Quantum description of dissipation in normal metals and short constrictions

Abstract

The dissipation in a normal metal with impurities, which serves as a shunt to a Josephson junction, is described on a quantum-mechanical level. The derivation is based on the microscopic many-body theory of this system. No further approximations are made other than those which are also used in the classical limit and which lead to Ohm’s law. We obtain an effective action which agrees with the one derived by Caldeira and Leggett from a phenomenological model. Different results are obtained for the dissipation in a short constriction between two metals.