A5053516539- Multiferroics and related materials
- Advanced Thermoelectric Materials and Devices
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Chalcogenide Semiconductor Thin Films
- Solid-state spectroscopy and crystallography
- Ferroelectric and Piezoelectric Materials
- Thermal properties of materials
- Thermal Expansion and Ionic Conductivity
- Machine Learning in Materials Science
- Ultrasonics and Acoustic Wave Propagation
- Inorganic Chemistry and Materials
- Organic and Molecular Conductors Research
- Physics of Superconductivity and Magnetism
- Semiconductor Quantum Structures and Devices
- Iron-based superconductors research
- 2D Materials and Applications
- Heusler alloys: electronic and magnetic properties
- High-pressure geophysics and materials
- Acoustic Wave Phenomena Research
- Acoustic Wave Resonator Technologies
- Nuclear Physics and Applications
- Rare-earth and actinide compounds
- Numerical methods in engineering
- Structural Health Monitoring Techniques
Indian Institute of Technology Bombay
2020-2025
Duke University
2017-2023
Oak Ridge National Laboratory
2015-2018
Oak Ridge Associated Universities
2018
Virginia Tech
2017
Physical Sciences (United States)
2015
University at Buffalo, State University of New York
2014
Ionic conductivity and stability of Li-ion conductors are rationalized on the same footing using lattice-dynamics descriptors.
The anharmonic phonon properties of SnSe in the $Pnma$ phase were investigated with a combination experiments and first-principles simulations. Using inelastic neutron scattering (INS) nuclear resonant X-ray (NRIXS), we have measured dispersions density states (DOS) their temperature dependence, which revealed strong, inhomogeneous shift broadening spectrum on warming. First-principles simulations performed to rationalize these measurements, explain previously reported anisotropic thermal...
Intrinsically low lattice thermal conductivity ([Formula: see text]) in superionic conductors is of great interest for energy conversion applications thermoelectrics. Yet, the complex atomic dynamics leading to superionicity and ultralow remain poorly understood. Here, we report a comprehensive study diffusion [Formula: text] from energy- momentum-resolved neutron X-ray scattering techniques, combined with first-principles calculations. Our results settle unresolved questions about...
Abstract The quest for advanced superionic materials requires understanding their complex atomic dynamics, but detailed studies of the interplay between lattice vibrations and ionic diffusion remain scarce. Here inelastic quasielastic neutron scattering measurements in argyrodite Cu 7 PSe 6 are reported, combined with molecular dynamics (MD) based on ab initio machine‐learned potentials, providing critical insights into atomistic mechanisms underlying fast ion conduction. results reveal how...
Abstract The lattice dynamics and high-temperature structural transition in SnS SnSe are investigated via inelastic neutron scattering, high-resolution Raman spectroscopy anharmonic first-principles simulations. We uncover a spectacular, extreme softening reconstruction of an entire manifold low-energy acoustic optic branches across transition, reflecting strong directionality bonding strength anharmonicity. Further, our results solve prior controversy by revealing the soft-mode mechanism...
Pronounced anomalies in the SrTiO_{3} dynamical structure factor, S(Q,E), including disappearance of acoustic phonon branches at low temperatures, were uncovered with inelastic neutron scattering (INS) and simulations. The striking effect reflects anharmonic couplings between optic phonons incipient ferroelectric instability near quantum critical point. It is rationalized using a first-principles renormalized approach, pointing to nonlinear Ti-O hybridization causing unusual changes...
Magnetic frustrations and degeneracies profoundly affect ground-state magnetic properties emerging from competing exchange interactions. Controlling such using orbital phonon engineering via the Kugel-Khomskii-type (KK-type) interactions has recently enabled enhancement of magnetoelectric (ME) coupling. Using combined spectroscopic techniques first-principle simulations, here we demonstrate that magnetically frustrated Cairo lattice, Bi2Fe4O9, exhibits a strong KK-type interaction resulting...
Magnetoelectrics offer tantalizing opportunities for devices coupling ferroelectricity and magnetism but remain difficult to realize. Breakthrough strategies could circumvent the mutually exclusive origins of by exploiting interaction multiple phonon modes in geometric improper hybrid ferroelectrics. Yet, proposed instability a zone-boundary mode, driving emergence via polar remains be directly observed. Here, we provide previously missing evidence this scenario archetypal ferroelectric,...
There is growing interest in using ultrafast light pulses to drive functional materials into nonequilibrium states with novel properties. The conventional wisdom that above-gap photoexcitation behaves similarly raising the electronic temperature and lacks desired selectivity final state. Here, we report a nonthermal lattice instability induced by excitation SnSe, representative of IV−VI class semiconductors provides rich platform for tuning material functionality due their multiple...
Coupling of orbital degree freedom with a spin exchange, i.e., Kugel-Khomskii-type interaction (KK), governs host material properties, including colossal magnetoresistance, enhanced magnetoelectric response, and photoinduced high-temperature magnetism. In general, KK-type interactions lead to deviation in experimental observables coupled Hamiltonian near or below the magnetic transition. Using diffraction spectroscopy experiments, here we report anomalous changes lattice parameters,...
Strongly anharmonic phonon properties of CuCl are investigated with inelastic neutron-scattering measurements and first-principles simulations. An unusual quasiparticle spectral peak emerges in the density states increasing temperature, both simulations measurements, emanating from exceptionally strong coupling between conventional modes. Associated this anharmonicity, lattice thermal conductivity is extremely low exhibits anomalous, nonmonotonic pressure dependence. We show how behavior...
Inelastic neutron and x-ray scattering measurements of phonons spin waves were performed in the delafossite compound ${\mathrm{CuCrO}}_{2}$ over a wide range temperature, complemented with first-principles lattice dynamics simulations. The phonon dispersions density states are well reproduced by our functional calculations, reveal strong anisotropy Cu vibrations, which exhibit low-frequency modes large amplitude parallel to basal plane layered structure. low frequency in-plane also show...
Neutron and x-ray scattering measurements were performed on $(\mathrm{N}{\mathrm{a}}_{1/2}\mathrm{B}{\mathrm{i}}_{1/2})\mathrm{Ti}{\mathrm{O}}_{3}\text{\ensuremath{-}}x\phantom{\rule{0.28em}{0ex}}\mathrm{at}%\mathrm{BaTi}{\mathrm{O}}_{3}$ (NBT-$x\mathrm{BT}$) single crystals ($x=4$, 5, 6.5, 7.5) across the morphotropic phase boundary (MPB), as a function of both composition temperature, probing structural dynamical aspects. In addition to known diffuse pattern near...
Phonon properties of ${\mathrm{Mo}}_{3}{\mathrm{Sb}}_{7\ensuremath{-}x}{\mathrm{Te}}_{x}$ $(x=0,1.5,1.7)$, a potential high-temperature thermoelectric material, have been studied with inelastic neutron and x-ray scattering, first-principles simulations. The substitution Te for Sb leads to pronounced changes in the electronic structure, local bonding, phonon density states, dispersions, lifetimes. Alloying tellurium shifts Fermi level upward, near top valence band, resulting strong...
Charge density wave (CDW) induces periodic spatial modulation of the charge that is commensurate or incommensurate with host lattice periodicity, and leads to partial complete electronic band-gap opening at Fermi level (${E}_{\mathrm{F}}$). The recent finding unconventional hysteresis within CDW phase ${\mathrm{EuTe}}_{4}$, not observable in other rare-earth tellurides $R{\mathrm{Te}}_{n}$ ($n=2$, 3), has highlighted role relative distortion weakly coupled Te layers. However, detailed...
Intriguing lattice dynamics has been predicted for aperiodic crystals that contain incommensurate substructures. Here we report inelastic neutron scattering measurements of phonon and magnon dispersions in Sr14Cu24O41, which contains one-dimensional (1D) chain two-dimensional (2D) ladder Two distinct pseudoacoustic modes, corresponding to the sliding motion one sublattice against other, are observed atomic motions polarized along axis. In long wavelength limit, it is found mode shows a...
The topology of the Fermi surface controls electronic response a metal, including charge density wave (CDW) formation. A conducive for nesting (FSN) allows susceptibility ${\ensuremath{\chi}}_{0}$ to diverge and induce CDW at vector ${\mathbf{q}}_{\mathrm{CDW}}$. Kohn extended implications FSN show that imaginary part lattice dynamical ${\ensuremath{\chi}}_{L}^{\ensuremath{'}\ensuremath{'}}$ also responds anomalously all phonon branches ${\mathbf{q}}_{\mathrm{CDW}}$---a phenomenon referred...