Wickramaratne Darshana, Mazin I I
Center for Computational Materials Science, U.S. Naval Research Laboratory, Washington, DC, 20375, USA.
Department of Physics and Astronomy, George Mason University, Fairfax, VA, 22030, USA.
Nat Commun. 2022 May 2;13(1):2376. doi: 10.1038/s41467-022-29213-8.
When sulfur and silicon are incorporated in monolayer 2H-NbSe the superconducting transition temperature, T, has been found to vary non-monotonically. This was assumed to be a manifestation of fractal superconductivity. Using first-principles calculations, we show that the nonmonotonic dependence of T is insufficient evidence for multifractality. A unifying aspect in our study are selenium vacancies in NbSe, which are magnetic pair-breaking defects that we propose can be present in considerable concentrations in as-grown NbSe. We show that sulfur and silicon can occupy the selenium sites and reduce the pair-breaking effect. Furthermore, when sulfur is incorporated in NbSe, the density of states at the Fermi level and the proximity to magnetism in the alloy are both reduced compared to the parent compound. Based on our results, we propose an alternative explanation of the non-monotonic change in T which does not require the conjecture of multifractality.
当硫和硅掺入单层2H-NbSe₂时，已发现超导转变温度T呈非单调变化。这被认为是分形超导的一种表现。通过第一性原理计算，我们表明T的非单调依赖性不足以作为多重分形的证据。我们研究中的一个统一因素是NbSe₂中的硒空位，它们是磁对破坏缺陷，我们提出在生长的NbSe₂中可能存在相当高浓度的此类缺陷。我们表明硫和硅可以占据硒位点并降低对破坏效应。此外，当硫掺入NbSe₂时，与母体化合物相比，费米能级处的态密度以及合金中与磁性的接近程度都降低了。基于我们的结果，我们提出了对T非单调变化的另一种解释，该解释不需要多重分形的推测。
