title: Spontaneous symmetry breaking and bifurcations in ground-state fidelity for quantum lattice systems.
abstract: Spontaneous symmetry breaking occurs in a system when its Hamiltonian possesses a certain symmetry, whereas the ground-state wave functions do not preserve it. This provides such a scenario that a bifurcation, which breaks the symmetry, occurs when some control parameter crosses its critical value. It is unveiled that the ground-state fidelity per lattice site exhibits such a bifurcation for quantum lattice systems undergoing quantum phase transitions. The significance of this result lies in the fact that the ground-state fidelity per lattice site is universal, in the sense that it is model independent, in contrast to (model-dependent) order parameters. This fundamental quantity may be computed by exploiting the developed tensor network algorithms on infinite-size lattices. We illustrate the scheme in terms of the quantum Ising model in a transverse magnetic field and the spin-1/2 XYX model in an external magnetic field on an infinite-size lattice in one spatial dimension.
authors.affiliation: Centre for Modern Physics and Department of Physics, Chongqing University, Chongqing 400044, People's Republic of China.
authors.forename: Jian-Hui
authors.initials: JH
authors.lastname: Zhao
authors.forename: Hong-Lei
authors.initials: HL
authors.lastname: Wang
authors.forename: Bo
authors.initials: B
authors.lastname: Li
authors.forename: Huan-Qiang
authors.initials: HQ
authors.lastname: Zhou