arXiv subjects

Koichiro Kato

Publications and source records attributed to Koichiro Kato.

2 recordsLinked to original sources

arXiv2026

One-Dimensional Electronic States in a Moir\'e Superlattice of Twisted Bilayer WTe2

One-dimensional (1D) moir\'e superlattices provide a new route to engineering reduced-dimensional electronic states in van der Waals materials, yet their electronic structure and microscopic origin remain largely unexplored. Here, we investigate the structural relaxation and electronic properties of a 1D moir\'e superlattice formed in twisted bilayer 1T$'$-WTe$_2$ using density functional theory calculations, complemented by high-angle annular dark-field scanning transmission electron microscopy. We show that lattice relaxation strongly reconstructs the moir\'e stripes, leading to stacking-dependent stripe widths that are in excellent agreement with experimental observations. The relaxed structure hosts quasi-one-dimensional electronic bands near the Fermi level, characterized by strong dispersion along the stripe direction and nearly flat dispersion in the perpendicular direction. By comparing the full bilayer with isolated relaxed layers, we establish that these 1D electronic states are governed predominantly by an intralayer moir\'e potential induced by in-plane lattice relaxation, rather than by interlayer hybridization. We extract this position-dependent moir\'e potential directly from DFT calculations and construct an effective tight-binding model that reproduces both the band dispersion and the real-space localization of the electronic wave functions. Our results identify lattice relaxation as the key mechanism underlying 1D electronic states in 1D moir\'e superlattices. %and establish twisted bilayer WTe$_2$ as a promising platform for exploring emergent one-dimensional moir\'e physics. The framework developed here provides a unified theoretical basis for realizing and exploring one-dimensional moir\'e physics in a broad class of anisotropic two-dimensional materials.

cond-mat.mes-hall↗

arXiv2025

Moir\'e Band Engineering in Twisted Trilayer WSe2

We present a systematic theoretical study on the structural and electronic properties of twisted trilayer transition metal dichalcogenide (TMD) WSe$_2$, where two independent moir\'e patterns form between adjacent layers. Using a continuum approach, we investigate the optimized lattice structure and the resulting energy band structure, revealing fundamentally different electronic behaviors between helical and alternating twist configurations. In helical trilayers, lattice relaxation induces $\alpha\beta$ and $\beta\alpha$ domains, where the two moir\'e patterns shift to minimize overlap, while in alternating trilayers, $\alpha\alpha'$ domains emerge with aligned moir\'e patterns. A key feature of trilayer TMDs is the summation of moir\'e potentials from the top and bottom layers onto the middle layer, effectively doubling the potential depth. In helical trilayers, this mechanism generates a Kagome lattice potential in the $\alpha\beta$ domains, giving rise to flat bands characteristic of Kagome physics. In alternating trilayers, the enhanced potential confinement forms deep triangular quantum wells, distinct from those found in bilayer systems. Furthermore, we demonstrate that a moderate perpendicular electric field can switch the layer polarization near the valence band edge, providing an additional degree of tunability. In particular, it enables tuning of the hybridization between orbitals on different layers, allowing for the engineering of diverse and controllable electronic band structures. Our findings highlight the unique role of moir\'e potential summation in trilayer systems, offering a broader platform for designing moir\'e-based electronic and excitonic phenomena beyond those achievable in bilayer TMDs.

cond-mat.mes-hall↗