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

摘要

We theoretically investigate the possibility of achieving a superconductingstate in transition-metal dichalcogenide bilayers through intercalation, aprocess previously and widely used to achieve metallization and superconductingstates in novel superconductors. For the Ca-intercalated bilayers MoS$_2$ andWS$_2$, we find that the superconducting state is characterized by anelectron-phonon coupling constant larger than $1.0$ and a superconductingcritical temperature of $13.3$ and $9.3$ K, respectively. These results aresuperior to other predicted or experimentally observed two-dimensionalconventional superconductors and suggest that the investigated materials may begood candidates for nanoscale superconductors. More interestingly, we provedthat the obtained thermodynamic properties go beyond the predictions of themean-field Bardeen--Cooper--Schrieffer approximation and that the calculationsconducted within the framework of the strong-coupling Eliashberg theory shouldbe treated as those that yield quantitative results.