Nonlinear electrodynamic model for anisotropic type-II superconductors

This article introduces a theoretical model for analyzing nonlinear electrodynamic effects induced by flux-motion in anisotropic type-II superconductors. The model is phenomenological and is based on the continuum analysis of flux-dynamics of type-II superconductors in the mixed state, which accounts for both the critical-state effect and material anisotropic effect. Besides, a complete set of nonlinear field equations and effective constitutive equations are formulated in combination with generalized London equations and Maxwell's equations, where the incomplete Meissner effect and the normal conduction fluid effect are also taken into account. In contrast to the well-known Bean's critical-state model, the new model may account for the effect of localized vibration of flux-lines in ac fields and the possible effect of inertia of flux-lines in the superconductor, which may be of particular interest in studying microwave applications of some type-II superconductors at extremely high- frequencies. By analyzing quantitatively the vortex dynamic effects, we propose some modifications of Bean's critical-state model in treating electrodynamic problems of type-II superconductors in ac fields of extremely high frequencies.