Better explicating the strengths and shortcomings of these models will help refine projections and improve transparency in the years ahead.
Image credit: Witsawat.S.
Edited by Eduardo Fradkin, University of Illinois at Urbana–Champaign, Urbana, IL, and approved May 21, 2018 (received for review January 2, 2018)
Significance
In this work we present detailed studies of a nondissipative current, called “quartet supercurrent,” where two distinct Cooper pairs, originating in different terminals, recombine into a four-electron quasiparticle: a quartet. Employing conductance measurements and highly sensitive cross-correlation of current fluctuation, we identified the existence of such a coherent nonlocal state.
Abstract
A novel nonlocal supercurrent, carried by quartets, each consisting of four electrons, is expected to appear in a voltage-biased three-terminal Josephson junction. This supercurrent results from a nonlocal Andreev bound state (ABS), formed among three superconducting terminals. While in a two-terminal Josephson junction the usual ABS, and thus the dc Josephson current, exists only in equilibrium, the ABS, which gives rise to the quartet supercurrent, persists in the nonlinear regime. In this work, we report such resonance in a highly coherent three-terminal Josephson junction made in an InAs nanowire in proximity to an aluminum superconductor. In addition to nonlocal conductance measurements, cross-correlation measurements of current fluctuations provided a distinctive signature of the quartet supercurrent. Multiple device geometries had been tested, allowing us to rule out competing mechanisms and to establish the underlying microscopic origin of this coherent nondissipative current.
Footnotes
↵1Y.C. and Y.R. contributed equally to this work.
- ↵2To whom correspondence should be addressed. Email: Moty.Heiblum{at}weizmann.ac.il.
Author contributions: Y.C., Y.R., M.H., and H.S. designed research; Y.C., Y.R., J.-H.K., M.H., D.F., R.M., and H.S. performed research; Y.C., Y.R., M.H., D.F., and R.M. contributed new reagents/analytic tools; Y.C., Y.R., D.F., and R.M. analyzed data; and Y.C., Y.R., M.H., D.F., R.M., and H.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1800044115/-/DCSupplemental.
Published under the PNAS license.
Nonlocal supercurrent of quartets in a three-terminal Josephson junction
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