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Bulk dc resistivity and dielectric constant measurements with temperature and frequency have been performed in LaMn_{1-x}Fe_xO_3 (0 <= x <= 1.0) as a result of Fe substitution both for the as-synthesized and oxygen annealed samples.…
We examine coherent phonons in a strongly driven sample of optimally-doped high temperature superconductor YBa$_2$Cu$_3$O$_{7-\delta}$. We observe a non-linear lattice response of the 4.5\,THz copper-oxygen vibrational mode at high…
We construct a many-body model Hamiltonian to capture how phonons renormalize exciton binding as a function of temperature. By using the GW approximation and density functional perturbation theory, we are able to parameterize this…
Ferropericlase (Fp), (Mg$_\mathrm{1-x}$Fe$_\mathrm{x}$)O, is the second most abundant phase in the Earths lower mantle. At relevant pressure-temperature conditions, iron in Fp undergoes a high spin (HS), S=2, to low spin (LS), S=0, state…
The understanding and modeling of inelastic scattering of thermal phonons at a solid/solid interface remain an open question. We present a fully quantum theoretical scheme to quantify the effect of anharmonic phonon-phonon scattering at an…
We report the investigation of electronic collective modes in rare-earth-based magnets (Mo$_{2/3}$RE$_{1/3}$)$_2$AlC (also known as RE-$i$-MAX phases), where RE=Gd, Yb, and Dy, using single crystal samples. A detailed investigation of the…
Phonon anharmonicity is ubiquitous in real materials and is crucial for understanding thermal properties and phase stability. In this work, we show that anharmonic phonon modes can be obtained by maximizing their vibration stability during…
Raman scattering in the three-dimensional Dirac semimetal Cd3As2 shows an intricate interplay of electronic and phonon degrees of freedom. We observe resonant phonon scattering due to interband transitions, an anomalous anharmonicity of…
Barium zirconate (BaZrO$_3$) is one of the very few perovskites that is claimed to retain an average cubic structure down to \SI{0}{\K}, while being energetically very close to an antiferrodistortive phase obtained by condensation of a soft…
We report investigation of phonons and oxygen diffusion in Bi2O3 and (Bi0.7Y0.3)2O3. The phonon spectra have been measured in Bi2O3 at high temperatures up to 1083 K using inelastic neutron scattering. Ab-initio calculations have been used…
We report on the lattice evolution of BiFeO3 as function of temperature using far infrared emissivity, reflectivity, and X-ray absorption local structure. A power law fit to the lowest frequency soft phonon in the magnetic ordered phase…
We report temperature evolution of coherently excited acoustic and optical phonon dynamics in superconducting iron pnictide single crystal Ca(Fe_0.944Co_0.056)_2As_2 across the spin density wave transition at T_SDW ~ 85 K and…
High-harmonic generation in solids has emerged as a powerful probe of ultrafast electron dynamics and lattice motion, and recent theoretical work has suggested that thermally driven lattice fluctuations can act as an effective source of…
The thermal and electrical transport properties of single-crystalline LaBe$_{13}$ have been investigated by specific-heat ($C$) and electrical-resistivity ($\rho$) measurements. The specific-heat measurements in a wide temperature range…
We report the pressure and temperature dependence of the phonon density-of-states in superconducting Ca0.6Na0.4Fe2As2 (Tc=21 K) and the parent compound CaFe2As2, using inelastic neutron scattering. We observe no significant change in the…
Extensive inelastic neutron scattering measurements of phonons on a single crystal of CaFe2As2 allowed us to establish a fairly complete picture of phonon dispersions in the main symmetry directions. The phonon spectra were also calculated…
By recognizing the vital importance of two-hole Cooper pairs (CPs) in addition to the usual two-electron ones in a strongly-interacting many-electron system, the concept of CPs was re-examined with striking conclusions. Based on this,…
Hydrogen-based compounds have attracted significant attention in recent years due to the discovery of conventional superconductivity with high critical temperature under high pressure, rekindling hopes for searching room temperature…
The partial density of vibrational states has been measured for Fe in compressed FeO (w\"ustite) using nuclear resonant inelastic x-ray scattering. Substantial changes have been observed in the overall shape of the density of states close…
Fundamental physical constants govern key effects in high-energy particle physics and astrophysics, including the stability of particles, nuclear reactions, formation and evolution of stars, synthesis of heavy nuclei and emergence of stable…