Current-phase relation of ballistic graphene Josephson junctions

G. Nanda, J.L. Aguilera Servin, P. Rakyta, A. Kormányos, R. Kleiner, D. Koelle, K. Watanabe, T. Taniguchi, L. Vandersypen, S. Goswami, Nano Letters 17 (2017) 3396–3401.

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Abstract
The current-phase relation (CPR) of a Josephson junction (JJ) determines how the supercurrent evolves with the superconducting phase difference across the junction. Knowledge of the CPR is essential in order to understand the response of a JJ to various external parameters. Despite the rising interest in ultraclean encapsulated graphene JJs, the CPR of such junctions remains unknown. Here, we use a fully gate-tunable graphene superconducting quantum intereference device (SQUID) to determine the CPR of ballistic graphene JJs. Each of the two JJs in the SQUID is made with graphene encapsulated in hexagonal boron nitride. By independently controlling the critical current of the JJs, we can operate the SQUID either in a symmetric or asymmetric configuration. The highly asymmetric SQUID allows us to phase-bias one of the JJs and thereby directly obtain its CPR. The CPR is found to be skewed, deviating significantly from a sinusoidal form. The skewness can be tuned with the gate voltage and oscillates in antiphase with Fabry-Pérot resistance oscillations of the ballistic graphene cavity. We compare our experiments with tight-binding calculations that include realistic graphene-superconductor interfaces and find a good qualitative agreement.
Publishing Year
Date Published
2017-05-05
Journal Title
Nano Letters
Volume
17
Issue
6
Page
3396 - 3401
ISSN
IST-REx-ID

Cite this

Nanda G, Aguilera Servin JL, Rakyta P, et al. Current-phase relation of ballistic graphene Josephson junctions. Nano Letters. 2017;17(6):3396-3401. doi:10.1021/acs.nanolett.7b00097
Nanda, G., Aguilera Servin, J. L., Rakyta, P., Kormányos, A., Kleiner, R., Koelle, D., … Goswami, S. (2017). Current-phase relation of ballistic graphene Josephson junctions. Nano Letters, 17(6), 3396–3401. https://doi.org/10.1021/acs.nanolett.7b00097
Nanda, Gaurav, Juan L Aguilera Servin, Péter Rakyta, Andor Kormányos, Reinhold Kleiner, Dieter Koelle, Kazuo Watanabe, Takashi Taniguchi, Lieven Vandersypen, and Srijit Goswami. “Current-Phase Relation of Ballistic Graphene Josephson Junctions.” Nano Letters 17, no. 6 (2017): 3396–3401. https://doi.org/10.1021/acs.nanolett.7b00097.
G. Nanda et al., “Current-phase relation of ballistic graphene Josephson junctions,” Nano Letters, vol. 17, no. 6, pp. 3396–3401, 2017.
Nanda G, Aguilera Servin JL, Rakyta P, Kormányos A, Kleiner R, Koelle D, Watanabe K, Taniguchi T, Vandersypen L, Goswami S. 2017. Current-phase relation of ballistic graphene Josephson junctions. Nano Letters. 17(6), 3396–3401.
Nanda, Gaurav, et al. “Current-Phase Relation of Ballistic Graphene Josephson Junctions.” Nano Letters, vol. 17, no. 6, American Chemical Society, 2017, pp. 3396–401, doi:10.1021/acs.nanolett.7b00097.
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