Singlet superconductivity in single-crystal NiBi3 superconductor

TL;DR

This study uses Andreev reflection spectroscopy to investigate the superconducting properties of NiBi3, revealing it as a singlet s-wave superconductor with specific gap characteristics and spin state.

Contribution

It provides the first detailed analysis of the superconducting gap symmetry and spin state in NiBi3 using advanced spectroscopy techniques.

Findings

NiBi3 is a singlet s-wave superconductor.

The superconducting gap value and temperature dependence were determined.

The spin state in NiBi3 is antiparallel, indicating singlet pairing.

Abstract

Andreev reflection spectroscopy with unpolarized and highly spin-polarized currents has been utilized to study an intermetallic single-crystal superconductor NiBi3. Magnetoresistance at zero bias voltage of point contacts shows the occurrence and suppression of Andreev reflection by unpolarized and polarized current, respectively. The gap value, its symmetry and temperature dependence have been determined using an unpolarized current. The spin state in the NiBi3 sample is determined to be antiparallel using a highly spin-polarized current. The gap value 2Delta/kBT, gap symmetry and its temperature dependence, combined with the antiparallel spin state show that the bulk NiBi3 is a singlet s-wave superconductor.