Spin transport of a doped Mott insulator in moiré heterostructures

Abstract

Moiré superlattices of semiconducting transition metal dichalcogenide (TMD) heterobilayers are model systems for investigating strongly correlated electronic phenomena1-12. Specifically, WSe2/WS2 moiré superlattices has emerged as a quantum simulator for the 2D extended Hubbard model1,2, which hosts fascinating correlated charge and spin physics. Experimental studies of charge transport have revealed correlated Mott insulator1,2 and generalized Wigner crystal states1, but spin transport of the moiré heterostructure has not yet been explored. Here, we use spatial- and temporal-resolved circular dichroism spectroscopy to directly image the spin transport as a function of carrier doping and temperature in WSe2/WS2 moiré heterostructures. We observe diffusive spin transport at all hole concentrations at 11 Kelvin, including the Mott insulator at one hole per moiré unit cell, where charge transport is strongly suppressed. At elevated temperatures the spin diffusion constant remains unchanged at the Mott insulator state, but it increases significantly at finite doping away from the Mott state. The doping- and temperature-dependent spin transport can be qualitatively understood using a t-J model, where spins can move via hopping of spin-carrying charges and via the exchange interaction. From the measured spin diffusion constant, we can estimate the effective hopping amplitude t and exchange coupling J in the superlattice. Our results demonstrate opportunities for exploring novel spin physics in correlated electronic systems using TMD moiré superlattices.