Nonreciprocal Josephson linear response

TL;DR

This paper explores how multiterminal Josephson junctions exhibit non-reciprocal linear responses at finite frequencies, revealing potential for non-dissipative, on-chip microwave circulators driven by symmetry-breaking effects.

Contribution

It demonstrates non-reciprocal linear response in multiterminal Josephson junctions at finite frequencies, highlighting dynamic effects and potential applications in non-dissipative microwave devices.

Findings

Non-reciprocal reactive response outside Andreev resonances

Microwave transmission can be nearly fully non-reciprocal

Potential for small-scale, low-field on-chip circulators

Abstract

We consider the finite-frequency response of multiterminal Josephson junctions and show how non-reciprocity in them can show up at linear response, in contrast to the static Josephson diodes featuring non-linear non-reciprocity. At finite frequencies, the response contains dynamic contributions to the Josephson admittance, featuring the effects of Andreev bound state transitions along with Berry phase effects, and reflecting the breaking of the same symmetries as in Josephson diodes. We show that outside exact Andreev resonances, the junctions feature non-reciprocal reactive response. As a result, the microwave transmission through those systems is non-dissipative, and the electromagnetic scattering can approach complete non-reciprocity. Besides providing information about the nature of the weak link energy levels, the non-reciprocity can be utilized to create non-dissipative and small-scale on-chip circulators whose operation requires only rather small magnetic fields.