Evolution of the local superconducting density of states in ErRh$_4$B$_{4}$ close to the ferromagnetic transition

TL;DR

This study investigates how the local superconducting density of states in ErRh$_4$B$_{4}$ evolves near the ferromagnetic transition, revealing abrupt changes and coexistence phenomena through tunneling spectroscopy.

Contribution

It provides new insights into the local electronic states and phase coexistence in a reentrant superconductor near its magnetic transition.

Findings

Tunneling conductance jumps from normal to superconducting near the transition.

No superconducting correlations detected within the ferromagnetic phase.

V-shaped density of states observed in the superconducting phase due to magnetic modulation.

Abstract

We present local tunneling spectroscopy experiments in the superconducting and ferromagnetic phases of the reentrant superconductor ErRh$_4$B$_{4}$. The tunneling conductance curves jump from showing normal to superconducting features within a few mK close to the ferromagnetic transition temperature, with a clear hysteretic behavior. Within the ferromagnetic phase, we do not detect any superconducting correlations. Within the superconducting phase we find a peculiar V-shaped density of states at low energies, which is produced by the magnetically modulated phase that coexists with superconductivity just before ferromagnetism sets in.