Superconductivity in medium- and high-entropy alloy thin films: Impact of thickness and external pressure

Gabriel Pristas, Julius Backai, Matus Orendac, Slavomir Gabani, Filip Kosuth, Marek Kuzmiak, Pavol Szabo, Emil Gazo, Robert Franz, Sabrina Hirn, Georg Gruber, Christian Mitterer, Serhii Vorobiov, Karol Flachbart

Publikation: Beitrag in FachzeitschriftArtikelForschungBegutachtung


We have prepared and investigated superconducting Nb67Hf11Ti11Zr11 and Nb35Ta35Hf10Ti10Zr10 medium- and high-entropy alloys in form of thin films with thicknesses of 600, 100, and 30 nm, and compared their properties with bulk counterparts. We show that the superconducting transition temperature Tc as well as the upper critical magnetic field Bc2(0) decrease with decreasing thickness. Application of hydrostatic pressure up to 33 kbar on the 600-nm Nb35Ta35Hf10Ti10Zr10 film shows a decrease of Tc with pressure, which differs from that observed on bulk sample. However, no clear Tc dependence was observed if pressure was applied on the 100-nm film. This result is most likely related to increasing disorder (tendency to structure amorphization) in thinner films. Moreover, we performed point-contact spectroscopy measurements on the 600-nm Nb67Hf11Ti11Zr11 and Nb35Ta35Hf10Ti10Zr10 films and were able to observe directly the temperature development of the superconducting energy gap Δ(T) and determine the superconducting coupling strength 2Δ/kBTc=3.54 and 2Δ/kBTc=4.21, respectively, which is consistent with that of conventional s-wave phonon-mediated Bardeen-Cooper-Schrieffer superconductors.

FachzeitschriftPhysical review : B, Condensed matter and materials physics
PublikationsstatusVeröffentlicht - 17 Jan. 2023

Bibliographische Notiz

Funding Information:
This work was supported by projects Mobility SK-AT, by the Slovak Research and Development Agency under the Contracts No. APVV-18-0358, No. VEGA 2/0032/20, and No. VA SR ITMS2014+ 313011W856, and by the European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement No. 824109 (European Microkelvin Platform). Liquid nitrogen for experiments was sponsored by U.S. Steel Košice, s.r.o.

Publisher Copyright:
© 2023 American Physical Society.

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