Evidence for the Coexistence of Anisotropic Superconducting Gap and Nonlocal Effects in the Non-magnetic Superconductor LuNi2B2C

TL;DR

This paper investigates how anisotropic superconducting gaps and nonlocal effects coexist in LuNi2B2C, revealing complex heat capacity behaviors influenced by disorder and magnetic field orientation.

Contribution

It provides experimental evidence of the coexistence of anisotropic gaps and nonlocal effects in a non-magnetic superconductor, highlighting disorder's impact on heat capacity patterns.

Findings

Pure samples show fourfold heat capacity variation with field rotation.

Disordered samples develop secondary minima, leading to an 8-fold pattern.

Results suggest interplay between gap anisotropy and nonlocal effects.

Abstract

A study of the dependence of the heat capacity Cp(alpha) on field angle in LuNi2B2C reveals an anomalous disorder effect. For pure samples, Cp(alpha) exhibits a fourfold variation as the field H < Hc2 is rotated in the [001] plane, with minima along <100> (alpha = 0). A slightly disordered sample, however, develops anomalous secondary minima along <110> for H > 1 T, leading to an 8-fold pattern. The anomalous pattern is discussed in terms of coexisting superconducting gap anisotropy and non-local effects.