Effect of impurities on the superheating field of type-Ⅱ superconductors

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摘要：

We consider the effect of nonmagnetic and magnetic impurities on the superheating field H_s in a type-Ⅱ superconductor. We solved the Eilenberger equations, which take into account the nonlinear pairbreaking of Meissner screening currents, and calculated H_S(T) for arbitrary temperatures and impurity concentrations in a single-band s -wave superconductor with a large Ginzburg-Landau parameter. At low temperatures, nonmagnetic impurities suppress a weak maximum in H_S(T), which has been predicted for the clean limit, resulting, instead, in a maximum of H_s as a function of impurity concentration in a moderately clean limit. It is shown that nonmagnetic impurities weakly affect H_s even in the dirty limit, while magnetic impurities suppress both H_s and the critical temperature T_c. The density of quasiparticles states N(∈) is strongly affected by an interplay of impurity scattering and current pairbreaking. We show that a clean superconductor at H = H_s is in a gapless state, but a quasiparticle gap ∈_g in N(∈) at H = H_s appears as the concentration of nonmagnetic impurities increases. As the nonmagnetic scattering rate α increases above α_c = 0.36, the quasiparticle gap ∈_g{α) at H = H_s increases, approaching ∈_g ≈ 0.32△_0 in the dirty limit α 》1, where △_0 is the superconducting gap parameter at zero field. The effects of impurities on H_s can be essential for the nonlinear surface resistance and superconductivity breakdown by strong RF fields.

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magnetic properties mixed states, critical fields, and surface sheaths mesoscopic and nanoscale systems

DOI：

10.1103/physrevb.85.054513

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年份：

2012