Superconductivity in moir\'e transition metal dichalcogenide bilayers: comparison of two distinct theoretical approaches

TL;DR

This paper compares two theoretical models for superconductivity in moiré transition-metal dichalcogenide bilayers, highlighting their differences in pairing mechanisms and implications for experimental observations.

Contribution

It introduces and contrasts two distinct theoretical approaches, the negative U-Hubbard and t-J-U models, to understand superconductivity in twisted WSe2.

Findings

The negative U-Hubbard model predicts an isotropic s-wave gap unaffected by strong correlations.

The t-J-U model allows for unconventional gap symmetries influenced by Coulomb repulsion.

Comparison of models provides insights consistent with experimental data.

Abstract

Superconductivity has recently been observed in moir\'e transition-metal dichalcogenide bilayers. Here, we investigate the superconducting state in twisted WSe$_2$ using two complementary theoretical approaches. The first is based on the negative $U$-Hubbard model and represents a relatively conventional pairing scenario, in which strong electron-electron repulsion does not directly affect the paired state and an isotropic $s$-$wave$ gap emerges. The second approach employs the $t$-$J$-$U$ model, allowing for unconventional gap symmetries and incorporating strong correlation effects via substantial renormalization induced by Coulomb repulsion. We compare the key properties of the superconducting states obtained within these two frameworks and discuss their implications in light of available experimental observations.