Anomalous thermopower and Nernst effect in $\rm CeCoIn_5$: entropy-current loss in precursor state

TL;DR

This study investigates the anomalous thermoelectric properties of CeCoIn$_5$ in its precursor state, revealing a significant entropy-current loss and enhanced Nernst signal that suggest phase coherence and unconventional electronic behavior above superconductivity.

Contribution

It uncovers the entropy-current loss and thermoelectric anomalies in CeCoIn$_5$'s precursor state, providing new insights into its electronic entropy and phase coherence mechanisms.

Findings

Entropy current decreases steeply below 15 K, reaching near zero at T_c.

Enhanced off-diagonal thermoelectric current $eta_{xy}$ in the precursor state.

Anomalous thermopower and Nernst signals contrast with weak resistivity and magnetization effects.

Abstract

The heavy-electron superconductor CeCoIn$_5$ exhibits a puzzling precursor state above its superconducting critical temperature at $T_c$ = 2.3 K. The thermopower and Nernst signal are anomalous. Below 15 K, the entropy current of the electrons undergoes a steep decrease reaching $\sim$0 at $T_c$. Concurrently, the off-diagonal thermoelectric current $\alpha_{xy}$ is enhanced. The delicate sensitivity of the zero-entropy state to field implies phase coherence over large distances. The prominent anomalies in the thermoelectric current contrast with the relatively weak effects in the resistivity and magnetization.