Continuous Mott transition in semiconductor moire superlattices

The evolution of a Landau Fermi liquid into a non-magnetic Mott insulator with increasing electronic interactions is one of the most puzzling quantum phase transitions in physics(1-6). The vicinity of the transition is believed to host exotic states of matter such as quantum spin liquids(4-7), exciton condensates(8) and unconventional superconductivity(1). Semiconductor moire materials realize a highly controllable Hubbard model simulator on a triangular lattice(9-22), providing a unique opportunity to drive a metal-insulator transition (MIT) via continuous tuning of the electronic interactions. Here, by electrically tuning the effective interaction strength in MoTe2/WSe2 moire superlattices, we observe a continuous MIT at a fixed filling of one electron per unit cell. The existence of quantum criticality is supported by the scaling collapse of the resistance, a continuously vanishing charge gap as the critical point is approached from the insulating side, and a diverging quasiparticle effective mass from the metallic side. We also observe a smooth evolution of the magnetic susceptibility across the MIT and no evidence of long-range magnetic order down to similar to 5% of the Curie-Weiss temperature. This signals an abundance of low-energy spinful excitations on the insulating side that is further corroborated by the Pomeranchuk effect observed on the metallic side. Our results are consistent with the universal critical theory of a continuous Mott transition in two dimensions(4,23). The interaction strength in moire superlattices is tuned to drive a continuous metal-to-insulator transition at a fixed electron density.

Automated summary

By electrically tuning the effective interaction strength in MoTe2/WSe2 moire superlattices, a continuous metal-insulator transition is observed at a fixed filling of one electron per unit cell.