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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.