Transport signatures of superconducting hybrids with mixed singlet and chiral triplet states

TL;DR

This paper models a superconductor with coexisting singlet and chiral triplet pairings, revealing topological phase transitions and unique conductance signatures, including zero-bias peaks and zero-energy Andreev bound states.

Contribution

It introduces a comprehensive model for mixed singlet and triplet superconductivity and explores its experimental signatures and topological properties.

Findings

Identification of two effective gaps due to mixed pairing

Topological phase transition with zero-bias conductance peak

Presence of zero-energy Andreev bound states in non-trivial phase

Abstract

We propose a model for a superconductor where both spin-singlet and chiral triplet pairing amplitudes can coexist. By solving the Bogoliubov-de Gennes equations with a general pair potential that accounts for both spin states we study experimental signatures of normal metal and superconductor hybrids. The interplay between the spin-singlet and triplet correlations manifests in the appearance of two effective gaps. When the amplitude of the spin-triplet component is stronger than that of the spin-singlet, a topological phase transition into a non-trivial regime occurs. As a result, the normal metal-superconductor conductance evolves from a conventional gap profile onto an unconventional zero-bias peak. Additionally, in the topologically non-trivial phase, Andreev bound states formed at Josephson junctions present zero-energy modes; the number of those modes depends on the relative chirality of the junction. Finally, we present results for the current-phase relation and the temperature dependence of the Josephson critical current within both topological phases for several system parameters.