Optimal superconductivity in twisted bilayer WSe$_2$ where the Van Hove singularity crosses half-filling

TL;DR

This paper investigates how displacement fields and electron interactions induce superconductivity in twisted bilayer WSe$_2$, highlighting the role of Van Hove singularities crossing half-filling and their interplay with correlation effects.

Contribution

It introduces a detailed theoretical analysis using a $t$-$J$-$U$ model to explain the emergence of superconductivity near Van Hove singularities in twisted WSe$_2$, aligning with experimental observations.

Findings

Superconductivity is stabilized near Van Hove singularity crossing half-filling.

The interplay of density of states and correlation effects creates favorable pairing conditions.

Superconducting phase exists only within a small region of the phase diagram.

Abstract

The recent discovery of unconventional superconductivity has pointed to twisted WSe$_2$ bilayer as a versatile platform for studying the correlated and topological phases of matter. Here we analyze the effect of the displacement field and electron interactions on the formation of a topological paired state in twisted WSe$_2$. Our approach is based on the effective single band $t$-$J$-$U$ model supplemented with intersite Coulomb interaction term and treated within the Gutzwiller approximation. We show that the superconducting phase is stabilized in a small range of displacement fields where the Van Hove singularity crosses half-filling, which is in qualitative agreement with recent experimental data. According to our analysis, such a circumstance comes as a result of a subtle interplay between the large density of states of the Van Hove singularity, in combination with the renormalization effects that appear in the weak-to-moderate correlations regime. The two factors create favorable conditions for the SC pairing only in a small area of the phase diagram.