Related papers: Soft phonon modes in rutile TiO$_2$
Small polaron formation in transition metal oxides, like the prototypical material rutile TiO$_2$, remains a puzzle and a challenge to simple theoretical treatment. In our combined experimental and theoretical study, we examine this problem…
The phonon renormalization across the semiconductor-to-metal crossover in FeSi is investigated by inelastic neutron scattering combined with \textit{ab-initio} lattice dynamical calculations. A significant part of reciprocal space with a…
We have carried out temperature-dependent x-ray diffraction and Raman scattering experiments on powder $Cs_3Bi_2Br_9$. Trigonal to monoclinic structural transition at around 95 K is discussed and shown to be driven by the softening of the…
We present evidence for a concomitant structural and ferroelectric transformation around $T_S\sim 360$ K in multiferroic BiFeO$_3$/LaAlO$_3$ thin films close to the tetragonal phase. Phonon excitations are investigated by using Raman…
Neutron inelastic scattering measurements of the polar TO phonon mode dispersion in the cubic relaxor Pb(Zn_1/3Nb_2/3)_0.92Ti_0.08O_3 at 500K reveal anomalous behavior in which the optic branch appears to drop precipitously into the…
Phonon dispersion of detwinned NiO is measured using inelastic x-ray scattering. It is found that, near the zone center, the energy of the transverse optical phonon mode polarized parallel to the antiferromagnetic order is ~1 meV lower than…
Recent THz spectroscopy of the quantum paraelectric SrTiO$_3$ (arXiv:2501.15771) and a high-$T_c$ cuprate (arXiv:2503.15646) has renewed interest in energy relaxation in correlated electron systems. We consider a situation in which…
Anomalous thermal expansion behaviour of several open frame-work compounds has been extensively investigated using the techniques of inelastic neutron scattering and lattice dynamics. These compounds involve increasing level of structural…
We have performed extensive ab initio calculations to investigate phonon dynamics and their possible role in superconductivity in BaFe2As2 and related systems. The calculations are compared to inelastic neutron scattering data that offer…
We investigate lattice dynamics in LaCoO$_3$ using inelastic neutron and x-ray scattering over $T = 2\mbox{-}650\,\mathrm{K}$, spanning the spin-state crossover at $T_{1} \approx 100\,\mathrm{K}$ and the insulator--metal transition at…
An infrared study of the phonon spectra of ZrW2O8 as a function of temperature which includes the low energy (2-10 meV) region relevant to negative thermal expansion is reported and discussed in the context of specific heat and neutron…
Magnetic spinels (with chemical formula $AX_{2}$O$_{4}$, with $X$ a 3$d$ transition metal ion) that also have an orbital degeneracy are Jahn-Teller active and hence possess a coupling between spin and lattice degrees of freedom. At high…
The interplay of electronic and structural degrees of freedom is a prominent feature of many quantum materials and of particular interest in systems with strong ferroelectric fluctuations, such as SrTiO$_3$ (STO) and KTaO$_3$ (KTO). Both…
Lithium transition metal phospho-olivines are useful electrode materials, owing to their stability, high safety, low cost and cyclability. We report phonon studies using neutron inelastic scattering experiments, ab-initio density functional…
Ta$_2$NiSe$_5$ became one of the most investigated candidate materials for hosting an excitonic insulator ground state. Many studies describe the corresponding phase transition as a condensation of excitons breaking a continuous symmetry.…
Raman spectroscopy experiments on single crystals of CuSb2O6 and CoSb2O6 quasi-one-dimensional antiferromagnets with trirutile crystal structure were performed, with a focus on the first material. The observed Raman-active phonon modes and…
We report lattice dynamical measurements, made using neutron inelastic scattering methods, of the relaxor perovskite PbMg1/3Nb2/3O3 (PMN) at momentum transfers near the edge of the Brillouin zone. Unusual"columns" of phonon scattering that…
Model materials are precious test cases for elementary theories and provide building blocks for the understanding of more complex cases. Here, we describe the lattice dynamics of the structural phase transition in francisite…
We have studied the S=1/2 quasi-one-dimensional antiferromagnet TiOCl using single crystal x-ray diffraction and inelastic x-ray scattering techniques. The Ti ions form staggered spin chains which dimerize below Tc1 = 66 K and have an…
The phonon dispersion was measured at room temperature along (0,0,L) in the tetragonal phase of LaFeAsO using inelastic x-ray scattering. Spin-polarized first-principles calculations imposing various types of antiferromagnetic order are in…