Charge and spin properties of a generalized Wigner crystal realized in the moir\'e WSe$_2$/WS$_2$ heterobilayer

TL;DR

This study models the charge and spin characteristics of a generalized Wigner crystal in a moiré WSe2/WS2 heterobilayer at 2/3 electron filling, revealing a transition from metal to insulator with emergent magnetic order.

Contribution

It introduces a detailed theoretical analysis of a generalized Wigner crystal in a moiré heterobilayer using an extended-Hubbard model and DMRG, highlighting new magnetic phenomena.

Findings

Transition from metallic to insulating state with increasing intersite interactions.

Formation of a honeycomb pattern Wigner crystal at 2/3 filling.

Spin canting induced by spin-valley polarization and intersite repulsion.

Abstract

We examine the charge and spin properties of an effective single-band model representing a moir\'e superlattice of the WSe$_{2}$/WS$_{2}$ heterobilayer. We focus on the $2/3$ electron filling, which refers to the formation of a generalized Wigner crystal, as evidenced experimentally. Our approach is based on the extended-Hubbard model on a triangular lattice with non-interacting part effectively describing a spin-split band due to Ising-type spin-orbit coupling. We investigate the system in the regime of strong on-site Coulomb repulsion and the ground state of the Hamiltonian is obtained with the use of the Density Matrix Renormalization Group formulated within the Matrix Product State approach. According to our analysis, based on the density-density correlation functions resolved in the momentum space, a transition from the metallic to the insulating state appears with increasing intersite electron-electron interactions. This transition is identified as being concomitant with the emergence of a generalized Wigner crystal that realizes the honeycomb lattice pattern. We investigate the magnetic properties of such a Wigner crystal state and find that the presence of spin-valley polarization and the increased intersite repulsion induce spin canting of the out-of-plane antiferromagnetic ordering.