Quantum Fidelity and Thermal Phase Transitions in a Two-Dimensional Spin System
WANG Bo1, HUANG Hai-Lin2, SUN Zhao-Yu2**, KOU Su-Peng1
1Department of Physics, Beijing Normal University, Beijing 100875 2School of Electrical and Electronic Engineering, Wuhan Polytechnic University, Wuhan 430000
Abstract：We investigate the ability of quantum fidelity in detecting the classical phase transitions (CPTs) in a two-dimensional Heisenberg–Ising mixed spin model, which has a very rich phase diagram and is exactly soluble. For a two-site subsystem of the model, the reduced fidelity (including the operator fidelity and the fidelity susceptibility) at finite temperatures is calculated, and it is found that an extreme value presents at the critical temperature, thus shows a signal for the CPTs. In some parameter region, the signal becomes blurred. We propose to use the "normalized fidelity susceptibility" to solve this problem.
2012, Vol. 29 
