Viscous flux motion in anisotropic type-II superconductors in low fields.

摘要

The Bardeen-Stephen model of viscous flux motion in isotropic Type-II superconductors is extended to the anisotropic case characterized by a phenomenological effective mass tensor m(sub ij). When the magnetic field is low and the vortex lines are aligned along one of the three principal axes, simple expressions for the viscosity tensor (eta)(sub ij) of the viscous flux motion are obtained as functions of m(sub ij) and the normal state conductivity tensor (sigma)(sub ij) for temperature T close to the critical temperature (Tc). For the high-temperature oxide superconductors the theory predicts that (eta)(sub b)(sup (a)):(eta)(sub b)(sup (c)):(eta)(sub c)(sup (a)) (approx) 1:4(gamma):3(gamma)(sup 2), where (eta)(sub i)(sup (j)) is the viscosity for the motion along the i-axis of a vortex parallel to the j-axis and (gamma) = (radical)m(sub c)/m(sub a) is the anisotropy parameter (m(sub i), i = a,b,c, are the principal values of the mass tensor satisfying m(sub a) (approx) m(sub b) (much lt) m(sub c)). 9 refs., 1 fig.