A tunable bilayer Hubbard model in twisted WSe2

Twisted WSe2 AB-homobilayers enable the realization of bilayer Hubbard models in the weak interlayer hopping limit. Moire materials with flat electronic bands provide a highly controllable quantum system for studies of strong-correlation physics and topology. In particular, angle-aligned heterobilayers of semiconducting transition metal dichalcogenides with large band offset realize the single-band Hubbard model. Introduction of a new layer degree of freedom is expected to foster richer interactions, enabling Hund's physics, interlayer exciton condensation and new superconducting pairing mechanisms to name a few. Here we report competing electronic states in twisted AB-homobilayer WSe2, which realizes a bilayer Hubbard model in the weak interlayer hopping limit for holes. By layer-polarizing holes via a perpendicular electric field, we observe a crossover from an excitonic insulator to a charge-transfer insulator at a hole density of nu = 1 (in units of moire density), a transition from a paramagnetic to an antiferromagnetic charge-transfer insulator at nu = 2 and evidence for a layer-selective Mott insulator at 1 < nu < 2. The unique coupling of charge and spin to external electric and magnetic fields also manifests a giant magnetoelectric response. Our results establish a new solid-state simulator for the bilayer Hubbard model Hamiltonian.

Automated summary

Twisting the AB-homobilayer of WSe2 enables the realization of bilayer Hubbard model in the weak interlayer hopping limit, leading to observation of competing electronic states transition.