New Superconductivity in Layered 1T-TaS2-xSex Single Crystals Fabricated by Chemical Vapor Transport

TL;DR

This study reports the discovery of superconductivity in layered 1T-TaS2-xSex single crystals fabricated via chemical vapor transport, revealing a new way to induce superconductivity through chalcogen substitution.

Contribution

It is the first demonstration of superconductivity induced by substituting S with Se in 1T-TaS2, challenging previous notions that high pressure or Ta-site substitution were necessary.

Findings

Superconductivity appears across a wide Se content range within the NCCDW phase.

The Mott phase transitions to NCCDW and then to CCDW with increasing Se content.

Superconductivity is linked to the robust Ta 5d band, indicating a universal behavior in 1T-TaS2 systems.

Abstract

Layered transition-metal dichalcogenides 1T-TaS2-xSex (0<=x<=2) single crystals have been successfully fabricated by using a chemical vapor transport technique in which Ta locates in octahedral coordination with S and Se atoms. This is the first superconducting example by the substitution of S site, which violates an initial rule based on the fact that superconductivity merely emerges in 1T-TaS2 by applying the high pressure or substitution of Ta site. We demonstrate the appearance of a series of electronic states in 1T-TaS2-xSex with Se content. Namely, the Mott phase melts into a nearly commensurate charge-density-wave (NCCDW) phase, superconductivity in a wide x range develops within the NCCDW state, and finally commensurate charge-density-wave (CCDW) phase reproduces for heavy Se content. The present results reveal that superconductivity is only characterized by robust Ta 5d band, demonstrating the universal nature in 1T-TaS2 systems that superconductivity and NCCDW phase coexist in the real space.