Revealing inter-band electron pairing in a superconductor with spin-orbit coupling

TL;DR

This study uncovers inter-band electron pairing in a superconductor with strong spin-orbit coupling, using scanning tunneling spectroscopy to analyze Yu-Shiba-Rusinov states and quasiparticle interference patterns, revealing unconventional pairing mechanisms.

Contribution

It demonstrates the existence of inter-band pairing in ipd\, highlighting the role of spin-orbit coupling and band hybridization in unconventional superconductivity.

Findings

Inter-band pairing observed via BQPI analysis.

Selective inter-band scattering processes contribute to superconductivity.

Band hybridization influences pairing mechanisms.

Abstract

Most superconducting mechanisms pair electrons within the same band, forming spin singlets. However, the discovery of multi-band superconductivity has opened new scenarios for pairing, particularly in systems with strong spin-orbit coupling. Here, we reveal inter-band pairing in the superconductor \bipd\ by mapping the amplitude of sub-gap Yu-Shiba-Rusinov (YSR) states around Vanadium adatoms deposited on its surface. The surface of \bipd\ is characterized by spin-helical-like bands near the Fermi level. Scanning tunneling spectroscopy reveals anisotropic YSR amplitude oscillations around the impurity, driven by spin-conserving Bogoliubov quasiparticle interference (BQPI). Analysis of the BQPI patterns at the YSR energy exposes inter-band pairing in this material. Interestingly, only a small subset of all possible inter-band scattering processes observed in the normal state contribute to the BQPI patterns. Combining experimental data and theory, we demonstrate that the observed band selectivity results from the hybridization of the band coupled with the impurity with other bands. Our findings reveal unconventional pairing mechanisms in \bipd\ and highlight the crucial role of spin-orbit interactions in their formation.