Quantum phase transitions in spin-1 compass chains

The ground-state phase diagram and quantum phase transitions (QPTs) in a spin-1 compass chain are investigated by the infinite time-evolving block decimation (iTEBD) method. Various phases are discerned by energy densities, spin correlations and entanglement entropy. A generalized string correlator is found to be capable of describing the nonlocal string order in the disordered phase. Furthermore, in the noncritical disordered phase, the spin-spin correlations are found to decay exponentially. Except for a multicritical point (J(1) = 0, J(2) = 0), the QPTs are determined to have second-order characters. In addition, the central charges on these critical phase boundaries are determined to be c = 1/2, therefore these QPTs belong to the Ising universality class.