A New Superconducting 3R-WS2 Phase at High Pressure.

ABSTRACT

High-pressure investigation has been shown to be of paramount significance for changing the conventional lattice or bringing fascinating properties, especially inducing superconducting phases. Here we studied the application of pressure to the recently synthesized 2M-WS2 with the record Tc (8.8 K) among transition metal dichalcogenides (TMDs) at ambient pressure by electrical resistance investigations, synchrotron X-ray studies, and theoretical calculations. Tc in the initial 2M-WS2 dropped from the maximum to become undetected, accompanied by a phase transition into a semiconductor, 3R-WS2, at 15 GPa. The successive metallization and superconducting transitions in 3R-WS2 were observed at 48.8 GPa with Tc ≈ 2.5 K. This is the first experimental case in which superconductivity has been realized in the 3R phase among TMDs. We propose that the degradation of superconductivity in 2M-WS2 and the reemergence of superconductivity in 3R-WS2 are mainly attributable to changes in the density of states near the Fermi surface driven by the interlayer coupling.