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TT: Tiefe Temperaturen

TT 10: FV-internes Symposium ”Quantum Phase Transitions”

TT 10.5: Fachvortrag

Dienstag, 9. März 2004, 12:25–12:55, H18

Numerical Renormalization Group for Bosons and Fermions: Impurity Quantum Phase Transitions — •Ralf Bulla — Theoretische Physik III, Universität Augsburg

Wilson’s numerical renormalization group (NRG) has been very successful in describing magnetic impurities in a fermionic bath. Here we review some recent results on quantum phase transitions of impurity models in a general environment, including examples of local criticality. In this context, we present the generalization of the NRG to models where the impurity couples to a bosonic bath. Application of the bosonic NRG to the subohmic spin-boson model reveals a line of quantum critical points terminating in the Kosterlitz-Thouless transition for the ohmic case. Further extensions of this approach (such as the investigation of the Bose-Fermi Kondo model within the extended DMFT) are discussed.