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TT: Fachverband Tiefe Temperaturen

TT 50: Correlated Electrons: Quantum-Critical Phenomena - Theory

TT 50.4: Vortrag

Dienstag, 1. April 2014, 14:45–15:00, BEY 81

Critical phenomena of the two-channel spin-boson model — •Benedikt Bruognolo¹, Andreas Weichselbaum¹, Jan von Delft¹, and Matthias Vojta² — ¹Physics Department, Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Ludwig-Maximilians-Universität München, 80333 München, Germany — ²Institut für Theoretische Physik, Technische Universität Dresden, 01062 Dresden, Germany

In recent years bosonic quantum impurity models have attracted significant attention in the context of quantum phase transitions. Numerical approaches to study the critical properties in such models face additional challenges arising from the bosonic nature of the bath modes, that are not present in purely fermionic systems.
Guo et al. [1] presented a powerful numerical method based on a combination of NRG and DMRG, which overcomes the problem of a diverging bosonic state space by variationally constructing an optimized boson basis on each site of the Wilson chain. We discuss a symmetry improved application of this method to the sub-ohmic spin-boson model with two symmetrically coupled bosonic baths and focus on its critical properties, which so far had been an open question. We present the first numerical study of the critical points, which in combination with RG results allows a description of the critical phenomena of this model for a wide range of parameters.
C. Guo, A. Weichselbaum, J. von Delft, M. Vojta, Phys. Rev. Lett. 108, 160401 (2012)