Anomalous Phase Dynamics of Driven Graphene Josephson Junctions

TL;DR

This paper investigates the nonlinear phase dynamics in graphene Josephson junctions, revealing bistability and chaotic behavior influenced by the current-phase relation, with implications for topological and exotic physics research.

Contribution

It presents the first observation of bistability and chaotic phase dynamics in graphene Josephson junctions, linking nonlinear dynamical phenomena to condensed matter physics.

Findings

Observation of phase-locked Shapiro steps under RF radiation

Detection of bistability with seconds-scale switching times

Correlation of chaotic behavior with current-phase relation sensitivity

Abstract

Josephson junctions with weak-links of exotic materials allow the elucidation of the Josephson effect in previously unexplored regimes. Further, such devices offer a direct probe of novel material properties, for example in the search for Majorana fermions. In this work, we report on DC and AC Josephson effect of high-mobility, hexagonal boron nitride (h-BN) encapsulated graphene Josephson junctions. On the application of RF radiation, we measure phase-locked Shapiro steps. An unexpected bistability between $\pm 1$ steps is observed with switching times on the order of seconds. A critical scaling of a bistable state is measured directly from the switching time, allowing for direct comparison to numerical simulations. We show such intermittent chaotic behavior is a consequence of the nonlinear dynamics of the junction and has a sensitive dependence on the current-phase relation. This work draws connections between nonlinear phenomena in dynamical systems and their implications for ongoing condensed matter experiments exploring topology and exotic physics.