Competition of multiband superconducting and magnetic order in ErNi2B2C observed by Andreev reflection

TL;DR

This study uses point contact Andreev reflection spectroscopy to investigate the coexistence and competition of superconducting and magnetic orders in ErNi2B2C, revealing two superconducting order parameters and their suppression below the Neel temperature.

Contribution

It demonstrates for the first time the existence of two superconducting order parameters in ErNi2B2C and analyzes their temperature dependence in the presence of magnetic order.

Findings

Retention of Andreev reflection minima up to Tc

Existence of two superconducting order parameters

Suppression of order parameters below T_N

Abstract

Point contacts (PC) Andreev reflection dV/dI spectra for the antiferromagnetic (T_N =6K) superconductor (Tc=11K) ErNi2B2C have been measured for the two main crystallographic directions. Observed retention of the Andreev reflection minima in dV/dI up to Tc directly points to unusual superconducting order parameter (OP) vanishing at Tc. Temperature dependence of OP was obtained from dV/dI using recent theory of Andreev reflection including pair-breaking effect. For the first time existence of a two superconducting OPs in ErNi2B2C is shown. A distinct decrease of both OPs as temperature is lowered below T_N is observed.