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Wei, Bin

Publications and source records attributed to Wei, Bin.

9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Temperature-dependent spin dynamics in Cr 2 O 3

Cr 2 ⁢O 3 emerges as a prominent candidate material for spintronics and magnetoelectronic applications. However, a comprehensive understanding of its temperature-dependent spin dynamics remains elusive, impeding the engineering of novel spintronics based on this material. Here, we delve into this through a combination of inelastic neutron scattering experiments and atomistic simulations. Our results unveiled the emergence of paramagnons above and below 𝑇 𝑁 . We demonstrated a significant softening of linear magnons upon heating in the antiferromagnetic state. Further analysis revealed that this softening primarily originated from four-magnon interactions, while thermal expansion played a minor role.

antiferromagnetism↗
DOE OSTI2022

Monolayer-like lattice dynamics in bulk WSe 2

Understanding the microscopic lattice dynamics is essential for regulating the thermal properties in two-dimensional layered materials. In transition metal dichalcogenides, the layered structures result in different but closely related phonon dispersions between monolayer and bulk. Here, by combining inelastic X-ray scattering and first-principles calculations, the lattice dynamics of tungsten diselenide (WSe 2 ) was investigated comprehensively, and a monolayer-like lattice dynamics in the bulk WSe 2 was revealed. We performed the first temperature-dependent phonon dispersions measurement and obtained the mode Grüneisen parameters of bulk WSe 2 , which are found to be in better agreement with the calculations on the monolayer system than those of the bulk. This observation indicates that lattice dynamics in bulk WSe 2 hold the characteristic of monolayers. The result provides valuable insights into the thermal properties of WSe 2 -based devices.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Mutual spin-phonon driving effects and phonon eigenvector renormalization in nickel (II) oxide

The physics of mutual interaction of phonon quasiparticles with electronic spin degrees of freedom, leading to unusual transport phenomena of spin and heat, has been a subject of continuing interests for decades. Despite its pivotal role in transport processes, the effect of spin-phonon coupling on the phonon system, especially acoustic phonon properties, has so far been elusive. By means of inelastic neutron scattering and first-principles calculations, anomalous scattering spectral intensity from acoustic phonons was identified in the exemplary collinear antiferromagnetic nickel (II) oxide, unveiling strong spin-lattice correlations that renormalize the polarization of acoustic phonon. In particular, a clear magnetic scattering signature of the measured neutron scattering intensity from acoustic phonons is demonstrated by its momentum transfer and temperature dependences. The anomalous scattering intensity is successfully modeled with a modified magneto-vibrational scattering cross-section, suggesting the presence of spin precession driven by phonon. The renormalization of phonon eigenvector is indicated by the observed “geometry-forbidden” neutron scattering intensity from transverse acoustic phonon. Importantly, the eigenvector renormalization cannot be explained by magnetostriction but instead, it could result from the coupling between phonon and local magnetization of ions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Giant anisotropic in-plane thermal conduction induced by Anomalous phonons in pentagonal PdSe 2

In two-dimensional materials, different atomic stacking induces anisotropic atomic interactions and phonon dispersions, leading to the anisotropy of in-plane thermal transport. In this work, we report an exceptional case in layered pentagonal PdSe 2 , where the bonding, force constants, and lattice constants are nearly-equal along the in-plane crystallographic axis directions, while the thermal conductivity is surprisingly much greater along b-axis than along a-axis with a ratio up to 1.8. Such strong anisotropy is not only unexpected in in-plane uniform structured materials, but also 2 comparable to the record high in-plane anisotropic thermal conductivity in the nonuniform structured material reported to date (the ratio is ~2.0 in TiS 3 ). By combining the inelastic X-ray scattering measurement and the first-principles calculations, we attribute such high anisotropy to the low-energy phonons along a-axis, particularly their lower group velocities and “avoided-crossing” behavior. The different buckling structures between a- (zigzag-type) and b-axis (flat-type) are mainly responsible for such unique phonon dynamics properties of PdSe 2 . This finding helps to discover materials with high anisotropic in-plane thermal conductivity in uniform structures and reveals new physics of anisotropy of in-plane thermal conduction. Due to the unique features in structure and thermal transport properties, PdSe 2 may serve as a new platform for designing novel devices to route heat flow precisely at the nanoscale.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Matryoshka phonon twinning in α-GaN

Understanding lattice dynamics is crucial for effective thermal management in electronic devices because phonons dominate thermal transport in most semiconductors. α -GaN has become a focus of interest as one of the most important third-generation power semiconductors, however, the knowledge on its phonon dynamics remains limited. Here we show a Matryoshka phonon dispersion of α -GaN with the complementary inelastic X-ray and neutron scattering techniques and the first-principles calculations. Such Matryoshka twinning throughout the basal plane of the reciprocal space is demonstrated to amplify the anharmonicity of the related phonons through creating abundant three-phonon scattering channels and cutting the lifetime of affected modes by more than 50%. Such phonon topology contributes to reducing the in-plane thermal transport, thus the anisotropic thermal conductivity of α -GaN. The results not only have implications for engineering the thermal performance of α -GaN, but also offer valuable insights on the role of anomalous phonon topology in thermal transport of other technically semiconductors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Ultrathin high- κ antimony oxide single crystals

Ultrathin oxides have been reported to possess excellent properties in electronic, magnetic, optical, and catalytic fields. However, the current and primary approaches toward the preparation of ultrathin oxides are only applicable to amorphous or polycrystalline oxide nanosheets or films. Here, we successfully synthesize high-quality ultrathin antimony oxide single crystals via a substrate-buffer-controlled chemical vapor deposition strategy. The as-obtained ultrathin antimony oxide single crystals exhibit high dielectric constant (~100) and large breakdown voltage (~5.7 GVm -1 ). Such a strategy can also be utilized to fabricate other ultrathin oxides, opening up an avenue in broadening the applicaitons of ultrathin oxides in many emerging fields.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Anomalously Suppressed Thermal Conduction by Electron-Phonon Coupling in Charge-Density-Wave Tantalum Disulfide

Charge and thermal transport in a crystal is carried by free electrons and phonons (quantized lattice vibration), the two most fundamental quasiparticles. Above the Debye temperature of the crystal, phonon-mediated thermal conductivity ( κ L ) is typically limited by mutual scattering of phonons, which results in κ L decreasing with inverse temperature, whereas free electrons play a negligible role in κ L . Here, an unusual case in charge-density-wave tantalum disulfide (1T-TaS 2 ) is reported, in which κ L is limited instead by phonon scattering with free electrons, resulting in a temperature-independent κ L . In this system, the conventional phonon–phonon scattering is alleviated by its uniquely structured phonon dispersions, while unusually strong electron-phonon (e-ph) coupling arises from its Fermi surface strongly nested at wavevectors in which phonons exhibit Kohn anomalies. The unusual temperature dependence of thermal conduction is found as a consequence of these effects. The finding reveals new physics of thermal conduction, offers a unique platform to probe e-ph interactions, and provides potential ways to control heat flow in materials with free charge carriers. The temperature-independent thermal conductivity may also find thermal management application as a special thermal interface material between two systems when the heat conduction between them needs to be maintained at a constant level.

36 MATERIALS SCIENCE↗