Quantum Criticality in Twisted Transition Metal Dichalcogenides

TL;DR

This study investigates the quantum critical behavior in twisted WSe₂ moiré heterostructures, revealing continuous metal-insulator transitions, strange metal behavior, and quantum fluctuations, establishing a new platform for quantum phase transition research.

Contribution

It provides the first detailed transport characterization of quantum criticality in twisted WSe₂, demonstrating continuous transitions and strange metal behavior near the metal-insulator boundary.

Findings

Metal-insulator transition is continuous as a function of density and displacement field.

Resistivity shows strange metal behavior at the transition boundary.

Fermi-liquid behavior re-emerges deep in the metallic phase.

Abstract

In moir\'e heterostructures, gate-tunable insulating phases driven by electronic correlations have been recently discovered. Here, we use transport measurements to characterize the gate-driven metal-insulator transitions and the metallic phase in twisted WSe$_2$ near half filling of the first moir\'e subband. We find that the metal-insulator transition as a function of both density and displacement field is continuous. At the metal-insulator boundary, the resistivity displays strange metal behaviour at low temperature with dissipation comparable to the Planckian limit. Further into the metallic phase, Fermi-liquid behaviour is recovered at low temperature which 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 WSe$_2$ as a new platform to study doping and bandwidth controlled metal-insulator quantum phase transitions on the triangular lattice.