Conductance signatures of odd-frequency superconductivity in quantum spin Hall systems using a quantum point contact

TL;DR

This paper proposes a system combining a quantum point contact and proximity-induced s-wave superconductivity at a 2D topological insulator edge to detect odd-frequency pairing through transport signatures, without breaking time-reversal symmetry.

Contribution

It introduces a novel setup for identifying odd-frequency superconductivity via transport signatures in topological insulators, avoiding the need for time-reversal symmetry breaking.

Findings

Crossed Andreev reflection dominates over electron cotunneling.

Transport signatures directly indicate odd-frequency pairing.

No time-reversal symmetry breaking required.

Abstract

Topological superconductors give rise to unconventional superconductivity, which is mainly characterized by the symmetry of the superconducting pairing amplitude. However, since the symmetry of the superconducting pairing amplitude is not directly observable, its experimental identification is rather difficult. In our work, we propose a system, composed of a quantum point contact and proximity induced s-wave superconductivity at the helical edge of a two dimensional topological insulator, for which we demonstrate the presence of odd-frequency pairing and its intimate connection to unambiguous transport signatures. Notably, our proposal requires no time-reversal symmetry breaking terms. We discover the domination of crossed Andreev reflection over electron cotunneling in a wide range of parameter space, which is a quite unusual transport regime.