title: Long-range string orders and topological quantum phase transitions in the one-dimensional quantum compass model.
abstract: In order to investigate the quantum phase transition in the one-dimensional quantum compass model, we numerically calculate non-local string correlations, entanglement entropy and fidelity per lattice site by using the infinite matrix product state representation with the infinite time evolving block decimation method. In the whole range of the interaction parameters, we find that four distinct string orders characterize the four different Haldane phases and the topological quantum phase transition occurs between the Haldane phases. The critical exponents of the string order parameters β = 1/8 and the cental charges c = 1/2 at the critical points show that the topological phase transitions between the phases belong to an Ising type of universality classes. In addition to the string order parameters, the singularities of the second derivative of the ground state energies per site, the continuous and singular behaviors of the Von Neumann entropy and the pinch points of the fidelity per lattice site manifest that the phase transitions between the phases are of the second-order, in contrast to the first-order transition suggested in previous studies.
authors.affiliation: Postdoctoral Research Station of Material Science and Engineering, Chongqing University, Chongqing 400044,The People's Republic of China. Centre for Modern Physics and Department of Physics, Chongqing University, Chongqing 400044, The People's Republic of China.
authors.forename: Hai Tao
authors.initials: HT
authors.lastname: Wang
authors.forename: Sam Young
authors.initials: SY
authors.lastname: Cho