Strong-Coupling Superconductivity of CeIrSi$_3$ with the Non-centrosymmetric Crystal Structure

TL;DR

This study investigates the pressure-induced superconductivity in CeIrSi3, revealing strong-coupling behavior with a notably large heat capacity jump, and maps the phase diagram showing the coexistence of antiferromagnetism and superconductivity.

Contribution

It provides the first detailed high-pressure measurements of resistivity and heat capacity in CeIrSi3, demonstrating strong-coupling superconductivity in a non-centrosymmetric crystal structure.

Findings

Maximum T_sc of 1.6 K near 2.5-2.7 GPa

Largest heat capacity jump among known superconductors

Superconducting state persists up to 3.5 GPa

Abstract

We studied the pressure-induced superconductor CeIrSi$_3$ with the non-centrosymmetric tetragonal structure under high pressure. The electrical resistivity and ac heat capacity were measured in the same run for the same sample. The critical pressure was determined to be $P_{\rm c}$ = 2.25 GPa, where the antiferromagnetic state disappears. The heat capacity $C_{\rm ac}$ shows both antiferromagnetic and superconducting transitions at pressures close to $P_{\rm c}$. On the other hand, the superconducting region is extended to high pressures of up to about 3.5 GPa, with the maximum transition temperature $T_{\rm sc}$ = 1.6 K around $2.5-2.7$ GPa. At 2.58 GPa, a large heat capacity anomaly was observed at $T_{\rm sc}$ = 1.59 K. The jump of the heat capacity in the form of ${\Delta}{C_{\rm ac}}/C_{\rm ac}(T_{\rm sc})$ is 5.7 $\pm$ 0.1. This is the largest observed value among previously reported superconductors, indicating the strong-coupling superconductivity. The electronic specific heat coefficient at $T_{\rm sc}$ is, however, approximately unchanged as a function of pressure, even at $P_{\rm c}$.