Realization of nearly dispersionless bands with strong orbital anisotropy from destructive interference in twisted bilayer MoS2

Lede Xian,Simon Trebst,Dominik Kiese,Dante M Kennes,Angel Rubio,Michael M Scherer,Martin Claassen

doi:10.1038/s41467-021-25922-8

Abstract

Recently, the twist angle between adjacent sheets of stacked van der Waals materials emerged as a new knob to engineer correlated states of matter in two-dimensional heterostructures in a controlled manner, giving rise to emergent phenomena such as superconductivity or correlated insulating states. Here, we use an ab initio based approach to characterize the electronic properties of twisted bilayer MoS2. We report that, in marked contrast to twisted bilayer graphene, slightly hole-doped MoS2 realizes a strongly asymmetric px-py Hubbard model on the honeycomb lattice, with two almost entirely dispersionless bands emerging due to destructive interference. The origin of these dispersionless bands, is similar to that of the flat bands in the prototypical Lieb or Kagome lattices and co-exists with the general band flattening at small twist angle due to the moiré interference. We study the collective behavior of twisted bilayer MoS2 in the presence of interactions, and characterize an array of different magnetic and orbitally-ordered correlated phases, which may be susceptible to quantum fluctuations giving rise to exotic, purely quantum, states of matter.

Highlights

The twist angle between adjacent sheets of stacked van der Waals materials emerged as a new knob to engineer correlated states of matter in two-dimensional heterostructures in a controlled manner, giving rise to emergent phenomena such as superconductivity or correlated insulating states
Linear combinations of the macroscopically degenerate extended Bloch states in these systems allows to form localized Wannier-like eigenstates with no dispersion. Such flat band systems can give rise to many interesting phenomena, such as the formation of nontrivial topology when time-reversal symmetry is broken, or other exotic quantum phases of matter due to their susceptibility to quantum fluctuations and electronic correlations[32]. We demonstrate that both flat band mechanisms can be engineered to coexist in twisted bilayers of MoS2: a transition metal dichalcogenides (TMDs) of direct experimental relevance that has been extensively studied from synthesis to applications[33,34]
While for twisted bilayer graphene this effect is only significant at twist angles smaller than 1 degree[54], it noticeably alters the low-energy band dispersions and charges density localization for twisted transition metal dichalcogenides bilayer even with relatively large twist angles above 1 degree[12,35]

Summary

Introduction

The twist angle between adjacent sheets of stacked van der Waals materials emerged as a new knob to engineer correlated states of matter in two-dimensional heterostructures in a controlled manner, giving rise to emergent phenomena such as superconductivity or correlated insulating states. Purely geometric considerations lead to the formation of perfectly localized electronic states that have weight only on single plaquettes or hexagons, respectively, and that are eigenstates of the kinetic Hamiltonian due to destructive interference between lattice hopping matrix elements[31] To put it differently, linear combinations of the macroscopically degenerate extended Bloch states in these systems allows to form localized Wannier-like eigenstates (living on single plaquettes or hexagons in the examples above) with no dispersion (for a review on the subject see, e.g,32). Linear combinations of the macroscopically degenerate extended Bloch states in these systems allows to form localized Wannier-like eigenstates (living on single plaquettes or hexagons in the examples above) with no dispersion (for a review on the subject see, e.g,32) Such flat band systems can give rise to many interesting phenomena, such as the formation of nontrivial topology when time-reversal symmetry is broken, or other exotic quantum phases of matter due to their susceptibility to quantum fluctuations and electronic correlations[32]

Methods

Results

Conclusion