Dresden 2011 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 23: CE: Quantum-Critical Phenomena 2

TT 23.9: Talk

Tuesday, March 15, 2011, 12:45–13:00, HSZ 105

Quantum phase transition in the paired spin-boson model — •André Winter and Heiko Rieger — Theoretische Physik, Universität des Saarlandes, Campus, 66123 Saarbrücken

We study the quantum phase transitions occurring in a system of two two-level degrees of freedom (e.g. spin-1/2) each coupled to a bath of oscillators, denoted as the paired spin-boson model. Even in the absence of a direct interaction between the two spin-1/2s the dissipative bath establishes an effective interaction causing both mutual coherence effects and disspation. We perform large scale quantum Monte Carlo simulations based on a cluster algorithm in continuous imaginary time, which we applied already successfully to the single spin-boson model [1], to determine the phase diagram in the Ohmic and sub-Ohmic regime and use finite temperature scaling to determine the critical exponents. The extension to multiple spin-1/2 degrees of freedom and an infinite spin-1/2-chain coupled to a single dissipative bosonic bath are discussed.
A. Winter, H. Rieger, M. Vojta, and R. Bulla, Phys. Rev. Lett. 102, 030601 (2009)