Observation of anisotropic effect of antiferromagnetic ordering on the superconducting gap in ErNi2B2C

TL;DR

This study investigates how antiferromagnetic ordering in ErNi2B2C affects its superconducting gap, revealing anisotropic suppression of the gap below the magnetic transition temperature using point-contact spectroscopy and theoretical models.

Contribution

It provides the first detailed analysis of the anisotropic impact of magnetic ordering on the superconducting gap in ErNi2B2C using advanced modeling and spectroscopy.

Findings

Superconducting gap decreases by 25% in the c-direction below T_N.

Gap decreases by only 4% in the ab-plane below T_N.

Pair-breaking effects are more pronounced in the c-direction near magnetic transitions.

Abstract

The point-contact (PC) spectra of the Andreev reflection dV/dI curves of the superconducting rare-earth nickel borocarbide ErNi2B2C (Tc=11 K) have been analyzed in the "one-gap" and "two-gap" approximations using the generalized Blonder-Tinkham-Klapwijk (GBTK) model and the Beloborod'ko (BB) model allowing for the pair-breaking effect of magnetic impurities. Experimental and calculated curves have been compared not only in shape, but in magnitude as well, which provide more reliable data for determining the temperature dependence of the energy gap (or superconducting order parameter) \Delta(T). The anisotropic effect of antiferromagnetic ordering at T_N =6 K on the superconducting gap/order parameter has been determined: as the temperature is lowered, \Delta(T) decreases by 25% in the c-direction and only by 4% in the ab-plane. It is found that the pair-breaking parameter increases in the vicinity of the magnetic transitions, the increase being more pronounced in the c-direction. The efficiency of the models was tested for providing \Delta(T) data for ErNi2B2C from Andreev reflection spectra.