Zero Crossing Steps and Anomalous Shapiro Maps in Graphene Josephson Junctions

Abstract

The AC Josephson effect manifests itself in the form of "Shapiro steps" of quantized voltage in Josephson junctions subject to radiofrequency (RF) radiation. This effect presents an early example of a driven−dissipative quantum phenomenon and is presently utilized in primary voltage standards. Shapiro steps have also become one of the standard tools to probe junctions made in a variety of novel materials. Here we study Shapiro steps in a widely tunable graphene-based Josephson junction in which the highfrequency dynamics is determined by the on-chip environment. We investigate the variety of patterns that can be obtained in this well-understood system depending on the carrier density, temperature, RF frequency, and magnetic field. Although the patterns of Shapiro steps can change drastically when just one parameter is varied, the overall trends can be understood and the behaviors straightforwardly simulated, showing some key differences from the conventional RCSJ model. The resulting understanding may help interpret similar measurements in more complex materials.

Phase locking and noise driven dynamics in a Josephson junction electronic analog

“…The resulting I-V curves were then numerically differentiated so that voltage plateaus result in dark blue regions of vanishing R, while yellow boundaries correspond to transitions between plateaus. The map bears a striking similarity to the patterns observed in conventional over- damped Josephson junction under microwave radiation [24].…”

Multiterminal Inverse AC Josephson Effect

“…Instead, we choose to empirically apply 10's of nA of current noise to our device. This level is similar to the amount of noise applied while modeling similar two-terminal junctions [47].…”

Description of Shapiro steps on the potential energy surface of a Frenkel–Kontorova model Part I: The chain in a variable box

“…Thus, the frequency, as well as the average velocity of the chain, are locked. There emerge Shapiro steps which one can compare with experimental results [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15].…”

“…Shapiro steps are reported in the observation of different experiments [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. We concentrate here on the emergence of such steps in calculations with the FK model with periodic boundary conditions (PBC) [16][17][18][19][20].…”