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TT: Fachverband Tiefe Temperaturen
TT 25: Correlated Electrons: Quantum-Critical Phenomena 1
TT 25.5: Vortrag
Mittwoch, 28. März 2012, 10:30–10:45, H 3010
Quantum criticality of the sub-ohmic spin-boson model — •Stefan Kirchner1,2, Kevin Ingersent3, and Qimiao Si4 — 1Max Planck Institute for the Physics of Complex Systems — 2Max Planck Institute for Chemical Physics of Solids — 3Department of Physics, University of Florida — 4Department of Physics & Astronomy, Rice University
The sub-ohmic spin-boson model has a quantum critical point separating a delocalized phase in which the impurity degree of freedom is quenched and a boson-dominated localized phase that retains a two-fold local-moment degree of freedom. Whether this quantum phase transition is described by a φ4-theory has recently received considerable attention. Here, we present an analysis of both the leading and subleading terms in the temperature dependence of the inverse static local spin susceptibility calculated using a numerical renormalization-group method. This provides evidence that the quantum critical point is interacting in cases where the quantum-to-classical mapping would predict mean-field behavior. We attribute the violation of the quantum-to-classical mapping to a Berry-phase term in a continuum path-integral representation of the model.