Theory of tunable flux lattices in the homobilayer moir\'e of twisted and uniformly strained transition metal dichalcogenides

TL;DR

This paper develops a geometric theory for moiré structures in twisted and strained homobilayer transition metal dichalcogenides, revealing how strain and bias can tune emergent magnetic fields and scalar potentials for topological applications.

Contribution

It introduces a geometric framework to understand and control moiré magnetic fields and scalar potentials in TMD homobilayers, highlighting strain and bias as tuning parameters.

Findings

Moiré structures exhibit vortex/antivortex pseudo-spin textures.

Strain and bias can be used to engineer the moiré magnetic field.

Scalar potentials can be tailored to create effective lattice structures.

Abstract

The spatial texture of internal degree of freedom of electrons has profound effects on the properties of materials. Such texture in real space can manifest as an emergent magnetic field (or Berry curvature), which is expected to induce interesting valley/spin-related transport phenomena. Moir\'e pattern, which emerges as a spatial variation at the interface of 2D atomic crystals, provides a natural platform for investigating such real space Berry curvature effects. Here we study moir\'e structures formed in homobilayer transition metal dichalcogenides (TMDs) due to twisting, various uniform strain profiles, and their combinations, where electrons can reside in either layer with the layer index serving as an internal degree of freedom. The layer pseudo-spin exhibits vortex/antivortex textures in the moir\'e supercell, leading to a giant geometric magnetic field and a scalar potential. Within a geometric picture, the moir\'e magnetic field is found as the cross product of the gradients of the out-of-plane pseudo-spin and the in-plane pseudo-spin orientation respectively. We discover dual roles of uniform strain: Besides being a cause of the moire atomic texture in the homobilayer, it also contributes a pseudo-gauge potential that modifies the local phase of interlayer coupling. Consequently, strain can be employed to tune the in-plane pseudo-spin texture, while interlayer bias tunes the out-of-plane pseudo-spin, and we show how the moir\'e magnetic field's spatial profile, intensity, and flux per supercell can be engineered. Through the geometric scalar correction, the landscape of the scalar potential can also be engineered along with the moir\'e magnetic field, forming distinct effective lattice structures. These properties render TMD moir\'e structures promising to build tunable flux lattices for transport and topological material applications.