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TT: Fachverband Tiefe Temperaturen

TT 21: Focus Session: Strongly Disordered Superconductors

TT 21.5: Invited Talk

Tuesday, March 19, 2024, 11:45–12:15, H 0104

Spectral Gap and Order Parameter Statistics in Disordered Superconducting Films — •Matthias Stosiek — Department of Applied Physics, Aalto University, Finland

The interplay of disorder and superconductivity leads to a rich variety of phenomena like the development of superconducting islands at superconductor-insulator transitions or an enhancement of the superconducting critical temperature.

These phenomena are enabled by the local fluctuations of superconducting observables. In particular, two observables are of outstanding interest: the superconducting order parameter and the spectral gap of the local density of states. While identical in absolute value in BCS theory, these observables can differ dramatically in dirty superconductors. In many previous studies, this difference was assumed to be negligible in the weakly disordered regime.

In the here presented work, we aim to elucidate this assumption. For this, we conducted a computational study of disordered thin-film superconductors within fully self-consistent mean-field theory. To produce our results, we employed a self-written, highly optimized self-consistency solver [1] that we made publicly available [2]. Our results include: (i) demonstration of only small correlations between the two observables even in the weakly disordered regime; (ii) indications of a non-local relation between order parameter and spectral gap.

[1] M. Stosiek, B. Lang, F. Evers, Phys. Rev. B 101 (2020) 144503

[2] https://github.com/ccmt-regensburg/self_ consistency_ solver

Keywords: Superconductivity; Mean-Field Theory; Self-Consistency; Disorder; Local Density of States