Andreev reflection spectroscopy in strongly paired superconductors
Abstract
Motivated by recent experiments on low-carrier-density superconductors, including twisted multilayer graphene, we study signatures of the BCS-to-BEC evolution in Andreev reflection spectroscopy. We establish that in a standard quantum point contact geometry, Andreev reflection in a BEC superconductor is unable to mediate a zero-bias conductance beyond e²/h per lead channel. This bound is shown to result from a mapping that links the subgap conductance of BCS and BEC superconductors. We then demonstrate that sharp signatures of BEC superconductivity, including perfect Andreev reflection, can be recovered by tunneling through a suitably designed potential well. We propose various tunneling spectroscopy setups to experimentally probe this recovery.
Additional Information
© 2023 American Physical Society. We thank Mohit Randeria, Hyunjin Kim, Michał Papaj, and Kevin Nuckolls for insightful discussions. This work was supported by the Gordon and Betty Moore Foundation's EPiQS Initiative, Grant No. GBMF8682 (C.L. and É.L.-H.); the U.S. Army Research Office under Grant Award No. W911NF-17-1-0323 (J.A.); the Caltech Institute for Quantum Information and Matter, an NSF Physics Frontiers Center with support of the Gordon and Betty Moore Foundation through Grant No. GBMF1250 (J.A. and S.N.-P.); the NSF Career programme (DMR-1753306) (S.N.-P.); and the Walter Burke Institute for Theoretical Physics at Caltech (A.T. and J.A.).Attached Files
Published - PhysRevB.107.L020502.pdf
Supplemental Material - AndreevBCSBEC_Supplement.pdf
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Additional details
- Eprint ID
- 121496
- Resolver ID
- CaltechAUTHORS:20230523-599406900.1
- GBMF8682
- Gordon and Betty Moore Foundation
- W911NF-17-1-0323
- Army Research Office (ARO)
- Institute for Quantum Information and Matter (IQIM)
- GBMF1250
- Gordon and Betty Moore Foundation
- DMR-1753306
- NSF
- Walter Burke Institute for Theoretical Physics, Caltech
- Created
-
2023-06-21Created from EPrint's datestamp field
- Updated
-
2023-06-21Created from EPrint's last_modified field
- Caltech groups
- Institute for Quantum Information and Matter, Walter Burke Institute for Theoretical Physics