Overdamped Phase Diffusion in hBN Encapsulated Graphene Josephson Junctions

TL;DR

This study explores the phase diffusion behavior in hBN-encapsulated graphene Josephson junctions, revealing overdamped dynamics in a regime typically dominated by underdamped behavior, with implications for quantum device design.

Contribution

It demonstrates that graphene Josephson junctions can exhibit overdamped phase diffusion, contrasting with the common underdamped behavior in similar systems.

Findings

Junctions are non-hysteretic down to 2.7K

Resistance scales with temperature via phase diffusion

Overdamped behavior confirmed by carrier concentration variation

Abstract

We investigate the zero-bias behavior of Josephson junctions made of encapsulated graphene boron nitride heterostructures in the long ballistic junction regime. For temperatures down to 2.7K, the junctions appear non-hysteretic with respect to the switching and retrapping currents $I_C$ and $I_R$. A small non-zero resistance is observed even around zero bias current, and scales with temperature as dictated by the phase diffusion mechanism. By varying the graphene carrier concentration we are able to confirm that the observed phase diffusion mechanism follows the trend for an overdamped Josephson junction. This is in contrast with the majority of graphene-based junctions which are underdamped and shorted by the environment at high frequencies.