Controllable odd-frequency Cooper pairs in multi-superconductor Josephson junctions

TL;DR

This paper investigates how multi-superconductor Josephson junctions can host controllable nonlocal odd-frequency Cooper pairs, revealing their dominance in nonlocal conductance and phase-dependent properties.

Contribution

It introduces the concept of phase-controlled nonlocal odd-frequency pairing in multi-superconductor junctions, expanding the classification of pair symmetries and providing evidence through conductance measurements.

Findings

Nonlocal odd-frequency pairs are dominant at phase difference π.

Superconducting phases enable control over pair symmetries.

Nonlocal conductance is significantly influenced by odd-frequency pairs.

Abstract

We consider Josephson junctions formed by multiple superconductors with distinct phases and explore the formation of nonlocal or inter-superconductor pair correlations. We find that the multiple superconductor nature offers an additional degree of freedom that broadens the classification of pair symmetries, enabling nonlocal even- and odd-frequency pairings that can be highly controlled by the superconducting phases and the energy of the superconductors. Specially, when the phase difference between two superconductors is $\pi$, their associated nonlocal odd-frequency pairing is the only type of inter-superconductor pair correlations. Finally, we show that these nonlocal odd-frequency Cooper pairs dominate the nonlocal conductance via crossed Andreev reflections, which constitutes a direct evidence of odd-frequency pairing.