Approximate symmetries, insulators, and superconductivity in continuum-model description of twisted WSe$_2$

TL;DR

This paper investigates the correlated electronic phases, including insulators and superconductivity, in twisted bilayer WSe$_2$ using a continuum model, symmetry analysis, and studying various pairing mechanisms.

Contribution

It introduces a continuum model analysis of twisted WSe$_2$, classifies potential superconducting states, and links them to nearby insulating phases, considering effects of perturbations and electron-phonon coupling.

Findings

Identification of strong-coupling ground states.

Superconductivity linked to intervalley coherent phases.

Possible nodal, chiral, or fully gapped pairing states.

Abstract

Motivated by the recent discovery of superconductivity in twisted bilayer WSe$_2$, we analyze the correlated physics in this system in the framework of a continuum model for the moir\'e superlattice. Using the symmetries in a fine-tuned limit of the system, we identify the strong-coupling ground states and their fate when the perturbations caused by finite bandwidth, displacement field, and the phase of the intralayer potential are taken into account. We classify the superconducting instabilities and, employing a spin-fermion-like model, study the superconducting instabilities in proximity to these insulating particle-hole orders. This reveals that only a neighboring intervalley coherent phase (with zero or finite wave vector) is naturally consistent with the observed superconducting state. Depending on details, the superconductor will be nodal or a chiral gapped state while further including electron-phonon coupling leads to a fully gapped, time-reversal symmetric pairing state.