Strong-coupling superconductivity induced by calcium intercalation in bilayer transition-metal dichalcogenides

TL;DR

This paper predicts strong-coupling superconductivity in calcium-intercalated bilayer transition-metal dichalcogenides, with high critical temperatures and properties beyond BCS theory, suggesting their potential as nanoscale superconductors.

Contribution

It demonstrates that calcium intercalation induces strong-coupling superconductivity in bilayer MoS₂ and WS₂, with detailed Eliashberg theory analysis providing accurate thermodynamic predictions.

Findings

Superconducting T_c of 13.3 K in Ca-intercalated MoS₂

Superconducting T_c of 9.3 K in Ca-intercalated WS₂

Strong electron-phonon coupling constant > 1.0

Abstract

We theoretically investigate the possibility of achieving a superconducting state in transition-metal dichalcogenide bilayers through intercalation, a process previously and widely used to achieve metallization and superconducting states in novel superconductors. For the Ca-intercalated bilayers MoS$_2$ and WS$_2$, we find that the superconducting state is characterized by an electron-phonon coupling constant larger than $1.0$ and a superconducting critical temperature of $13.3$ and $9.3$ K, respectively. These results are superior to other predicted or experimentally observed two-dimensional conventional superconductors and suggest that the investigated materials may be good candidates for nanoscale superconductors. More interestingly, we proved that the obtained thermodynamic properties go beyond the predictions of the mean-field Bardeen--Cooper--Schrieffer approximation and that the calculations conducted within the framework of the strong-coupling Eliashberg theory should be treated as those that yield quantitative results.