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TT: Fachverband Tiefe Temperaturen

TT 25: Correlated Electrons: Quantum-Critical Phenomena 1

TT 25.3: Talk

Wednesday, March 28, 2012, 10:00–10:15, H 3010

Quantum dynamical crossover from coherent to incoherent dynamics in a Sub-Ohmic independent Boson model — •Peter Nalbach and Michael Thorwart — I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstraße 9, 20355 Hamburg, Germany

The sub-Ohmic spin-boson model shows with increasing coupling to a Sub-Ohmic bath a crossover from coherent to incoherent dynamics at zero (and at low) temperatures. The same system shows a quantum phase transition. However, in general both effects happen for different coupling strength. In order to study the connection between the dynamic crossover and the quantum phase transition we investigate an asymmetric Sub-Ohmic spin boson model and focus on the limit of vanishing tunneling. This results in a Sub-Ohmic independent Boson model which is exactly solvable. For this, we calculate the time evolution of the correlation function of the tunneling operators at zero temperature which allows to study the coherence properties even in absence of a direct tunnel coupling. Thus, we can determine the crossover coupling strength analytically. Most importantly, we compare it with numerical findings in the symmetric Sub-Ohmic spin boson model.