TEMPERATURE-DEPENDENCE OF THE RATE OF DEFECT TUNNELING IN METALS

Recent measurements of the rate of single-defect tunneling in Bi wires at low temperatures (0.12.0 K) are mainly consistent with theoretical predictions based on a dissipation mechanism that couples the defect tunneling to low-energy excitations of the electrons. A deviation from this prediction is observed on the high-temperature side of the experimental range. We present a theory that accounts for this deviation based on the introduction of tunneling from another pair of levels of higher energy than the pair responsible for the lower-temperature behavior. © 1995 The American Physical Society.