Abstract
We propose a general extended coherent state approach to the qubit (or fermion) and multimode boson coupling systems. The application to the spin-boson model with the discretization of a bosonic bath with arbitrary continuous spectral density is described in detail, and very accurate solutions can be obtained. The quantum phase transition in the nontrivial sub-Ohmic case can be located by the fidelity and the order-parameter critical exponents for the bath exponents can be correctly given by the fidelity susceptibility, demonstrating the strength of the approach.
- Received 27 January 2010
DOI:https://doi.org/10.1103/PhysRevB.81.121105
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