Quantum criticality in twisted transition metal dichalcogenides

Abstract

Near the boundary between ordered and disordered quantum phases, several experiments have demonstrated metallic behaviour that defies the Landau Fermi paradigm^1-5. In moiré heterostructures, gate-tuneable insulating phases driven by electronic correlations have been recently discovered^6-23. Here, we use transport measurements to characterize metal-insulator transitions (MITs) in twisted WSe₂ near half filling of the first moiré subband. We find that the MIT as a function of both density and displacement field is continuous. At the metal-insulator boundary, the resistivity displays strange metal behaviour at low temperatures, with dissipation comparable to that at the Planckian limit. Further into the metallic phase, Fermi liquid behaviour is recovered at low temperature, and this evolves into a quantum critical fan at intermediate temperatures, before eventually reaching an anomalous saturated regime near room temperature. An analysis of the residual resistivity indicates the presence of strong quantum fluctuations in the insulating phase. These results establish twisted WSe₂ as a new platform to study doping and bandwidth-controlled metal-insulator quantum phase transitions on the triangular lattice.