On the origin of in-gap states in homogeneously disordered ultrathin films. MoC case

Many disordered superconducting films exhibit smeared tunneling spectra with evident in-gap states. We demonstrated that the tunneling density of states in ultrathin MoC films is gapless and can be described by the Dynes version of the BCS density of states with a strong broadening parameter Gamma a...

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Bibliographic Details
Published in:arXiv.org 2018-09
Main Authors: Hašková, V, Kopčík, M, Szabó, P, Samuely, T, Kačmarčík, J, Onufriienko, O, Žemlička, M, Neilinger, P, Grajcar, M, Samuely, P
Format: Article
Language:English
Subjects:
Breaking
Density of states
Energy dissipation
Energy gap
Sapphire
Silicon substrates
Superconducting films
Superconductivity
Thickness
Thin films
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Summary:Many disordered superconducting films exhibit smeared tunneling spectra with evident in-gap states. We demonstrated that the tunneling density of states in ultrathin MoC films is gapless and can be described by the Dynes version of the BCS density of states with a strong broadening parameter Gamma accounting for the suppression of coherence peaks and increased in-gap states. The thinner the film, the lower the Tc and the superconducting energy gap Delta and the larger the Gamma. MoC films of 3 nm thickness deposited simultaneously on silicon and sapphire substrates reveal very similar scalar disorder, evidenced by the equal sheet resistance, but exhibit different superconducting characteristics of Tc, Delta and Gamma, suggesting that pair breaking responsible for the dissipation channel and the suppression of superconductivity originates on the film-substrate interface. It indicates that sapphire is a stronger pair breaker. Interface pair breaking can be operative in other cases as well.
ISSN:2331-8422
DOI:10.48550/arxiv.1809.00849