SEM image of three-terminal junctions fabricated in graphene with molybdenum-rhenium contacts
Bias-bias map where each step corresponds to an increase in applied RF power, leading to the emergence of Shapiro steps
This standard map demonstrates three supercurrent branches corresponding to supercurrents mediated between each pair of contacts
Multi-terminal Josephson junctions have emerged as a promising platform touching upon a broad array of physical phenomena such as nonlinear/chaotic dynamics, integrated quantum circuit elements, and synthetic topological materials. Indeed, the added complexity of three or more coherent superconducting contacts results in emergent states inaccessible in the constituent junctions.
Our group was the first to study graphene multiterminal junctions where it was found that both dissipative currents and supercurrents can coexist in the same region of graphene. This work was continued by characterizing the multiterminal inverse AC Josephson effect, where the higher dimensionality of the energy-phase landscape gave rise to unexpected fractional Shapiro steps. Most recently, it was discovered that coherent 4 (or more) electron transport can emerge in these devices – generating a robust cos(2\phi) energy dependence, which may be used to create topologically protected qubits.
Josephson circuits
SEM image of a Josephson circuit with a superconducting island connecting the three superconducting leads
Bias-bias map highlighting the multiplet (here, quartet and nulltet) supercurrents arising from dynamical effects in the circuit
Bias-bias map focusing on one nulltet branch--supercurrent between L and R while both junctions are biased above their critical currents
Schematic based on our understanding of the quartet and nulltet mechanisms. Note the lack of Cooper pairs ending on the island in the nulltet phase, hence our choice of name
I-V curves demonstrating our ability to tune the diode from ~100% efficiency for positive currents, through 0% efficiency where positive and negative critical currents are balanced, and to ~100% efficiency for negative currents
We have additionally modified these structures to study the collective dynamics of a several junctions in a single device. These Josephson circuits are theorized to provide a complimentary approach towards engineering complex phase dynamics and measuring the corresponding rich physical phenomena. We fabricated and studied a Josephson circuit and discovered multiplet supercurrents arising from dynamical phase locking between superconducting contacts (Arnault et al., 2024). We have also explored engineering superconducting devices in these systems, including creating a 100% efficiency superconducting diode at zero magnetic field (Chiles et al., 2023).
Corresponding grad student: Johnny Chiles (john.chiles@duke.edu)
Related Publications
Multiplet Supercurrents in a Josephson Circuit.
E. G. Arnault, J. Chiles, T. F. Q. Larson, C. Chen, L. Zhao, K. Watanabe, T. Taniguchi, F. Amet, and G. Finkelstein
arXiv (2024)
Nonreciprocal Supercurrents in a Field-Free Graphene Josephson Triode.
J. Chiles, E. G. Arnault, C. Chen, T. F. Q. Larson, L. Zhao, K. Watanabe, T. Taniguchi, F. Amet, and G. Finkelstein
Nano Letters (2023)
Noise-Induced Stabilization of Dynamical States With Broken Time-Reversal Symmetry.
T. F. Q. Larson, L. Zhao, E. G. Arnault, M. Wei, A. Seredinski, H. Li, K. Watanabe, T. Taniguchi, F. Amet, and G. Finkelstein
arXiv (2022)
Dynamical Stabilization of Multiplet Supercurrents in Multi-terminal Josephson Junctions.
E. G. Arnault, S. Idris, A. McConnell, L. Zhao, T. F. Q. Larson, K. Watanabe, T. Taniguchi, G. Finkelstein, and F. Amet
Nano Letters (2022)
The Multi-terminal Inverse AC Josephson Effect.
E. G. Arnault, T. F. Q. Larson, A. Seredinski, L. Zhao, H. Li, K. Watanabe, T. Taniguchi, I. V. Borzenets, F. Amet, and G. Finkelstein.
Nano Letters (2021)
Supercurrent Flow in Multiterminal Graphene Josephson Junctions
A. W. Draelos, M. T. Wei, A. Seredinski, H. Li, Y. Mehta, K. Watanabe, T. Taniguchi, I. V. Borzenets, F. Amet, G. Finkelstein
Nano Letters (2019)
