MAGNETIZATION RELAXATION VIA QUANTUM AND CLASSICAL VORTEX MOTION IN A BOSE GLASS SUPERCONDUCTOR

I show that in a Bose glass superconductor with high jc and at low T the magnetization relaxation (S), dominated by quantum tunneling, is jc, which crosses over to the conventional classical rate T/jc at higher T and lower jc, with the crossover T*∼jc3/2. I argue that due to interactions between flux lines there exist three relaxation regimes, depending on whether B<Bφ, Bφ, B>Bφ, corresponding to strongly pinned Bose glass with large jc2, Mott insulator with vanishing S, and weakly pinned Bose glass characterized by small jc1. I discuss the effects of interactions on jc and focus attention on a recent experiment which is consistently described by the theory. © 1995 The American Physical Society.