Kohn-Luttinger Mechanism of Superconductivity in Twisted Bilayer WSe$_2$: Gate-Tunable Unconventional Pairing Symmetry

Abstract: Motivated by the recent discovery of superconductivity in twisted bilayer WSe$_2$, we theoretically investigate the pairing instability induced by Coulomb interaction via the Kohn-Luttinger mechanism. Within random phase approximation, we show that the Coulomb repulsion is strongly screened around the mori\'e length scale, resulting in attractive regimes that facilitate electron pairing in unconventional channels. By solving the linearized gap equation, we find that the maxima of the superconducting critical temperature occur at the van Hove singularities in the density of states, with magnitude on the order of $\sim$0.2 K, comparable with experimental observations. Moreover, we identify a phase transition from an $f$-wave-like pairing state to a doubly degenerate $d$-wave-like pairing state upon increasing the electric displacement field. These findings provide a purely electronic explanation of the superconducting state observed in twisted bilayer WSe$_2$, offering insights into the interplay between superconductivity and other correlated states in twisted transition metal dichalcogenides.