Enhanced superconductivity with possible re-appearance of charge density wave states in polycrystalline Cu$_{1-x}$Ag$_x$Ir$_2$Te$_4$ alloys

TL;DR

This study investigates how doping CuIr2Te4 with Ag affects its superconductivity and charge density wave states, revealing a phase diagram with re-entrant charge density waves and a maximum Tc of 2.93 K.

Contribution

It provides the first detailed phase diagram showing the interplay of superconductivity and charge density waves in Cu$_{1-x}$Ag$_x$Ir$_2$Te$_4$ alloys, including re-entrant CDW states.

Findings

Superconducting Tc reaches 2.93 K at 12% Ag doping.

Re-entrant charge density wave states appear at high doping levels.

Critical magnetic fields vary with doping, indicating changes in superconducting properties.

Abstract

In this study, we determined the effect of doping with the noble metal Ag on Ir$_2$Te$_4$ superconductors. Based on the resistivity, magnetization, and heat capacity, we explored the changes in the superconductivity and charge density wave for Cu$_{1-x}$Ag$_x$Ir$_2$Te$_4$ as a function of isoelectric substitution. We assessed a complete set of competing states from suppressed charge density wave in the low doping region to superconductor in the middle doping region and re-entrant charge density wave in the high doping region, thereby obtaining an electronic phase diagram, where the superconducting dome was near bipartite charge density wave regions with a maximum superconducting temperature Tc of about 2.93 K at an Ag doping level of 12%. The lower H$_{c1}$ and upper H$_{c2}$ critical magnetic fields were determined for some representative samples in the Cu$_{1-x}$Ag$_x$Ir$_2$Te$_4$ series based on magnetization and resistivity measurements, respectively. We showed that H$_{c1}$ decreased whereas H$_{c2}$ increased as the doping content increased. The specific heat anomalies at the superconducting transitions $\Delta C_{el}/\gamma T_c$ for representative samples comprising Cu$_{0.92}$Ag$_{0.08}$Ir$_2$Te$_4$, Cu$_{0.88}$Ag$_{0.12}$Ir$_2$Te$_4$, and Cu$_{0.85}$Ag$_{0.15}$Ir$_2$Te$_4$ were approximately 1.40, 1.44, and 1.42, respectively, which are all near the Bardeen-Cooper-Schrieffer value of 1.43 and they indicate bulk superconductivity in these compounds.