We have measured the complex surface impedance of 2H-NbSe_2 in the mixed state over a wide range of magnetic field(0-2T) and frequency(10-3000MHz). A crossover between pinned and viscous dynamics of flux-lines is observed at a pinning frequency, ωp. The measured ωp is compared to that predicted by a single-particle "washboard potential" model for the pinning interaction. When the flux lattice is prepared in an ordered state by zero-field cooling or by driving it with a large current, ωp is in good agreement with the predicted value. However, when it is prepared in a metastable disordered state by field cooling, ωp is nearly two orders of magnitude higher than expected indicating a complete break-down of the single-particle model.
@article{arxiv.cond-mat/9703053,
title = {AC Dynamics and Metastability of a Flux-Line Lattice},
author = {W. Henderson and E. Y. Andrei and M. J. Higgins and S. Bhattacharya},
journal= {arXiv preprint arXiv:cond-mat/9703053},
year = {2015}
}