Fingerprinting Superconductors by Disentangling Andreev and Quasiparticle Currents Across Tunable Tunnel Junctions

Maksymovych, Petro [Clemson University]; Song, Sang [ORNL] (ORCID:0000000258109944); Lawrie, Benjamin [ORNL] (ORCID:000000031431066X); Ko, Wonhee [University of Tennessee, Knoxville (UTK)]; Lado, Jose [Aalto University, Finland]

doi:10.1002/smll.75379

DOE OSTI · 3740782

Fingerprinting Superconductors by Disentangling Andreev and Quasiparticle Currents Across Tunable Tunnel Junctions

Maksymovych, Petro [Clemson University]·Song, Sang [ORNL] (ORCID:0000000258109944)·Lawrie, Benjamin [ORNL] (ORCID:000000031431066X)·Ko, Wonhee [University of Tennessee, Knoxville (UTK)]·Lado, Jose [Aalto University, Finland]

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Abstract

Tunneling Andreev reflection (TAR) spectroscopy provides a new approach to identify superconducting pairing symmetry at the atomic scale. Using atomistic superconducting transport simulations, we reveal the mechanism by which TAR can distinguish between pairing symmetries, which is complementary to traditional conductance-based techniques. In particular, owing to the additivity of the excess tunneling decay rate, the TAR spectrum is a weighted average of the contributions from quasiparticle currents, Andreev reflection, and higher-order scattering processes, and their relative weights depend on both the superconducting order parameter and the coupling strength. Within the local tunneling model, TAR dominates mid-gap conductance for s-wave superconductors, is suppressed for d-wave, and coexists with quasiparticle tunneling in sign-changing symmetries if the expectation value for the superconducting gap remains finite. Meanwhile, higher-order processes generally enhance the TAR signal when GN exceeds approximately 0.1G0. As a result, TAR provides a rich spectral fingerprint of the underlying pairing symmetry and electronic structure, enabling atomically resolved identification of unconventional superconducting states.

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Maksymovych, Petro [Clemson University], Song, Sang [ORNL] (ORCID:0000000258109944), Lawrie, Benjamin [ORNL] (ORCID:000000031431066X), Ko, Wonhee [University of Tennessee, Knoxville (UTK)], Lado, Jose [Aalto University, Finland]. 2026-09-01. Fingerprinting Superconductors by Disentangling Andreev and Quasiparticle Currents Across Tunable Tunnel Junctions. https://doi.org/10.1002/smll.75379

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