Revisiting the adiabatic limit in ballistic multiterminal Josephson junctions

TL;DR

This paper investigates the behavior of multiterminal Josephson junctions at high bias voltages, proposing a model that explains mesoscopic oscillations of the critical current influenced by quantum correlations and nonequilibrium effects.

Contribution

It introduces a new model for large-scale MJJs under high bias, connecting adiabatic approximation with Floquet--Kulik levels and predicting voltage scales for critical current oscillations.

Findings

Quantum-correlated pairs are inversely proportional to the number of channels.

The model predicts characteristic voltage scales for mesoscopic oscillations.

The approach links experimental observations across quartets, topology, and Floquet theory.

Abstract

Motivated by recent experiments on multiterminal Josephson junctions (MJJs) that probe different ranges of the size and bias voltage parameters, we explore the regime of increasing bias voltage in large-scale devices, where the electrochemical potential becomes comparable to the 1D energy level spacing. We find that the relative number of quantum-correlated pairs formed by colliding Floquet--Kulik quartet levels is equal to the inverse of the number of channels. This observation motivates a model for the intermediate regime in which the ballistic central two-dimensional normal metal is treated as a continuum under the adiabatic approximation, while Andreev modes propagate in a background of voltage- and flux-tunable nonequilibrium electronic populations. The model predicts characteristic voltage scales that govern the mesoscopic oscillations of the critical current, and these scales are at the crossroads of interpreting experiments in all sectors of the MJJs: quartets, topology, and Floquet theory. Our model is specifically inspired by the recent Harvard and Penn State group experiments.