Effect of Cu doping on superconductivity in TaSe₃: Relationship between superconductivity and induced charge density wave

¹ Department of Applied Physics, Hokkaido University - Sapporo 060-8628, Japan
² Center of Education and Research for Topological Science and Technology, Hokkaido University Sapporo 060-8628, Japan

Received: 23 August 2018
Accepted: 5 December 2018

Abstract

By measuring the temperature dependence of the resistance, we investigated the effect of Cu doping on superconductivity (SC) in Cu-doped TaSe₃ in which the charge density wave (CDW) transition is induced by Cu doping. We observed an emergence of a region where the SC transition temperature (T_C) decreased in samples with higher Cu concentrations and found that the region tended to expand with increasing Cu concentration. In addition, the temperature dependence of the upper critical field (H_C2) of Cu-doped TaSe₃ was found to differ from that of pure TaSe₃. Based on these experimental results and the fact that the SC of TaSe₃ is filamentary, we conclude that SC is suppressed locally by Cu doping and competes with the CDW in Cu-doped TaSe₃. The resistance anomaly due to the CDW transition was extremely small and the size of the anomaly was enhanced with increasing Cu concentration but the temperature at which the anomaly appeared hardly changed. These results of the anomaly and the local suppression of SC suggest that the induced CDWs have short-range order in the vicinity of Cu atoms. We also discuss the effect of the pinning of CDWs on the relationship between SC and short-range order CDWs.