Tuning the Charge Density Wave and Superconductivity in CuxTaS2

TL;DR

This study explores how copper doping affects charge density wave and superconductivity in CuxTaS2, revealing an optimal doping level that enhances superconducting transition temperature while modifying the CDW properties.

Contribution

It provides the first detailed phase diagram of CuxTaS2 showing the interplay between CDW suppression and superconductivity enhancement with Cu doping.

Findings

Superconducting transition temperature peaks at 4.5 K at x=0.04

Charge density wave persists at optimal doping with altered q vector

Electronic specific heat shows non-monotonic behavior with doping

Abstract

We report the characterization of layered, 2H-type CuxTaS2, for x between 0 and 0.12. The charge density wave (CDW), at 70 K for TaS2, is destabilized with Cu doping. The sub-1K superconducting transition in undoped 2H-TaS2 jumps quickly to 2.5 K at low x, increases to 4.5 K at the optimal composition Cu0.04TaS2, and then decreases at higher x. The electronic contribution to the specific heat, first increasing and then decreasing as a function of Cu content, is 12 mJ mol-1 K-2 at Cu0.04TaS2. Electron diffraction studies show that the CDW remains present at the optimal superconducting composition, but with both a changed q vector and decreased coherence length. We present an electronic phase diagram for the system.