Flux-tunable Josephson Effect in a Four-Terminal Junction

TL;DR

This study demonstrates a phase-tunable four-terminal Josephson junction in an InSbAs 2DEG, revealing nonlocal effects and phase offsets that mimic multiterminal behaviors, challenging previous interpretations of such signatures.

Contribution

It introduces a controllable four-terminal Josephson junction with nonlocal effects and shows that similar signatures can arise without true multiterminal hybridization.

Findings

Nonlocal Josephson effect observed with phase-dependent current relations.

Each pair acts as a $$-junction with tunable phase offset.

Array behavior mimics multiterminal junction features.

Abstract

We study a phase-tunable four-terminal Josephson junction formed in an InSbAs two-dimensional electron gas proximitized by aluminum. By embedding the two pairs of junction terminals in asymmetric DC SQUIDs we can control the superconducting phase difference across each pair, thereby gaining information about their current-phase relation. Using a current-bias line to locally control the magnetic flux through one SQUID, we measure a nonlocal Josephson effect, whereby the current-phase relation across two terminals in the junction is strongly dependent on the superconducting phase difference across two completely different terminals. In particular, each pair behaves as a $\phi_0$-junction with a phase offset tuned by the phase difference across the other junction terminals. Lastly, we demonstrate that the behavior of an array of two-terminal junctions replicates most features of the current-phase relation of different multiterminal junctions. This highlights that these signatures alone are not sufficient evidence of true multiterminal Josephson effects arising from hybridization of Andreev bound states in the junction.