Thermoelectric signature of quantum criticality in the heavy-fermion superconductor CeRhIn$_5$

TL;DR

This study uses thermopower measurements to explore Fermi surface changes across quantum critical points in CeRhIn$_5$, revealing different behaviors in pure and doped samples that help distinguish types of quantum criticality.

Contribution

It demonstrates the effectiveness of thermopower measurements in identifying the nature of quantum criticality in heavy-fermion superconductors.

Findings

Pure CeRhIn$_5$ shows a Fermi surface reconstruction at the QCP.

Doped CeRhIn$_5$ exhibits symmetric thermopower behavior around the QCP.

Thermopower behavior aligns with theoretical models of quantum criticality.

Abstract

The evolution of the Fermi surface across the quantum critical point (QCP), which is relevant for characterizing the quantum criticality and understanding its relation with unconventional superconductivity, is an intriguing subject in the study of strongly correlated electron systems. In this study, we report the thermopower measurements to investigate a change in Fermi surface across the QCP in pure and 4.4% Sn-doped CeRhIn$_5$. Results show that their thermopower behavior differs significantly in the vicinity of their respective pressure-induced QCP. In pure CeRhIn$_5$, a drastic collapse of the thermopower takes place at the Kondo breakdown QCP, where the Fermi surface reconstructs concurrently with the development of the magnetic order. By contrast, the thermopower exhibits a broadly symmetric behavior around the QCP in 4.4% Sn-doped CeRhIn$_5$, which is a characteristic of the spin-density-wave QCP. These observations are consistent with the theoretical expectations and suggest the effectiveness of thermopower measurement in discriminating the nature of quantum criticality in heavy-fermion systems.