Quantum phase transition in the sub-Ohmic spin-boson model: quantum Monte Carlo study with a continuous imaginary time cluster algorithm.
A continuous time cluster algorithm for two-level systems coupled to a dissipative bosonic bath is presented and applied to the sub-Ohmic spin-boson model. When the power s of the spectral function Jomega proportional, variant omegas is smaller than 1/2, the critical exponents are found to be classical, mean-field like. Potential sources for the discrepancy with recent renormalization group predictions are traced back to the effect of a dangerously irrelevant variable.
Winter
André
A
Theoretische Physik, Universität des Saarlandes, 66041 Saarbrücken, Germany.
Rieger
Heiko
H
Vojta
Matthias
M
Bulla
Ralf
R