Identifying the odd-frequency superconducting state by a field-induced Josephson effect

TL;DR

This paper proposes a method to identify bulk odd-frequency superconductors by observing a field-induced Josephson current between even- and odd-frequency superconductors, which normally do not exhibit such a current.

Contribution

It demonstrates that an exchange field can induce a Josephson current between diffusive even- and odd-frequency superconductors, providing a new experimental signature for odd-frequency pairing.

Findings

Exchange field induces Josephson current between even- and odd-frequency superconductors.

The method offers a way to experimentally detect bulk odd-frequency superconductivity.

Potential implications for understanding and utilizing unconventional superconducting states.

Abstract

Superconducting order parameters that are odd under exchange of time-coordinates of the electrons constituting a Cooper-pair, are potentially of great importance both conceptually and technologically. Recent experiments report that such an odd-frequency superconducting {\it bulk} state may be realized in certain heavy-fermion compounds. While the Josephson current normally only flows between superconductors with the same symmetries with respect to frequency, we demonstrate that an exchange field may induce a current between diffusive even- and odd-frequency superconductors. This suggests a way to identify the possible existence of bulk odd-frequency superconductors.