Robust Super-Moir\'e in Large Angle Single-Twist Bilayers

TL;DR

This paper introduces a novel approach to create robust super-moiré structures in large-angle twisted bilayers, combining advantages of small and large twist angles to achieve stable, tunable flat bands for advanced quantum material applications.

Contribution

It proposes a new method to engineer super-moiré structures at large twist angles using a single near-commensurate angle, enabling stable and controllable flat bands in bilayer materials.

Findings

Spontaneous formation of periodic commensurate moiré stacking patterns.

Tunable periodicity through slight deviations from commensurate angles.

Presence of van Hove singularities indicating strong band hybridization.

Abstract

Forming long wavelength moir\'e superlattices (MSL) at small-angle twist van der Waals (vdW) bilayers has been a key approach to creating moir\'e flat bands. The small-angle twist, however, leads to strong lattice reconstruction, causing domain walls and moir\'e disorders, which pose considerable challenges in engineering such platforms. At large twist angles, the rigid lattices render a more robust, but shorter wavelength MSL, making it difficult to engineer flat bands. Here, we depict a novel approach to tailoring robust super-moir\'e (SM) structures that combines the advantages of both small-twist and large-twist transition metal dichalcogenides (TMDs) bilayers using only a single twist angle near a commensurate angle. Structurally, we unveil the spontaneous formation of a periodic arrangement of three inequivalent commensurate moir\'e (CM) stacking, where the angle deviation from the commensurate angle can tune the periodicity. Electronically, we reveal a large set of van Hove singularities (VHSs) that indicate strong band hybridization, leading to flat bands near the valence band maximum. Our study paves the way for a new platform of robust SM bilayers with structural rigidity and controllable wavelength, extending the investigation of the interplay among band topology, quantum geometry, and moir\'e superconductivity to the large twist angle regime.