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TT: Tiefe Temperaturen
TT 16: Korrelierte Elektronen: Quantenstörstellen, Kondo-Physik
TT 16.1: Talk
Tuesday, March 9, 2004, 16:45–17:00, H19
Flowing uphill: From single- to multi-channel Kondo effect in quantum dots due to weak charging energies in the leads — •Serge Florens1 and Achim Rosch2 — 1Institut für Theorie der Kondensierten Materie,Universität Karlsruhe, Postfach 6980, 76128 Karlsruhe — 2Institut für Theoretische Physik, Zülpicher Str.77, D-50937 Köln
We have studied a model for quantum dots which takes into account Coulomb blockade in the electrodes, a setup proposed recently by Oreg and Goldhaber-Gordon as a way to observe exotic transport in nanostructures. Even if the charging energy in the leads Ec is much smaller than the Kondo temperature TK, we find surprisingly that the long-ranged interactions destabilize the single-channel Kondo effect and induce a flow towards a multi-channel Kondo fixed point associated with a rise of the impurity entropy with decreasing temperature. Such an “uphill flow” implies a negative impurity specific heat, in contrast to all systems with local interactions. An exact solution found for a large number of channels allows us to capture this physics and to predict transport properties through the device.