Lw. Chen et Mc. Marchetti, AC RESPONSE OF THE FLUX-LINE LIQUID IN THE HIGH-T(C) SUPERCONDUCTORS, Physical review. B, Condensed matter, 50(9), 1994, pp. 6382-6393
We use a hydrodynamics theory to discuss the response of a viscous flu
x-line liquid to an ac perturbation applied at the surface of the samp
le. The theory incorporates viscoelastic effects and describes the cro
ssover between liquidlike and solidlike response of the vortex array a
s the frequency of the perturbation increases. A large viscosity from
flux-line interactions and entanglement leads to viscous screening of
surface fields. As a result, two frequency-dependent length scales are
needed to describe the penetration of an ac field. For large viscosit
ies the imaginary part of the ac permeability can exhibit, in addition
to the well-known peak associated with flux diffusion across the samp
le, a low-frequency peak corresponding to the transition from solidlik
e to liquidlike behavior.