Parts | Days | Selection | Search | Downloads | Help

TT: Tiefe Temperaturen

TT 34: Correlated Electrons - Quantum Impurities, Kondo Physics

TT 34.4: Talk

Wednesday, March 9, 2005, 10:30–10:45, TU H104

Structure of Quantum Critical Points in Impurity Models — •Hyun-Jung Lee¹, Ralf Bulla¹, and Ning-Hua Tong² — ¹Theoretische Physik III, Universität Augsburg — ²Institut für Theorie der Kondensierten Materie, Universität Karlsruhe

The numerical renormalization group method is used to investigate zero temperature phase transitions in single-impurity models, where an impurity couples to a non-trivial fermionic bath (Pseudogap Anderson model) or to a (sub)ohmic bosonic bath (Spin-Boson Model). In both cases, zero temperature phase transitions occur between two different phases whose fixed points can be built up of non-interacting single-particle states. These trivial phases are separated by lines of quantum critical points. The structure of these quantum critical points can be understood close to certain values of the bath exponents which turn out to play the role of upper and lower critical dimensions. A complete description of the quantum critical many-particle spectra is achieved using suitable marginal operators.