Emergent magnetism and spin liquids in an extended Hubbard description of moir\'e bilayers

TL;DR

This paper investigates an extended Hubbard model inspired by twisted TMDs, revealing emergent magnetic states including quantum spin liquids due to charge order and strong interactions.

Contribution

It introduces a detailed study of charge and magnetic order in moiré bilayers using large-scale DMRG, highlighting the emergence of quantum spin liquids.

Findings

Charge order at fractional fillings in extended Hubbard model

Existence of quantum spin liquid states on Kagomé-like charge order

Dependence of magnetic states on interaction parameters

Abstract

Motivated by twisted transition metal dichalcogenides (TMDs), we study an extended Hubbard model with both on-site and off-site repulsive interactions, in which Mott insulating states with concomitant charge order occur at fractional fillings. To resolve the charge ordering as well as the fate of the local moments formed thereby, we perform large-scale density matrix renormalization group calculations on cylindrical geometries for several filling fractions and ranges of interaction strength. Depending on the precise parameter regime, both antiferromagnetically ordered as well as quantum-disordered states are found, with a particularly prominent example being a quantum spin liquid-type ground state on top of charge-ordering with effective Kagom\'e geometry. We discuss the different mechanisms at play in stabilizing various electronic and magnetic states. The results suggest that moir\'e TMDs are a promising venue for emergent quantum magnetism of strongly interacting electrons.