Self-heating versus quantum creep in bulk superconductors

We have performed simultaneous measurements of magnetic relaxation and the accompanying power dissipation in a number of BiSrCaCuO crystals at temperatures between 0.5 and 4.2 K. The nonvanishing relaxation rate in bulk superconductors at low temperatures, recently discussed as evidence of a quantum tunneling of vortices, is argued to be governed by self-heating of the superconductor by moving vortices.