Anomalous Andreev interferometer: Study of an anomalous Josephson junction coupled to a normal wire

TL;DR

This paper explores how phase shifts in anomalous Josephson junctions influence the resistance and quasiparticle currents in Andreev interferometers, providing a new method to probe the $\,\phi_0$ effect.

Contribution

It demonstrates that the phase shift in $\,\phi_0$-junctions causes measurable effects in Andreev interferometers, introducing a novel way to detect the $\,\phi_0$ effect.

Findings

Resistance oscillates with phase in the interferometer.

Anomalous quasiparticle current exists at finite $\,\phi_0$.

Proposed two realizations: spin-orbit coupled and spin-split superconductors.

Abstract

Josephson junctions (JJs), where both time-reversal and inversion symmetry are broken, exhibit a phase shift $\phi_0$ in their current-phase relation. This allows for an anomalous supercurrent to flow in the junction even in the absence of a phase bias between the superconductors. We show that a finite phase shift also manifests in the so-called Andreev interferometers - a device that consists of a mesoscopic conductor coupled to the $\phi_0$-junction. Due to the proximity effect, the resistance of this conductor is phase-sensitive - it oscillates by varying the phase of the JJ. As a result, the quasiparticle current $I_{\mathrm{qp}}$ flowing through the conductor has an anomalous component, which exists only at finite $\phi_0$. Thus, the Andreev interferometry could be used to probe the $\phi_0$ effect. We consider two realizations of the $\phi_0$-junction and calculate $I_{\mathrm{qp}}$ in the interferometer: a superconducting structure with spin-orbit coupling and a system of spin-split superconductors with spin-polarized tunneling barriers.