KONDO EFFECT IN NON - EQUILIBRIUMTheory

In diiusive Cu and Au quantum wires at nite transport voltage U the non-equilibrium distribution function f(E; U) exhibits scaling behavior, f(E; U) = f(E=eU), indicating anomalous energy relaxation processes in these wires. We show that in nonequilibrium the Kondo eeect, generated either by magnetic impurities (single-channel Kondo eeect) or possibly by non-magnetic, degenerate two-level systems (two-channel Kondo eeect), produces such scaling behavior as a consequence of a Korringa-like (pseudo)spin relaxation rate / U and of damped pow-erlaw behavior of the impurity spectral density as a remnant of the Kondo strong coupling regime at low temperature but high bias. The theoretical, scaled distribution functions coincide quantitatively with the experimental results, the impurity concentration being the only adjustable parameter. This provides strong evidence for the presence of Kondo defects, either single-or two-channel, in the experimental systems. The relevance of these results for the problem of dephasing in mesoscopic wires is discussed brieey.