Related papers: Soft and Isotropic Phonons in PrFeAsO_{1-y}
Polarized Raman-scattering spectra of non-superconducting, single-crystalline FeTe are investigated as function of temperature. We have found a relation between the magnitude of ordered magnetic moments and the linewidth of A1g phonons at…
Phonon densities of states (DOS) of bcc $\alpha$-$^{57}$Fe were measured from room temperature through the 1044K Curie transition and the 1185K fcc $\gamma$-Fe phase transition using nuclear resonant inelastic x-ray scattering. At higher…
We report plane-polarized Raman scattering spectra of iron oxypnictide superconductor NdFeAsO$_{1-x}$F$_x$ single crystals with varying fluorine $x$ content. The spectra exhibit sharp and symmetrical phonon lines with a weak dependence on…
We measured phonon dispersion in single crystal EuTiO$_3$ using inelastic x-ray scattering. A structural transition to an antiferrodistortive phase was found at a critical temperature $T_0$=287$\pm$1 K using powder and single-crystal x-ray…
We carry out first-principles density-functional calculations of the antiferrodistortive (AFD) and ferroelectric (FE) soft-mode instabilities in tetragonal SrTiO3, with the structural degrees of freedom treated in a classical,…
Nematic order is ubiquitous in liquid crystals and is characterized by a rotational symmetry breaking in an otherwise uniform liquid. Recently a similar phenomenon has been observed in some electronic phases of quantum materials related to…
The intermediate valence (IV) compound YbAl$_3$ exhibits nonintegral valence (Yb 4$f^{14-n_f}$ (5d6s)$^z$ where z = 2+n$_f$ = 2.75) in a moderately heavy (m* = 20-30me) ground state with a large Kondo temperature (T$_K$ ~ 500-600K). We have…
PbTe crystals have a soft transverse optical phonon mode in the terahertz frequency range, which is known to efficiently decay into heat-carrying acoustic phonons, resulting in anomalously low thermal conductivity. Here, we studied this…
We have observed a softening of phonons and a structural phase transition in a superconducting Ba0.59K0.41BiO3 (Tc = 31 K) single crystal using elastic and inelastic neutron scattering measurements. The soft phonon occurs for the [111]…
The low-temperature antiferromagnetic state of the Sm-ions in both nonsuperconducting SmFeAsO and superconducting SmFeAsO$_{0.9}$F$_{0.1}$ single crystals was studied by magnetic torque, magnetization, and magnetoresistance measurements in…
Magnetic and crystallographic transitions in the Cairo pentagonal magnet Bi2Fe4O9 are investigated by means of infrared synchrotron-based spectroscopy as a function of temperature (20 - 300 K) and pressure (0 - 15.5 GPa). One of the phonon…
Although low-dimensional $S = 1$ antiferromagnets remain of great interest, difficulty in obtaining high-quality single crystals of the newest materials hinders experimental research in this area. Polycrystalline samples are more readily…
Fe$_{1.057(7)}$Te undergoes a first-order tetragonal to monoclinc structural transition at T$_{S} \sim 70$ K, breaking the C$_{4}$ lattice symmetry and simultaneously breaking time reversal symmetry with bicollinear magnetic order. We…
We present the results of inelastic x-ray scattering for magnetite and analyze the energies and spectral widths of the phonon modes with different symmetries in a broad range of temperature 125<T<293 K. The phonon modes with X_4 and Delta_5…
The sequence of phase transitions in PbHf0.83Sn0.17O3 has been studied by THz, far infrared and Raman spectroscopies, revealing the complementary behaviour of both, polar and non-polar phonons and their impact on the transition lattice…
We report measurements of the temperature dependence of phonon densities of states in K0.8Fe1.6Se2 using inelastic neutron scattering technique. While cooling down to 150 K, a phonon peak splitting around 25 meV is observed and a new peak…
We report here first extensive measurements of the temperature dependence of phonon density of states of BaFe2As2, the parent compound of the newly discovered FeAs-based superconductors, using inelastic neutron scattering. The experiments…
We present a detailed temperature dependent Raman light scattering study of optical phonons in Ba{1-x}K{x}Fe{2}As{2} (x ~ 0.28, superconducting Tc ~ 29 K), Sr{1-x}K{x}Fe{2}As{2} (x ~ 0.15, Tc ~ 29 K) and non-superconducting BaFe{2}As{2}…
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…
We measured phonon frequencies and linewidths in doped and undoped BaFe2As2 single crystals by inelastic x-ray scattering and compared our results with density functional theory (DFT) calculations. In agreement with previous work, the…