Superconductivity in potassium-doped metallic polymorphs of MoS2

TL;DR

This study demonstrates that potassium intercalation induces superconductivity in metallic polymorphs of MoS2, expanding the family of superconducting transition metal dichalcogenides and revealing phase transitions linked to doping levels.

Contribution

It is the first to show superconductivity in 1T and 1T' MoS2 polymorphs via potassium doping, with associated structural and electronic phase transitions.

Findings

Superconductivity observed at 2.8K in 1T-MoS2

Superconductivity observed at 4.6K in 1T'-MoS2

Potassium intercalation causes structural and superconducting phase transitions

Abstract

Superconducting layered transition metal dichalcogenides (TMDs) stand out among other superconductors due to the tunable nature of the superconducting transition, coexistence with other collective electronic excitations (charge density waves) and strong intrinsic spin-orbit coupling. Molybdenum disulphide (MoS2) is the most studied representative of this family of materials, especially since the recent demonstration of the possibility to tune its critical temperature, Tc, by electric-field doping. However, just one of its polymorphs, band-insulator 2H-MoS2, has so far been explored for its potential to host superconductivity. We have investigated the possibility to induce superconductivity in metallic polytypes, 1T- and 1T'-MoS2, by potassium (K) intercalation. We demonstrate that at doping levels significantly higher than that required to induce superconductivity in 2H-MoS2, both 1T and 1T' phases become superconducting, with Tc = 2.8 and 4.6K, respectively. Unusually, K intercalation in this case is responsible both for the structural and superconducting phase transitions. By adding new members to the family of superconducting TMDs our findings open the way to further manipulate and enhance the electronic properties of these technologically important materials.