Superconductive coupling in tailored [(SnSe)1+δ]m(NbSe2)1 multilayers

M. Trahms1,4, C. Grosse1,5, M.B. Alemayehu2, O.K. Hite2, O. Chiatti1, A. Mogilatenko1,3, D.C. Johnson2 and S.F. Fischer1

Published in:

Supercond. Sci. Technol., vol. 31, no. 6, pp. 065006 (2018).

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Abstract:

Ferecrystals are a new artificially layered material system, in which the individual layers are stacked with monolayer precision and are turbostratically disordered. Here, the superconducting coupling of the NbSe2 layers in [(SnSe)1+δ]m[NbSe2]1 ferecrystals with m between 1 and 6 are investigated. The variation of m effectively increases the distance between the superconducting NbSe2 monolayers. We find a systematic decrease of the transition temperature with an increasing number of SnSe layers per repeat unit. For m = 9 a superconducting transition can no longer be observed at temperatures above 250 mK. In order to investigate the superconducting coupling between individual NbSe2 layers, the cross-plane Ginzburg-Landau coherence lengths were determined. Electric transport measurements of the superconducting transition were performed in the presence of a magnetic field, oriented parallel and perpendicular to the layers, at temperatures closely below the transition temperature. A decoupling with increasing distance of the NbSe2 layers is observed. However, ferecrystals with NbSe2 layers separated by up to six layers of SnSe are still considered as three-dimensional superconductors.

1 Novel Materials Group, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
2 Department of Chemistry and Materials Science Institute, University of Oregon, Eugene, OR 97403, United States of America
3 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, 12489 Berlin, Germany
4 Present affiliation: Helmholtz-Zentrum Berlin, Kekulestr.5, 12489 Berlin, Germany
5 Present affiliation: Berliner Nanotest und Design GmbH, Volmerstr. 9B, 12489 Berlin

Keywords:

superconducting thinfilms, Ginzburg-Landau coherence lengths, superconductor-semiconductor hybrid layers, transition temperatures, coupling