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Shape-Resonant Superconductivity in Nanofilms: from Weak to Strong Coupling

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Abstract

Ultrathin superconductors of different materials are becoming a powerful platform to find mechanisms for enhancement of superconductivity, exploiting shape resonances in different superconducting properties. Here, we evaluate the superconducting gap and its spatial profile, the multiple gap components, and the chemical potential, of generic superconducting nanofilms, considering the pairing attraction and its energy scale as tunable parameters, from weak to strong coupling, at fixed electron density. Superconducting properties are evaluated at mean field level as a function of the thickness of the nanofilm, in order to characterize the shape resonances in the superconducting gap. We find that the most pronounced shape resonances are generated for weakly coupled superconductors, while approaching the strong coupling regime the shape resonances are rounded by a mixing of the subbands due to the large energy gaps extending over large energy scales. Finally, we find that the spatial profile, transverse to the nanofilm, of the superconducting gap acquires a flat behavior in the shape resonance region, indicating that a robust and uniform multigap superconducting state can arise at resonance.

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Acknowledgments

We acknowledge D. Valentinis, D. Van der Marel, and C. Berthod for useful discussions. A. Ricci is also acknowledged for his comments on the experimental detection of the predictions of this paper. A. Bianconi acknowledges financial support from Superstripes non-profit organization. M. Cariglia acknowledges CNPq support from project (205029 / 2014-0) and FAPEMIG support from project APQ-02164-14. M.M. Doria acknowledges CNPq support from funding (23079.014992 / 2015-39). M.V. Milošević acknowledges support from Research Foundation - Flanders (FWO). A. Perali acknowledges financial support from the University of Camerino under the project FAR “Control and enhancement of superconductivity by engineering materials at the nanoscale”. All authors acknowledge the collaboration within the MultiSuper Network (http://www.multisuper.org) for exchange of ideas and suggestions.

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Authors and Affiliations

  1. Departamento de Física, Universidade Federal de Ouro Preto, 35400-000, Ouro Preto, Minas Gerais, Brazil

    Marco Cariglia

  2. School of Pharmacy, Physics Unit, University of Camerino, 62032, Camerino, Italy

    Marco Cariglia, Alfredo Vargas-Paredes, Mauro M. Doria & Andrea Perali

  3. Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, 2020, Antwerpen, Belgium

    Alfredo Vargas-Paredes & Milorad V. Milošević

  4. Instituto de Física, Universidade Federal do Rio de Janeiro, 21941-972, Rio de Janeiro, Brazil

    Mauro M. Doria

  5. Rome International Center for Materials Science Superstripes (RICMASS), Via dei Sabelli 119A, 00185, Rome, Italy

    Antonio Bianconi

  6. INFN Sezione di Perugia, Perugia, Italy

    Andrea Perali

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  1. Marco Cariglia
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  2. Alfredo Vargas-Paredes
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  6. Andrea Perali
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Correspondence to Andrea Perali.

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Cariglia, M., Vargas-Paredes, A., Doria, M.M. et al. Shape-Resonant Superconductivity in Nanofilms: from Weak to Strong Coupling. J Supercond Nov Magn 29, 3081–3086 (2016). https://doi.org/10.1007/s10948-016-3673-1

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  • DOI: https://doi.org/10.1007/s10948-016-3673-1

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