Dresden 2009 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 6: Postersession Correlated Electrons: (General) Theory, Low-Dimensional Systems, Kondo Physics, Heavy Fermions, Quantum-Critical Phenomena
TT 6.60: Poster
Montag, 23. März 2009, 13:00–16:45, P1A
Quantum phase transition of the sub-Ohmic spin-boson model — •André Winter and Heiko Rieger — Theoretische Physik, Universität des Saarlandes, PF 151150, D-66041 Saarbrücken
Quantum dissipation plays a highly interesting role in several fields of physics, like the decoherence of qubits or charge transfer in donor-acceptor systems. Therefore, we study these quantum-dissipative effects via the spin-boson model, which describes a two-level system coupled to a bosonic bath with a spectral density J(ω) ∝ ωσ . We use an advanced Monte Carlo cluster algorithm to explore the quantum phase transition between localized and delocalized phase of this model in the sub-Ohmic regime ( 0 < σ < 1). The applied method, which based on the path integral approach to Quantum Monte-Carlo computations, works without discretization and uses cluster updates of continuous worldline-segments to investigate the quantum critical point effectively. We compute the critical exponents of the phase transition and their dependence on the bath exponent characterizing the low frequency behaviour of the spectral function of the bosonic bath.