Premature switching in graphene Josephson transistors

Abstract

We investigate electronic transport in single layer graphene coupled to superconducting electrodes. In these Josephson transistors, we observe significant suppression in the critical current I c and large variation in the product I c R n in comparison to theoretic predictions in the ballistic limit. We show that the depression of I c can be explained by premature switching in underdamped Josephson junctions described within the resistively and capacitively shunted junction (RCSJ) model. By considering the effect of premature switching and dissipation, the calculated gate dependence of product I c R n agrees with experimental data. Our discovery underscores the crucial role of thermal fluctuations in electronic transport in graphene Josephson transistors.

Ballistic-like supercurrent in suspended graphene Josephson weak links

“…We notice that the superconducting gap (2D B1 meV) appears to be rather strongly suppressed compared with the estimation from the transition temperature (D(0) ¼ 1.764 k B , T c B1.8 meV). The gap reduction had been previously observed in Josephson weak links, including graphenebased Josephson weak links 17 . Pd appears to have significant effect in reducing the gap size 18 .…”

“…For a critical current of B100 nA, this gives GB1. It has been demonstrated in diffusive graphene Josephson weak links at millikelvin temperatures (when Go o1) that the supercurrent is reduced through a premature switching process 3,17,27 . For stronger thermal fluctuation, however, phase diffusion dominates and causes a finite voltage in the supercurrent regime as well as gradual switching 28,29 .…”

Effect of thick barrier in a gapped graphene Josephson junction

“…In this work, we investigate the Josephson current in a gapped graphene-based superconductor/barrier/superconductor (S/I/S) junction. The fabrication of superconductor on graphene is created by contacting the superconducting electrodes as mostly using aluminum (Al) electrodes [8][9][10]. The Josephson effect in graphene-based junction is observed in the Dirac fermionic behavior through a gate control [11][12].…”

“…The Josephson effect in graphene-based junction is observed in the Dirac fermionic behavior through a gate control [11][12]. The gate-tunable effect can be indicated to the switching current and is led to the application of superconducting electronic devices [10,12]. We concentrate on the gate-tunable supercurrent under the effect of thick barrier limit.…”

Phase dynamics in graphene-based Josephson junctions in the presence of thermal and correlated fluctuations

“…Specifically, in Ref. [16] the reduction of the critical current and variations in the product I C R N were experimentally observed and theoretically explained considering non-negligible the thermal fluctuations. Other authors 3,17 suggested a supercurrent reduction by premature switching induced by thermal and electromagnetic noise.…”