Atomic-Scale Andreev Probe of Unconventional Superconductivity

Wonhee Ko; Sang Yong Song; Jiaqiang Yan; Jose L. Lado; Petro Maksymovych

doi:10.1021/acs.nanolett.3c02658

Atomic-Scale Andreev Probe of Unconventional Superconductivity

Wonhee Ko, Sang Yong Song, Jiaqiang Yan, Jose L. Lado, Petro Maksymovych

Research output: Contribution to journal › Article › peer-review

Abstract

Recent emergence of low-dimensional unconventional superconductors and their exotic interface properties calls for new approaches to probe the pairing symmetry, a fundamental and frequently elusive property of the superconducting condensate. Here, we introduce the unique capability of tunneling Andreev reflection (TAR) to probe unconventional pairing symmetry, utilizing the sensitivity of this technique to specific Andreev reflections. Specifically, suppression of the lowest-order Andreev reflection due to quantum interference but emergence of the higher-order Andreev processes provides direct evidence of the sign-changing order parameter in the paradigmatic FeSe superconductor. TAR spectroscopy also reveals two superconducting gaps, points to a possibility of a nodal gap structure, and directly confirms that superconductivity is locally suppressed along the nematic twin boundary, with preferential and near-complete suppression of the larger energy gap. Our findings therefore enable new, atomic-scale insight into microscopic, inhomogeneous, and interfacial properties of emerging quantum materials.

Original language	English
Pages (from-to)	8310-8318
Number of pages	9
Journal	Nano Letters
Volume	23
Issue number	17
DOIs	https://doi.org/10.1021/acs.nanolett.3c02658
State	Published - Sep 13 2023

Funding

Experimental measurements were supported by the U.S. Department of Energy, Office of Science, Materials Sciences and Engineering Division (W.K., P.M.). Experiments were carried out as part of the user project at the Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, which is a U.S. Department of Energy Office of Science User Facility. J.L.L. acknowledges the computational resources provided by the Aalto Science-IT project and the financial support from the Academy of Finland Project No. 331342 and No. 336243 and the Jane and Aatos Erkko Foundation.

Funders	Funder number
U.S. Department of Energy
Office of Science
Oak Ridge National Laboratory
Division of Materials Sciences and Engineering
Academy of Finland	336243, 331342
Jane ja Aatos Erkon Säätiö

Keywords

Andreev reflection
quantum interference
sign-changing gap
tunneling
unconventional superconductivity

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10.1021/acs.nanolett.3c02658

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title = "Atomic-Scale Andreev Probe of Unconventional Superconductivity",

abstract = "Recent emergence of low-dimensional unconventional superconductors and their exotic interface properties calls for new approaches to probe the pairing symmetry, a fundamental and frequently elusive property of the superconducting condensate. Here, we introduce the unique capability of tunneling Andreev reflection (TAR) to probe unconventional pairing symmetry, utilizing the sensitivity of this technique to specific Andreev reflections. Specifically, suppression of the lowest-order Andreev reflection due to quantum interference but emergence of the higher-order Andreev processes provides direct evidence of the sign-changing order parameter in the paradigmatic FeSe superconductor. TAR spectroscopy also reveals two superconducting gaps, points to a possibility of a nodal gap structure, and directly confirms that superconductivity is locally suppressed along the nematic twin boundary, with preferential and near-complete suppression of the larger energy gap. Our findings therefore enable new, atomic-scale insight into microscopic, inhomogeneous, and interfacial properties of emerging quantum materials.",

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AU - Maksymovych, Petro

PY - 2023/9/13

Y1 - 2023/9/13

N2 - Recent emergence of low-dimensional unconventional superconductors and their exotic interface properties calls for new approaches to probe the pairing symmetry, a fundamental and frequently elusive property of the superconducting condensate. Here, we introduce the unique capability of tunneling Andreev reflection (TAR) to probe unconventional pairing symmetry, utilizing the sensitivity of this technique to specific Andreev reflections. Specifically, suppression of the lowest-order Andreev reflection due to quantum interference but emergence of the higher-order Andreev processes provides direct evidence of the sign-changing order parameter in the paradigmatic FeSe superconductor. TAR spectroscopy also reveals two superconducting gaps, points to a possibility of a nodal gap structure, and directly confirms that superconductivity is locally suppressed along the nematic twin boundary, with preferential and near-complete suppression of the larger energy gap. Our findings therefore enable new, atomic-scale insight into microscopic, inhomogeneous, and interfacial properties of emerging quantum materials.

AB - Recent emergence of low-dimensional unconventional superconductors and their exotic interface properties calls for new approaches to probe the pairing symmetry, a fundamental and frequently elusive property of the superconducting condensate. Here, we introduce the unique capability of tunneling Andreev reflection (TAR) to probe unconventional pairing symmetry, utilizing the sensitivity of this technique to specific Andreev reflections. Specifically, suppression of the lowest-order Andreev reflection due to quantum interference but emergence of the higher-order Andreev processes provides direct evidence of the sign-changing order parameter in the paradigmatic FeSe superconductor. TAR spectroscopy also reveals two superconducting gaps, points to a possibility of a nodal gap structure, and directly confirms that superconductivity is locally suppressed along the nematic twin boundary, with preferential and near-complete suppression of the larger energy gap. Our findings therefore enable new, atomic-scale insight into microscopic, inhomogeneous, and interfacial properties of emerging quantum materials.

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Atomic-Scale Andreev Probe of Unconventional Superconductivity

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