Quantum diffusion in solids

Abstract

Many characteristics of diffusion, like the Arrhenius behaviour with temperature, can occur in both classical and quantum mechanisms. The clearest examples of quantum diffusion are thus most apparent in rather special systems, notably light interstitial motion in metals. Such behaviour (especially for H isotopes bound to impurities so as to avoid precipitation, or for muons) shows isotope effects and, because the quantum aspects enter into the dynamics as well as statistics, introduces new mechanisms which compete with the standard classical diffusion channel. This paper surveys some of the key ideas, the way these are reflected in experiment, and the systems for which such behaviour is to be expected, including silicon donors and acceptors passivated by hydrogen.