No Spin-Localization Phase Transition in the Spin-Boson Model without Local Field  

作　　者：刘涛 冯芒 黎雷 杨万里 汪克林 

机构地区：[1]State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences [2]School of Science, Southwest University of Science and Technology [3]Department of Modern Physics, University of Science and Technology of China

出　　处：《Communications in Theoretical Physics》2013年第12期637-641,共5页理论物理通讯（英文版）

基　　金：Supported by National Fundamental Research Program of China under Grant No.2012CB922102;National Natural Science Foundation of China under Grant Nos.10974225 and 11004226;State Key Laboratory Funding of WIPM

摘　　要：We explore the spin-boson model in a special case, i.e., with zero local field. In contrast to previous studies, we find no possibility for quantum phase transition （QPT） happening between the localized and delocalized phases, and the behavior of the model can be fully characterized by the even or odd parity as well as the parity breaking, instead of the QPT, owned by the ground state of the system. The parity breaking mentioned in our case is completely different from the spontaneously broken symmetry relevant to the conventionally defined QPT in previous studies. Our analytical treatment about the eigensolution of the ground state of the model presents for the first time a rigorous proof of no- degeneracy for the ground state of the model, which is independent of the bath type, the degrees of freedom of the bath and the calculation precision. We argue that the QPT mentioned previously appears due to incorrect employment of the ground state of the model and/or unreasonable treatment of the infrared divergence existing in the spectral functions for Ohmic and sub-Ohmic dissipations.

关 键 词：spin-boson model localization phase transition parity breaking 

分 类 号：O572.2[理学—粒子物理与原子核物理]