Non-contact Andreev reflection as a direct probe of superconductivity on the atomic scale

Wonhee Ko; Jose L. Lado; Petro Maksymovych

doi:10.1021/acs.nanolett.2c00697

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arXiv · 2202.02159

Non-contact Andreev reflection as a direct probe of superconductivity on the atomic scale

Wonhee Ko·Jose L. Lado·Petro Maksymovych

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Abstract

Direct detection of superconductivity has long been a key strength of point-contact Andreev reflection. However, its applicability to atomic-scale imaging is limited by the mechanical contact of the Andreev probe. To this end, we present a new method to probe Andreev reflection in a tunnel junction, leveraging tunneling spectroscopy and junction tunability to achieve quantitative detection of Andreev scattering. This method enables unambiguous assignment of superconducting origins of current-carrying excitations as well as detection of higher order Andreev processes in atomic-scale junctions. We furthermore revealed distinct sensitivity of Andreev reflection to natural defects, such as step edges, even in classical superconductors. The methodology opens a new path to nanoand atomic-scale imaging of superconducting properties, including disordered superconductors and proximity to phase transitions.

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Wonhee Ko, Jose L. Lado, Petro Maksymovych. 2022-02-04. Non-contact Andreev reflection as a direct probe of superconductivity on the atomic scale. https://doi.org/10.1021/acs.nanolett.2c00697

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