Abstract
We report a probable observation of the dc Josephson effect in mesoscopic junctions of three and four superconductors. The devices are fabricated in a top-down fashion from a hybrid semiconductor-superconductor epitaxial heterostructure. In general, the critical current of an -terminal junction is an ()-dimensional hypersurface in the space of bias currents, which can be reduced to a set of critical current contours. The geometry of critical current contours exhibits nontrivial responses to electrical gating, magnetic field, and phase bias, and it can be reproduced by the scattering formulation of the Josephson effect generalized to the case of . Besides establishing solid ground beneath a host of recent theory proposals, our experiment accomplishes an important step toward creating trijunctions of topological superconductors, essential for braiding operations.
- Received 19 January 2019
- Accepted 13 July 2020
- Corrected 27 October 2020
DOI:https://doi.org/10.1103/PhysRevX.10.031051
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Corrections
27 October 2020
Correction: A statement of thanks was inadvertently removed from the Acknowledgments section during production and has been restored.
Popular Summary
The realization that a nondissipative current, the supercurrent, can flow from one superconductor to another across a nonsuperconducting junction region won Josephson a Nobel prize. We report the generalization of this Josephson effect to a case where more than two superconductors are connected across a normal conductor. Such multiterminal Josephson junctions have been essential elements in proposals for fault-tolerant quantum computing, simulating band structure of higher-dimensional materials, and creating novel components for superconducting electronics.
In particular, we fabricate three- and four-terminal junctions with submicron dimensions from an epitaxial 2D material that combines an indium arsenide semiconductor with superconducting aluminum. While conventional two-terminal junctions are typically characterized by the response of their critical current to a magnetic field, in our devices multiple supercurrents can simultaneously transit across the junction. We introduce a geometric representation for such a multidimensional supercurrent flow, observe its response to both magnetic and electric fields, and verify the multiterminal Josephson effect through the comparison of our data to an elementary scattering theory model.
Our work initiates an exciting new chapter in mesoscopic superconductivity at intermediate size scales.
