Aft. Hoekstra et al., Temperature and magnetic-field dependence of quantum creep in various high-T-c superconductors, PHYS REV B, 59(10), 1999, pp. 7222-7237
To investigate the quantum tunneling of almost macroscopic vortex segments
we measured the normalized relaxation rate Q of superconducting currents fo
r various high-T-c superconductors (HTS's) down to 100 mK in magnetic field
s up to 7 T. At fields below congruent to 0.5 T, Q is essentially independe
nt of T in the temperature regime between thermally activated and quantum m
otion as theoretically expected. However, at higher fields, we find an unex
pected linear T dependence of Q persisting down to the lowest temperatures
in all investigated samples. Since these compounds were chosen to represent
the distinct classes of dirty and clean HTS's, the extrapolated Q(T = 0) v
alues are used to discuss the theoretical models for quantum creep in the c
lean and dirty limits. Based on this discussion we propose a semiempirical
interpolation formula for Q(T = 0) which is also valid for compounds in bet
ween the dirty and clean limits. [S0163-1829(99)00806-1].