A New Moir\'e Platform Based on M-Point Twisting

TL;DR

This paper introduces a novel class of moiré materials based on monolayers with M-point valleys, proposing twisted bilayers of SnSe2 and ZrS2 as experimental realizations, and explores their unique symmetries, flat bands, and potential for correlated physics.

Contribution

It presents the first experimentally feasible M-point moiré systems, develops their continuum models, and uncovers emergent non-symmorphic symmetries and kagome lattice structures in momentum space.

Findings

Identification of M-point moiré materials with unique symmetries

Prediction of flat bands at specific twist angles

Potential for realizing Luttinger liquid physics

Abstract

We introduce a new class of moir\'e systems and materials based on monolayers with triangular lattices and low-energy states at the M points of the Brillouin zone. These M-point moir\'e materials are fundamentally distinct from those derived from $\Gamma$- or K-point monolayers, featuring three time-reversal-preserving valleys related by three-fold rotational symmetry. We propose twisted bilayers of experimentally exfoliable 1T-SnSe$_2$ and 1T-ZrS$_2$ as realizations of this new class. Using extensive ab initio simulations, we develop quantitative continuum models and analytically show that the corresponding M-point moir\'e Hamiltonians exhibit emergent momentum-space non-symmorphic symmetries and a kagome plane-wave lattice in momentum space. This represents the first experimentally viable realization of a projective representation of crystalline space groups in a non-magnetic system. With interactions, these materials represent six-flavor Hubbard simulators with Mott physics, as can be seen by their flat Wilson loops. Furthermore, the presence of a non-symmorphic momentum-space in-plane mirror symmetry makes some of the M-point moir\'e Hamiltonians quasi-one-dimensional in each valley, suggesting the possibility of realizing Luttinger liquid physics. We predict the twist angles at which a series of (conduction) flat bands appear, provide a faithful continuum Hamiltonian, analyze its topology and charge density and briefly discuss several aspects of the physics of this new platform.