Transport characteristics of tunnel heterostructures: Transition from the quantum to the classical limit

Abstract

Two possible mechanisms for the partial or complete loss of information contained in the quantum-mechanical phase of an electron moving in a stochastic solid-state structure are examined. The first involves phase randomization of the electron characteristics (for example, by elastic scattering of electrons on defects in thin metallic layers) and the second arises from inelastic interactions of current carriers with external degrees of freedom. With a double-barrier heterostructure as an example, it is shown that in the first case the quantum-mechanical approach reduces to a semiclassical method, in which the probabilities of individual events appear, rather than the quantum-mechanical probability amplitudes. The second case corresponds to a transition to the classical theory of charge transport. The effect of decoherence on the differential conductivity and shot noise in double-barrier tunnelling systems with a superconducting electrode is evaluated and the changes in these owing to the transition from quantum to incoherent classical electron transport are analyzed.