we employ polarized Raman scatter…

[Phys. Rev. B 81, 024304] Published Wed Jan 27, 2010

The local dynamics of crystalline germanium has been investigated by molecular-dynamics simulations. The radial distribution functions of the first six coordination shells, as well as their parallel and perpendicular mean-square relative displacements, have been determined as a function of temperatu…

[Phys. Rev. B 81, 012304] Published Fri Jan 22, 2010

We study the dynamical response of a system to a sudden change of the tuning parameter $\lambda$ starting (or ending) at the quantum critical point. In particular, we analyze the scaling of the excitation probability, number of excited quasiparticles, heat and entropy with the quench amplitude, and the syst…

[Phys. Rev. B 81, 012303] Published Tue Jan 19, 2010

The dynamical properties of protonic conductor ${\text{K}}_3\text{H}{\left({\text{SeO}}_4\right)}_2$ were examined by Brillouin scattering. Both longitudinal-acoustic modes ($c_{33}$ and $c_{11}$) and a transversal mode $\left(c_{44}\right)$ monotonously depend on temperature, and no soft mode was observed. A central mode with a width about 6 GHz was observed above p…

[Phys. Rev. B 81, 012301] Published Tue Jan 12, 2010

We propose a practical realization of a field-effect transistor for phonons. Our device is based on a single ionic polymeric molecule and it gives modulations as large as $-25\mathrm{\%}$ in the thermal conductance for feasible temperatures and electric field magnitudes. Such effect can be achieved by reversibl…

[Phys. Rev. B 81, 012302] Published Tue Jan 12, 2010

Deep inelastic neutron-scattering experiments using indirect time-of-flight spectrometers have reported a smaller cross section for the hydrogen atom than expected from conventional scattering theory. Typically, at large momentum transfers, a deficit of $20–40\%$ in the neutron-scattering intensity ha…

[Phys. Rev. B 81, 024303] Published Tue Jan 12, 2010

We present a simple but accurate scheme to compute the thermodynamic properties of crystalline solids in a wide range of pressure and temperature based on ab initio calculations. Compared to the method based on ab initio thermodynamic-integration techniques, our approach can reduce dramatically the …

[Phys. Rev. B 81, 014301] Published Mon Jan 11, 2010

We have determined the ballistic heat transport relation of $V^2=C\left(T_m-T\right)$ in nanocontacts involving the bias voltage $V$, the ambient temperature $T$, and the maximum temperature $T_m$ inside the contact by exploiting the ordering temperature of a magnetic solid as a natural thermometer. The relation has been…

[Phys. Rev. B 81, 020301(R)] Published Thu Jan 07, 2010

The phonon structure of antiferromagnetic ${\text{Bi}}_2{\text{Fe}}_4{\text{O}}_9$ (space group $Pbnm$ No. 55, $T_N\approx 240\text{K}$) was studied theoretically by calculations of lattice dynamics and experimentally between 10 and 300 K by polarized Raman spectroscopy. Most of the $12A_g+12B_{1g}+9B_{2g}+9B_{3g}$ Raman modes were unambiguously identified. St…

[Phys. Rev. B 81, 024302] Published Tue Jan 05, 2010

Spectral properties of the two-dimensional Bose-Hubbard model, which emulates ultracold gases of atoms confined in optical lattices, are investigated by means of the variational cluster approach. The phase boundary of the quantum phase transition from Mott phase to superfluid phase is calculated and…

[Phys. Rev. B 81, 024301] Published Mon Jan 04, 2010

An approach to correlated dynamics of quantum nuclei and electrons both in dynamical interaction with external environments is presented. This stochastic quantum molecular dynamics rests on a theorem that establishes a one-to-one correspondence between the total ensemble-averaged current density of …

[Phys. Rev. B 80, 212303] Published Wed Dec 30, 2009

A generalized Langevin equation with quantum heat baths [quantum molecular dynamics (QMD)] for thermal transport is derived with the help of nonequilibrium Green’s function (NEGF) formulation. The exact relationship of the quasiclassical approximation to NEGF is demonstrated using Feynman diagrams o…

[Phys. Rev. B 80, 224302] Published Tue Dec 22, 2009

The phonon density of states (DOS) and phonon entropy of $B2$ FeAl were determined as functions of the Fe site vacancy concentration using several scattering techniques and were computed from first principles. Measurements at elevated temperature and pressure were performed to explore volume effects, …

[Phys. Rev. B 80, 214303] Published Mon Dec 21, 2009

We present a detailed study of the non-Markovian two-state system dynamics for the regime of incoherent quantum tunneling. Using perturbation theory in the system tunneling amplitude $\Delta$, and in the limit of strong system-bath coupling, we determine the short-time evolution of the reduced density matr…

[Phys. Rev. B 80, 214302] Published Fri Dec 18, 2009

The polarized Raman spectra of ${\text{MnWO}}_4$ single crystals were studied between 5 and 300 K. All $8A_g+10B_g$ Raman active modes were identified and assigned to definite atomic motions in close comparison with the frequencies and eigenvectors predicted by shell model calculations. No detectable phonon anomali…

[Phys. Rev. B 80, 212302] Published Thu Dec 17, 2009

Starting from an empirical force constant model of valence interactions and calculating by Ewald’s method the ion-ion force constants, we derive the dynamical matrix for a monolayer crystal of hexagonal boron nitride (h-BN). The phonon dispersion relations are calculated. The interplay between valen…

[Phys. Rev. B 80, 224301] Published Thu Dec 17, 2009

An analytical approach is developed to investigate the phase transitions and the dynamical behaviors in dissipative two-state systems in a unified method for different bath indices with the view of understanding the effects of environments and tunneling on the systems. Analytic expressions of the cu…

[Phys. Rev. B 80, 214301] Published Wed Dec 09, 2009

We present a theory for Bloch wave propagation in damped elastic media. We expand the eigenvalue problem governing the dispersion relation using a set of Bloch mode eigenvectors at each wave-vector point. With the assumption of Rayleigh damping, this decomposition allows us to derive the band struct…

[Phys. Rev. B 80, 212301] Published Wed Dec 02, 2009

We provide a methodology for generating interatomic potentials for use in classical molecular-dynamics simulations of atomistic phenomena occurring at energy scales ranging from lattice vibrations to crystal defects to high-energy collisions. A rigorous method to objectively determine the shape of a…

[Phys. Rev. B 80, 174302] Published Wed Nov 25, 2009

We demonstrate a method to design nonresonant acoustic composite metamaterials made of periodic arrangements of highly subwavelength unit cells composed of one or more inclusions embedded in a fluid. The inclusion geometry determines the degree of anisotropy and effective material parameters, and it…

[Phys. Rev. B 80, 174303] Published Wed Nov 25, 2009

The physics of heat conduction in layered, anisotropic crystals is probed by measurements of the cross-plane elastic constant $C_{33}$ and thermal conductivity $\Lambda$ of muscovite mica as a function of hydrostatic pressure. Picosecond interferometry and time-domain thermoreflectance provide high-precision mea…

[Phys. Rev. B 80, 180302(R)] Published Fri Nov 20, 2009

The phonon density of states (DOS) of ${\text{La}}_{3-x}{\text{Te}}_4$ compounds $\left(x=0.0,0.18,0.32\right)$ was measured at 300, 520, and 780 K, using inelastic neutron scattering. A significant stiffening of the phonon DOS and a large broadening of features were observed upon introduction of vacancies on La sites (increasing $x$). H…

[Phys. Rev. B 80, 184302] Published Thu Nov 19, 2009

We present a thermal transport phenomenon, a unidirectional selection-rule blockade, and show how it produces unprecedented rectification of bosonic heat flow through molecular or mesoscopic quantum systems. Rectification arises from the quantization of energy levels of the conduction element and se…

[Phys. Rev. B 80, 180301(R)] Published Wed Nov 18, 2009

We address the issue of interaction between zero-point vacancies in solid ${}^4\text{H}\text{e}$ as described within the shadow wave function model. Applying the reversible-work method and taking into account finite-size effects, we obtain a zero-point monovacancy concentration of $\left(2.03\pm 0.02\right)\times {10}^{-3}$, which is slightly h…

[Phys. Rev. B 80, 172302] Published Mon Nov 16, 2009

We have performed a parametric study of self-propagating chain reactions along a one-dimensional bead-spring array. The coupling between beads is modeled using harmonic and anharmonic Fermi-Pasta-Ulam (FPU)-$\beta$ and ${\phi }^4$ potentials. The parameters that define the system are the activation energy $\left(E_a\right)$ of …

[Phys. Rev. B 80, 174301] Published Fri Nov 13, 2009

We study thermal transport in anisotropic Heisenberg spin chains using the quantum master equation. It is found that thermal rectification changes sign when the external homogeneous magnetic field is varied. This reversal also occurs when the magnetic field becomes inhomogeneous. Moreover, we can tu…

[Phys. Rev. B 80, 172301] Published Thu Nov 12, 2009

A quantitative description is suggested for electrode polarization, an ubiquitous phenomenon which takes place at the interface between a metallic and an ionic conductor and results in an increase by many orders of magnitude in the net dielectric response of the sample cell. Based on the fact that d…

[Phys. Rev. B 80, 184301] Published Thu Nov 05, 2009

We describe a tunable slow light device based on a photonic-crystal with a mechanically adjustable coupled-resonator optical waveguide structure. The lateral energy confinement is implemented along a lattice shear defect with the group velocity actively controlled by shifting the shear along the def…

[Phys. Rev. B 80, 134305] Published Thu Oct 29, 2009

Extensive equilibrium molecular-dynamics simulations have been performed to investigate thermal-conduction mechanisms via the Green-Kubo approach for fully occupied type I, II, and H methane hydrates, in addition to ice Ih and a hypothetical empty type I hydrate structure. The TIP4P water model was …

[Phys. Rev. B 80, 134306] Published Thu Oct 29, 2009

A time-convolutionless master equation is established for studying the dynamics of a narrow-band exciton coupled with optical phonons. Within the nonadiabatic weak-coupling limit, the diagonal hypothesis works quite well so that the exciton-phonon dynamics is mainly governed by the so-called time-de…

[Phys. Rev. B 80, 144304] Published Fri Oct 23, 2009