Quantum interference and multilevel aspects of paraelectric defect relaxation processes

Abstract

The transition rates governing the relaxation behavior of paraelectric defect systems are usually treated as if they could be compounded from knowledge of the rates for simple reorientations of the defects from one directed state to another. For transitions between tunneling states, however, quantum interference, in general, plays a role. In addition to quantum interference, the generally multilevel structure of paraelectric defect energy levels causes observable rates to be related in a complicated way to the rates connecting pairs of levels separately. Both these problems are investigated for the example of a $〈111〉$ defect system in a [100] electric bias field. It is found that quantum interference and multilevel effects are most marked for low-bias fields (for which bias splitting is less than or of the order of zero-bias tunneling splittings) and low temperatures where one-phonon relaxation processes dominate. Both this low-temperature case and the high-temperature Arrhenius-like limiting rate case are investigated.