Condensed Matter Seminar Series

Title: Spin Correlations and Free Magnetic Moments in Disordered Metals

Stefan Kettemann

University of Hamburg

Tuesday March 21,  11:30 am,  Room 298,  Physics Building

Abstract: A local magnetic impurity is known to change the whole ground state  of a Fermi liquid due to correlations created by the exchange interaction between its spin and the delocalized  electrons in a metal. As a  result,  the electron scattering and thereby the resistance is enhanced,  and the magnetic impurity spin is screened at low temperatures, the  Kondo effect. On the other hand, the exponential increase of the low temperature resistance of  disordered metals, Anderson localization, is the macroscpic manifestation of quantum coherent scattering of the electrons from impurities.
    One is thus lead to the question how in low-dimensional  disordered metals with magnetic impurities both effects, the Kondo effect and Anderson localization, compete with each other. We present recent results, showing how the Kondo effect is quenched  by Anderson localization, but  Anderson localization is  enhanced by the Kondo effect. The resulting quantum pase diagram of  disordered, correlated   low dimensional electron systems is discussed [1]. Furthermore, the Kondo temperature itself is found to be  distributed with a width that exceeds the expectations from the analogue of the Anderson Theorem [2,3]. Possible consequences at finite temperature, like non-Fermi liquid behavior and anomalous temperature dependence of the dephasing rate, are discussed and compared with experiments.

[1] S. K., Proceedings of the V. Rencontre de Moriond (2004)
[2] S. K. and M.E. Raikh, Phys. Rev. Lett. 90, 146601 (2003)
[3] S.K. And E. Mucciolo, arXiv:cond-mat/0509251, to appear in JETP  Lett. ( March 2006)