Phase-tunable electron transport assisted by odd-frequency Cooper pairs in topological Josephson junctions

TL;DR

This paper investigates how phase-tunable electron transport in topological Josephson junctions reveals the exclusive role of odd-frequency Cooper pairs, offering a new detection method for these elusive pairs.

Contribution

It demonstrates that finite-size topological Josephson junctions can be used to detect odd-frequency Cooper pairs through phase-controlled electron transport.

Findings

Transport is highly tunable by phase difference .

At  and zero frequency, local Andreev reflection vanishes.

Odd-frequency Cooper pairs dominate transport inside the junction.

Abstract

We consider a finite-size topological Josephson junction formed at the edge of a two-dimensional topological insulator in proximity to conventional superconductors and study the impact of Cooper pair symmetries on the electron transport. We find that, due to the finite junction size, electron transport is highly tunable by the superconducting phase difference $\phi$ across the junction. At zero frequency and $\phi=\pi$, the setup exhibits vanishing local Andreev reflection and perfect normal transmission due to the interplay of finite junction size and formation of topological Andreev bound states in the middle of the junction. We reveal that this striking behavior enables odd-frequency Cooper pairs to become the only type of pairing inside the topological junction that contribute to transport. Our paper thus offers a highly tunable detection scheme for odd-frequency Cooper pairs.