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Tuning superconductivity in high entropy nitrides

Gabriel Pristáš1, Slavomír Gabáni1, Július Bačkai1, Oleksandr Onufriienko1, Lukas Kölbl2, Magdalena Kirchmair2, Christian Mitterer2,*, and Karol Flachbart1,†

  • *Contact author: christian.mitterer@unileoben.ac.at
  • †Contact author: flachb@saske.sk
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Phys. Rev. Materials 10, 064805 – Published 29 June, 2026

DOI: https://doi.org/10.1103/jdhy-4xf5

Abstract

The recently investigated nitrogen (N) incorporation into TiNbMoTaW high entropy alloy films leads to a domelike superconducting transition temperature TC vs nitrogen concentration x (with x=N/M representing the ratio between atomic fractions of nitrogen and metal atoms, M=Ti+Nb+Mo+Ta+W) in the respective high entropy nitride (TiNbMoTaW)1.0Nx, with a large TC enhancement. In this study, we report on the effect of N insertion into NbTaHfTiZr films, which show a lower valence electron concentration and a lower configuration entropy than those of TiNbMoTaW. The TC vs x dependence in (NbTaHfTiZr)1.0Nx exhibits a different course, in which TC first decreases from ∼6.5K at x=0 to TC≈1K at x=0.25 and x=0.42, and then starts to increase and reaches a maximum of ∼8.6K at x=0.81 followed by a decline to ∼6.7K when x approaches the stoichiometric value 1. In this case, the transition of the initial high entropy alloy bcc structure to the fcc structure of high entropy nitrides proceeds slowly and leads to a wide x range in which TC is suppressed. The analysis shows that the TC vs x course and the TC enhancement in high entropy nitrides depend on the valence electron concentration of the initial high entropy alloy, as higher values accelerate the tendency to form a fcc structure and are less sensitive to the localization of otherwise mobile electrons in metallic high entropy alloys due to their bonding to N atoms. However, other parameters, such as the atomic size difference of the metallic constituents and their affinity towards nitrogen, also have to be considered.

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Phys. Rev. Materials 10, 064805– Published 29 June, 2026
  • Received 16 December 2025
  • Revised 5 March 2026
  • Accepted 9 June 2026
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