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Creators/Authors contains: "Xiao, Di"

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  1. Abstract Motivated by recent experimental observations of opposite Chern numbers in R-type twisted MoTe2and WSe2homobilayers, we perform large-scale density-functional-theory calculations with machine learning force fields to investigate moiré band topology across a range of twist angles in both materials. We find that the Chern numbers of the moiré frontier bands change sign as a function of twist angle, and this change is driven by the competition between moiré ferroelectricity and piezoelectricity. Our large-scale calculations, enabled by machine learning methods, reveal crucial insights into interactions across different scales in twisted bilayer systems. The interplay between atomic-level relaxation effects and moiré-scale electrostatic potential variation opens new avenues for the design of intertwined topological and correlated states, including the possibility of mimicking higher Landau level physics in the absence of magnetic field. 
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    Free, publicly-accessible full text available December 1, 2025
  2. Abstract Noncollinear ferroic materials are sought after as testbeds to explore the intimate connections between topology and symmetry, which result in electronic, optical, and magnetic functionalities not observed in collinear ferroic materials. For example, ferroaxial materials have rotational structural distortions that break mirror symmetry and induce chirality. When ferroaxial order is coupled with ferroelectricity arising from a broken inversion symmetry, it offers the prospect of electric‐field‐control of the ferroaxial distortions and opens up new tunable functionalities. However, chiral multiferroics, especially ones stable at room temperature, are rare. A strain‐stabilized, room‐temperature chiral multiferroic phase in single crystals of BaTiS3is reported here. Using first‐principles calculations, the stabilization of this multiferroic phase havingP63space group for biaxial tensile strains exceeding 1.5% applied on the basalab‐plane of the room temperatureP63cmphase of BaTiS3is predicted. The chiral multiferroic phase is characterized by rotational distortions of TiS6octahedra around the longc‐axis and polar displacement of Ti atoms along thec‐axis. The ferroaxial and ferroelectric distortions and their domains inP63‐BaTiS3are directly resolved using atomic resolution scanning transmission electron microscopy. Landau‐based phenomenological modeling predicts a strong coupling between the ferroelectric and the ferroaxial order makingP63‐BaTiS3an attractive test bed for achieving electric‐field‐control of chirality. 
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    Free, publicly-accessible full text available March 1, 2026
  3. Free, publicly-accessible full text available December 1, 2025
  4. Free, publicly-accessible full text available March 20, 2026
  5. Free, publicly-accessible full text available November 21, 2025