Impurity Effects on Superconducting Critical Temperature for Nano-structured Superconductor

Superconductors have their own superconducting critical temperature Tc. However, for nano-structured superconductors, their sizes and shapes change Tc, [1]. Nishizaki showed that high pressure torsion (HPT) make many fine grain in bulk of Nb, and make Tc higher experimentally [2]. However he also found that HPT makes Tc lower for bulk of V, and discussesed that impurities in the bulk of V affects the Tc [3].
We study the effects of size, shape, and impurity for the Tc and the mechanism of these effects, for nano-structured superconductors, using finite element method (FEM) [4]. In previous study we showed that the smaller and narrower superconductors show higher Tc [5]. In this presentation, we will talk about the impurity effects on Tc, by solving Gor’kov equations and Bogoliubov-de Gennes’s equations with the FEM.

Reference
[1] H. Suematsu, M. Kato and T. Ishida, J. Phys.: Conf. Ser. 150 (2009) 052250. [2] T. Nishizakiet al., Physica C 493 (2013) 132. [3] T. Nishizaki, The 21st Vortex matter Physics Workshop in Japan 14A2-4 [4] M. Kato, T. Ishida, T. Koyama, M. Machida, Superconductors-Materials, Properties and Applications. InTech. (2012)319. [5] M. Umeda, M. Kato, O.Sato, IEEE Trans. Appl. Supercond. 26 (2016) 8600104.