Particle-hole spectral asymmetry at the edge of multiorbital noncentrosymmetric superconductors

TL;DR

This paper reveals that in certain two-dimensional noncentrosymmetric superconductors with multiorbital spin-triplet pairing, the edge spectral function can exhibit particle-hole asymmetry due to orbital splitting and reduced symmetry, offering new ways to detect complex pairing states.

Contribution

It demonstrates that edge spectral asymmetry arises from orbital splitting and mixed parity pairing in noncentrosymmetric superconductors, a novel insight into their edge states.

Findings

Edge spectral functions can be particle-hole asymmetric.

Orbital splitting influences pairing states at the edge.

Asymmetry can be used to detect spin-triplet pairing with internal degrees of freedom.

Abstract

Bogoliubov quasiparticles are a coherent electron-hole quantum superposition which typically, for time-reversal symmetric superconductors, exhibit a spectral distribution with particle-hole symmetry. Here, we demonstrate that in two-dimensional noncentrosymmetric superconductors with multiorbital spin-triplet pairing the energy profile of the density of states at the edge can violate this paradigm. We show that the structure of Andreev reflections generally leads to pairing states made of configurations that are orbitally split due to the low degree of crystalline symmetry at the edge. The resulting pairing state has a mixed parity character in the orbital sector that, in the presence of reduced crystal symmetry at the edge, sets out a particle-hole asymmetric profile for the spectral function. These findings indicate a path to design asymmetric spectral functions at the edge of superconductors with orbital degrees of freedom and time-reversal symmetry. The emerging signatures can be exploited for the detection of spin-triplet pairing equipped with internal degrees of freedom.