Flux motion by quantum tunneling

Abstract

At low temperatures, large, temperature-independent magnetic relaxation effects are found in the high-temperature superconducting ceramics as well as in the organic superconductors, giving evidence that, at these temperatures, vortex motion involves mainly a form of macroscopic quantum tunneling. The measured tunneling rates at low magnetic induction and in the limit T → 0, as well as the crossover temperatures T_qc from the quantum to the classical regime, are in excellent agreement with the values for single vortex tunneling calculated within the framework of the quantum collective creep theory of Blatter, Geshkenbein and Vinokur. Quantum tunneling in the heavy fermion superconductor UPt₃, on the other hand, cannot be explained with the aforementioned theory.