Ab initio calculations of Hc2 in type-II superconductors: Basic formalism and model calculations

Article

关键词: UPPER CRITICAL-FIELD;    FERMI-SURFACE HARMONICS;    TEMPERATURE-DEPENDENCE;    MAGNETIC-PROPERTIES;    PURITY DEPENDENCE;    WAVE SUPERCONDUCTORS;    ANGULAR-DEPENDENCE;    NUCLEATION FIELDS;    ANISOTROPY;    OSCILLATIONS;   

DOI  :  10.1103/PhysRevB.70.224522

来源: SCIE

【 摘 要 】

Detailed Fermi-surface structures are essential to describe the upper critical field H-c2 in type-II superconductors, as first noticed by and Hohenberg and Werthamer [Phys. Rev. 153, 493 (1967)] and shown explicitly by Butler for high-purity cubic Niobium [Phys. Rev. Lett. 44, 1516 (1980)]. We derive an H-c2 equation for classic type-II superconductors that is applicable to systems with anisotropic Fermi surfaces and/or energy gaps under arbitrary field directions. It can be solved efficiently by using Fermi surfaces from ab initio electronic-structure calculations. Thus, it is expected to enhance our quantitative understanding on H-c2. Based on the formalism, we calculate H-c2 curves for Fermi surfaces of a three-dimensional tight-binding model with cubic symmetry, an isotropic gap, and no impurity scatterings. It is found that, as the Fermi surface approaches to the Brillouin zone boundary, the reduced critical field h*(T/T-c), which is normalized by the initial slope at T-c, is enhanced significantly over the curve for the spherical Fermi surface with a marked upward curvature. Thus, the Fermi-surface anisotropy can be a main source of the upward curvature in H-c2 near T-c.

【 授权许可】

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