Communication: spin-boson model with diagonal and off-diagonal coupling to two independent baths: ground-state phase transition in the deep sub-Ohmic regime.
We investigate a spin-boson model with two boson baths that are coupled to two perpendicular components of the spin by employing the density matrix renormalization group method with an optimized boson basis. It is revealed that in the deep sub-Ohmic regime there exists a novel second-order phase transition between two types of doubly degenerate states, which is reduced to one of the usual types for nonzero tunneling. In addition, it is found that expectation values of the spin components display jumps at the phase boundary in the absence of bias and tunneling.
Division of Materials Science, Nanyang Technological University, Singapore 639798, Singapore.
Yang
Y
Zhao
State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
Yao
Y
Yao
Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
Vladimir
V
Chernyak
Division of Materials Science, Nanyang Technological University, Singapore 639798, Singapore.
Yang
Y
Zhao