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Spectroscopic evidence for strong correlations between local superconducting gap and local Altshuler-Aronov density of states suppression in ultrathin NbN films

Carbillet, C.; Cherkez, V.; Skvortsov, M. A.; Feigel'man, M. V.; Debontridder, F.; Ioffe, L. B.; Stolyarov, V. S.; Ilin, K.; Siegel, M.; Noûs, C.; Roditchev, D.; Cren, T.; Brun, C.

Disorder has different profound effects on superconducting thin films. For a large variety of materials, increasing disorder reduces electronic screening which enhances electron-electron repulsion. These fermionic effects lead to a mechanism described by Finkelstein: when disorder combined to electron-electron interactions increases, there is a global decrease of the superconducting energy gap Δ and of the critical temperature T$_{c}$, the ratio Δ/kBT$_{c}$ remaining roughly constant. In addition, in most films an emergent granularity develops with increasing disorder and results in the formation of inhomogeneous superconducting puddles. These gap inhomogeneities are usually accompanied by the development of bosonic features: a pseudogap develops above the critical temperature T$_{c}$ and the energy gap Δ starts decoupling from T$_{c}$. Thus the mechanism(s) driving the appearance of these gap inhomogeneities could result from a complicated interplay between fermionic and bosonic effects. By studying the local electronic properties of a NbN film with scanning tunneling spectroscopy (STS) we show that the inhomogeneous spatial distribution of Δ is locally strongly correlated to a large depletion in the local density of states (LDOS) around the Fermi level, associated to the Altshuler-Aronov effect induced by strong electronic interactions. ... mehr

Zugehörige Institution(en) am KIT Institut für Mikro- und Nanoelektronische Systeme (IMS)
Publikationstyp Forschungsbericht/Preprint
Publikationsjahr 2020
Sprache Englisch
Identifikator KITopen-ID: 1000123542
Umfang 11 S.
Vorab online veröffentlicht am 02.07.2020
Nachgewiesen in arXiv
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