Robust superconductivity and the suppression of charge-density wave in $\text{Ca}_{3}(\text{Ir}_{1-x}\text{Rh}_{x})_{4}\text{Sn}_{13}$ single crystals at ambient pressure

TL;DR

This study investigates how substituting Rh for Ir in Ca3Ir4Sn13 affects superconductivity and charge-density wave (CDW), revealing their competition and potential quantum critical point at ambient pressure.

Contribution

It provides the first detailed phase diagram showing the suppression of CDW and enhancement of superconductivity with Rh substitution in Ca3Ir4Sn13.

Findings

CDW transition temperature decreases with Rh doping and vanishes near x=0.58.

Superconducting transition temperature slightly increases with Rh doping.

Evidence of a fully-gapped Fermi surface from penetration depth measurements.

Abstract

Single crystals of Ca$_3$(Ir$_{1-x}$Rh$_x$)$_4$Sn$_{13}$ (3-4-13) were synthesized by flux growth and characterized by X-ray diffraction, EDX, magnetization, resistivity and radio frequency magnetic susceptibility tunnel diode resonator (TDR) techniques. Compositional variation of the Rh/Ir ratio was used to study the coexistence and competition between the charge density wave (CDW) and superconductivity. The superconducting transition temperature varies from approximately 7 K in pure Ir ($x=0$) to approximately 8.3 K in pure Rh ($x=1$). Temperature-dependent electrical resistivity reveals monotonic suppression of the CDW transition temperature, $T_{\text{CDW}}(x)$. The CDW starts in pure Ir, $x=0$, with $T_{\text{CDW}}\approx40$~K and extrapolates roughly linearly to zero at $x_c=0.58$ under the dome of superconductivity. Magnetization and transport measurements show a significant influence of CDW on the superconducting and normal state. Vortex pinning is substantially enhanced in the CDW region, and the resistivity is larger in this part of the phase diagram. The London penetration depth is attenuated exponentially upon cooling at low temperatures for all compositions, indicating a fully-gapped Fermi surface. We conclude that a novel $\text{Ca}_3(\text{Ir}_{1-x}\text{Rh}_x)_4\text{Sn}_{13}$ alloy with coexisting/competing CDW and superconductivity, is a good candidate to look for a composition-driven quantum critical point at ambient pressure.