arXiv subjects

Yateng Wang

Publications and source records attributed to Yateng Wang.

5 recordsLinked to original sources

arXiv2026

Polarization Rotation Drives a Spin-Topological Transition in Ferroelectric Bismuth Monolayer

Bismuth monolayer is the first two-dimensional elemental ferroelectric and an appealing platform for coupling polar order to spin-orbit-driven topology. However, its microscopic switching mechanism remains elusive. Here, using first-principles lattice dynamics and symmetry-adapted mode analysis, we identify a previously overlooked rotational pathway for in-plane polarization switching. Its energy barrier is more than four times lower than that of direct reversal, naturally explaining the vortexlike domain textures observed in molecular dynamics simulations. Remarkably, this polarization rotation also drives a spin-topological transition, changing the spin Chern number from $C_s=-2$ to $0$. Directional uniaxial strain further steers the polarization orientation and tunes the associated topological transition. These results establish polarization rotation as the switching mechanism of ferroelectric Bi monolayer and as an efficient route to electrically and mechanically programmable topology in two-dimensional ferroelectrics.

cond-mat.mtrl-sci↗

arXiv2026

Weak Polar Optical Phonon Scattering Decouples Electron and Phonon Transport in Layered Thermoelectric Materials

High-performance thermoelectric (TE) materials are crucial for efficient waste-heat recovery and solid-state cooling technologies. A persistent challenge in TE materials design arises from the strong interdependence among the electrical conductivity ($\sigma$), Seebeck coefficient ($S$), and lattice thermal conductivity ($\kappa_{\mathrm{L}}$). Layered compounds can effectively suppress $\kappa_{\mathrm{L}}$ along the cross-plane direction owing to weak interlayer interactions; however, they often suffer from low carrier mobility ($\mu$) caused by limited band dispersion and strong polar optical phonon (POP) scattering. Here, we perform high-throughput density functional theory calculations to screen 236 layered semiconductors and identify candidates with low effective mass ($m^{*}$) and weak POP scattering. We identify 23 compounds with high cross-plane $\mu$, among which 14 exhibit large power factors ($S^{2}\sigma$). Notably, GaGe$_{2}$Te stands out with exceptionally high cross-plane $\sigma$ and power factor, enabled by a favorable combination of small $m^{*}$ and a small ionic dielectric constant. Simultaneously, GaGe$_{2}$Te exhibits an ultralow cross-plane $\kappa_{\mathrm{L}}$ of 0.57~W~m$^{-1}$~K$^{-1}$ at 300~K, originating from weak interlayer bonding and pronounced phonon anharmonicity. These results demonstrate an effective strategy to decouple electron and phonon transport in layered materials by mitigating POP scattering, thereby providing a promising pathway toward high-performance thermoelectric materials.

cond-mat.mtrl-sci↗

arXiv2026

Microscopic Origin of the Ultralow Lattice Thermal Conductivity in Vacancy-Ordered Halide Double Perovskites Cs$_2BX_6$ ($B$ = Zr, Pd, Sn, Te, Hf, and Pt; $X$= Cl, Br, and I)

Vacancy-ordered halide double perovskites Cs$_2BX_6$ have recently attracted significant attention due to their intrinsically ultralow lattice thermal conductivity ($\kappa_{\mathrm{L}}$), which is highly desirable for thermal insulation and thermoelectric applications. In this work, we systematically investigate the anharmonic lattice dynamics and thermal transport properties of Cs$_2BX_6$ ($B$ = Zr, Pd, Sn, Te, Hf, and Pt; $X$ = Cl, Br, and I) using state-of-the-art first-principles calculations, based on a unified theory of thermal transport for crystals and glasses. All studied compounds are found to exhibit ultralow $\kappa_{\mathrm{L}}$ below 1.0~W\,m$^{-1}$\,K$^{-1}$ at room temperature and large derivation from the conventional $T^{-1}$ temperature dependence. Our analysis combining with machine-learning approach show that low sound velocities (1100 -- 1600~m\,s$^{-1}$), which originates from the intrinsically weak chemical bonding, play a crucial role in suppressing heat transport of the most compounds, instead of the strong scattering of rattling phonon modes expected from the large void in the structure. Furthermore, the influence of $B$ and $X$-site elements on phonon dispersion, anharmonicity, and scattering phase space is clarified. Our results provide microscopic insights into the origin of ultralow $\kappa_{\mathrm{L}}$ in Cs$_2BX_6$ and offer guiding principles for the rational design of halide-based materials with tailored thermal transport properties.

cond-mat.mtrl-sci↗

arXiv2025

Stacking effects on magnetic, vibrational, and optical properties of CrSBr bilayers

The van der Waals layered semiconductor CrSBr, which exhibits A-type antiferromagnetism and a relatively high Néel temperature, has been successfully exfoliated into atomically thin sheets. In this study, we investigate the structural, lattice dynamical, electronic, magnetic, and optical properties of four distinct stacking structures of CrSBr bilayers using first-principles calculations and Monte Carlo simulations. Our findings show that though the most energetically favorable bilayer structure retains the stacking pattern of the bulk counterpart, three other high-symmetry stacking structures can be achieved by sliding one of the layers along three distinct directions, with energy costs comparable to that observed in MoS$_2$ bilayer. All these four bilayers exhibit semiconductor behavior with A-type antiferromagnetic ordering, similar to the bulk material, and demonstrate closely aligned Néel temperatures. Moreover, these bilayers exhibit relatively low lattice thermal conductivities, pronounced anisotropy, and a strong dependence on stacking patterns. This behavior is attributed to significant phonon-phonon scattering arising from avoided crossings between acoustic and optical phonons, as well as the presence of flat optical phonon bands in the low-frequency region. While the electronic structures and optical properties of these bilayers show weak dependence on the stacking pattern for antiferromagnetic ordering, they undergo significant changes for ferromagnetic ordering, influencing the band gap, valence and conduction band splitting, and effective mass. Furthermore, we found that antiferromagnetic ordering can transition to ferromagnetic under intense visible light illumination. Thus, the integration of layer stacking and visible light illumination offers an effective means to control the heat transfer, magnetic, and optical properties of CrSBr bilayers.

cond-mat.mtrl-sci↗

arXiv2024

Thermal stabilities Landscape of A$_2$BB$^{\prime}$O$_6$ compounds

Perovskite oxides have been extensively studied for their wide range of compositions and structures, as well as their valuable properties for various applications. Expanding from single perovskite ABO$_3$ to double perovskite $A_2BB^{\prime}$O$_6$ significantly enhances the ability to tailor specific physical and chemical properties. However, the vast number of potential compositions of $A_2BB^{\prime}$O$_6$ makes it impractical to explore them all experimentally. In this study, we conducted high-throughput calculations to systematically investigate the structures and stabilities of 4,900 $A_2BB^{\prime}$O$_6$ compositions (with $A$ = Ca, Sr, Ba, and La; $B$ and $B^{\prime}$ representing metal elements) through over 42,000 density functional theory (DFT) calculations. Our analysis lead to the discovery of more than 1,500 new synthesizable $A_2BB^{\prime}$O$_6$ compounds, with over 1,100 of them exhibiting double perovskite structures, predominantly in the $P2_1/c$ space group. By leveraging the high-throughput dataset, we developed machine learning models that achieved mean absolute errors of 0.0444 and 0.0330 eV/atom for formation energy and decomposition energy, respectively. Using these models, we identified 803 stable or metastable compositions beyond the chemical space covered in our initial calculations, with 612 of them having DFT-validated decomposition energies below 0.1 eV/atom, resulting in a success rate of 76.2 \%. This study delineates the stability landscape of $A_2BB^{\prime}$O$_6$ compounds and offers new insights for the exploration of these materials.

cond-mat.mtrl-sci↗