Dissipative phase transition in a pair of coupled noisy two-level systems

Article

关键词: QUANTUM BROWNIAN-MOTION;    FINITE TEMPERATURES;    FLUCTUATIONS;    DYNAMICS;   

DOI  :  10.1103/PhysRevB.88.125139

来源: SCIE

【 摘 要 】

We study the renormalization group (RG) equations of a pair of spin-boson systems coupled in the z direction with each other. Each spin is coupled to a different bath of harmonic oscillators. We introduce a systematic adiabatic RG, which generalizes the first-order adiabatic renormalization previously used for the single spin-boson model, and we obtain the flow equations for the tunneling constant, the dissipation strength, and the interspin coupling up to third order in the tunneling. If one of the two spins is treated as a constant magnetization, the other spin is described by a biased spin-boson Hamiltonian. In this case the RG equations we find coincide with the ones obtained via a mapping to a long-range Ising chain. If the whole Ohmic two-spin system is considered the Kosterlitz-Thouless phase transition is replaced by a second-order phase transition. In the case of a sub-Ohmic bath our approach predicts that the two-spin system is always localized.

【 授权许可】

Free