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arXiv · 2607.18994

Annealing-enhanced spin-orbit effects in non-centrosymmetric superconducting NbRe films

Zahra Makhdoumi Kakhaki·Yuriy Yerin·Francesco Avitabile·Abhishek Kumar·Francesco Colangelo·Carla Cirillo·Oleksandr V. Dobrovolskiy·Carmine Attanasio
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Abstract

$\text{Nb}_{0.18}\text{Re}_{0.82}$ (NbRe) is a non-centrosymmetric superconductor with a transition temperature $T_\mathrm{c}$ reaching $9\text{ K}$ in bulk form. While bulk and single-crystalline NbRe exhibit signatures of multigap superconductivity, thin films generally display a single-gap superconducting state due to structural disorder and reduced crystallite dimensions. Here, we investigate the impact of thermal annealing on the superconducting and normal-state magnetotransport properties of NbRe films. The temperature dependence of the upper critical field, $B_{\mathrm{c2}}(T)$, is analyzed within the microscopic Werthamer--Helfand--Hohenberg (WHH) framework, while the normal-state magnetoconductivity is described using the three-dimensional Kawabata weak-localization/weak-anti-localization model. Annealing drives a pronounced change in the electronic response, manifested by a strong weak anti-localization behavior in the normal state and an upper critical field that surpasses both the conventional orbital-limiting field and the Pauli paramagnetic limit. The microscopic analysis reveals a strong intrinsic increase in the relative spin--orbit scattering strength, with the annealed film showing a significantly enhanced spin--orbit-to-dephasing field ratio. These findings provide direct, independent evidence that thermal modification of the NbRe microstructure successfully amplifies spin--orbit-mediated quantum transport, which acts as the key mechanism protecting the non-centrosymmetric superconducting state against paramagnetic pair-breaking well beyond conventional theoretical boundaries.

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Zahra Makhdoumi Kakhaki, Yuriy Yerin, Francesco Avitabile, Abhishek Kumar, Francesco Colangelo, Carla Cirillo, Oleksandr V. Dobrovolskiy, Carmine Attanasio. 2026-07-21. Annealing-enhanced spin-orbit effects in non-centrosymmetric superconducting NbRe films. https://arxiv.org/abs/2607.18994

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