Ca$_3$Ir$_4$Sn$_{13}$: A weakly correlated nodeless superconductor

TL;DR

This study characterizes Ca$_3$Ir$_4$Sn$_{13}$ as a weakly correlated superconductor with a nodeless gap, revealing Fermi surface reconstruction and charge density wave transition through thermoelectric and specific heat measurements.

Contribution

It provides detailed experimental evidence of Fermi surface changes and superconducting gap structure in Ca$_3$Ir$_4$Sn$_{13}$, highlighting its weak correlation and nodeless superconductivity.

Findings

Fermi surface reconstruction at $T^*$

Charge density wave gap opening

Nodeless superconducting gap

Abstract

We report detailed Seebeck coefficient, Hall resistivity as well as specific heat measurement on Ca$_3$Ir$_4$Sn$_{13}$ single crystals. The Seebeck coefficient exhibits a peak corresponding to the anomaly in resistivity at $T^*$, and the carrier density is suppressed significantly below $T^*$. This indicates a significant Fermi surface reconstruction and the opening of the charge density wave gap at the supperlattice transition. The magnetic field induced enhancement of the residual specific heat coefficient $\gamma(H)$ exhibits a nearly linear dependence on magnetic field, indicating a nodeless gap. In the temperature range close to $T_c$ the Seebeck coefficient can be described well by the diffusion model. The zero-temperature extrapolated thermoelectric power is very small, implying large normalized Fermi temperature. Consequently the ratio $\frac{T_c}{T_F}$ is very small. Our results indicate that Ca$_3$Ir$_4$Sn$_{13}$ is a weakly correlated nodeless superconductor.