We construct a model Hamiltonian for
S=2 spin chain, where a variable parameter $\ensuremath{\alpha}$ is introduced. The edge spin is
S=1 for $\ensuremath{\alpha}=0$ and
S=3/2 for $\ensuremath{\alpha}=1$. Due to the topological distinction of the edge states, these two phases must be separated by one or several topological quantum phase transitions. We have studied the quantum phase transition by density matrix renormalization group calculation and proposed a phase diagram for this model.
One-dimensional gapped spin chains with symmetry
PSU(N)=SU(N)/ZN are known to possess
N different topological phases. In this paper, we introduce a nonlocal string order parameter which characterizes each of these
N phases unambiguously. Numerics confirm that our order parameter allows one to extract a quantized topological invariant from a given nondegenerate gapped ground state wave function. Discontinuous jumps in the discrete topological order that arise when varying physical couplings in the Hamiltonian may be used to detect quantum phase transitions between different topological phases.
We present a new model of quantum phase transitions in matrix product systems of one-dimensional spin-1 chains and study the phases coexistence phenomenon. We find that in the thermodynamic limit the proposed system has three different quantum phases and by adjusting the control parameters we are able to realize any phase, any two phases equal coexistence and the three phases equal coexistence. At every critical point the physical quantities including the entanglement are not discontinuous and the matrix product system has long-range correlation and N -spin maximal entanglement. We believe that our work is helpful for having a comprehensive understanding of quantum phase transitions in matrix product states of one-dimensional spin chains and of certain directive significance to the preparation and control of one-dimensional spin lattice models with stable coherence and N -spin maximal entanglement.