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The ground-state properties of the spin-(1/2, 1) mixed-spin XXZ chain with single-ion anisotropy (D) are investigated by the infinite time-evolving block decimation (iTEBD) method. A ground-state phase diagram including three phases, i.e., a fully polarized phase, an XY phase and a ferrimagnetic phase, is obtained. The ferrimagnetic phase is found to extend to the regions with (Δ > 1, D > 0) and (Δ < 1, D < 0), where Δ denotes the coupling anisotropy between the localized spins. By the discontinuous behavior of bipartite entanglement, quantum phase transitions (QPTs) between the XY phase and the other two phases are verified to be of the first-order. Furthermore, two constant spontaneous magnetization values (Mz = 3/2 and 1/2) are observed in the fully polarized and the ferrimagnetic phases, respectively. In both cases of Δ → +∞ and D → -∞, the ground state tends to the Ising limit. In addition, both the long-range ferromagnetic and antiferromagnetic orders are found to coexist in the whole ferrimagnetic phase. [ABSTRACT FROM AUTHOR]

By the infinite time-evolving block decimation (iTEBD) algorithm, the magnetization process of the spin- 3 2 bond-alternating Ising chain with single-ion anisotropy ( D ) is investigated. Magnetization plateaus including detailed magnetization structures of three different cases are uncovered, and three rich ground-state phase diagrams are explicitly determined. Especially, for the uniform antiferromagnetic case, a phase transition line at D = J , which divides the M z =0 ( M z = 1 2 ) plateau into two phases, are detected by the magnetization structure and the ground-state energy, and a updated phase diagram is proposed. Such a transition line was not recognized by the average magnetization previously. A same transition line ( D = J ) is also detected in the phase diagram of the antiferromagnetic-ferromagnetic alternating case. Magnetization plateaus are found to be easily induced for the classical Ising systems without quantum fluctuations, and the single-ion anisotropy plays a key role in the formation of M z = 1 2 and 1 plateaus in the present model. [ABSTRACT FROM AUTHOR]

The ground-state properties of the spin-1/2 Ferromagnetic–Ferromagnetic–Antiferromagnetic (F–F–AF) trimerized chain are investigated by the infinite time-evolving block decimation (iTEBD) method. A ground-state phase diagram including three different phases, i.e. , a fully polarized phase, a 1/3 plateau phase, and a non-plateau phase, is obtained. All the quantum phase transitions (QPTs) can be described well by the model independent bipartite entanglement. QPTs between the non-plateau phase and the other two phases belong to the second-order category. Doubly degenerate entanglement spectrum and nontrivial string order are observed in the 1/3 plateau phase, which can be used to distinguish it from the other phases. By the scaling behavior of the bipartite entanglement, the central charge of the critical non-plateau phase is determined to be c ≃ 1. [ABSTRACT FROM AUTHOR]

Abstract: By the infinite time-evolving block decimation (iTEBD) technique, the magnetization process and the quantum phase transitions (QPTs) in the spin-1 XXZ model with single-ion anisotropy under external field are investigated. It is found that, all the phases will be destroyed by a sufficient strong magnetic field. Before they come into the ferromagnetic (fully polarized) phase, some interesting intermediate phases are induced. A pseudo order with finite truncation dimension χ can be used to describe the XY1 phase. Especially, the O xy i with finite χ is found to be nonzero in the XY1 phase, but vanishes in the XY2 phase. It means that two kinds of XY phases can be distinguished by the pseudo order parameter O xy i . All the QPTs can be described by the behavior of the entanglement entropy and the ground-state energy. QPTs from the XY phase to the large-D, Haldane, and antiferromagnetic phases are found to be infinite-order BKT type transitions, but the QPTs from the XY1 phase to the ferromagnetic phase and XY2 have second-order characters. In addition, doubly degenerate entanglement spectra are observed in the Haldane phase. [Copyright &y& Elsevier]

Abstract: By the simple updated infinite time-evolving block decimation (iTEBD) algorithm, the magnetization process and phase diagram of the antiferromagnetic and ferromagnetic spin-1 Ising model with single-ion anisotropy on the Z=3 Bethe lattice have been investigated. For the antiferromagnetic case, three magnetization plateaus, i.e., M z =0, 1/2, and 1, are observed. The novel 1/2 plateau state, which was reported on the 1D spin chain previously, is shown to exist on the Z=3 Bethe lattice. For this classical model without any quantum fluctuations, the 1/2 magnetization plateau is suggested to be caused by the stability of spatially modulated spin structures. Furthermore, in the plateau, two different phases (an ideal Néel phase and an ideal large-D phase) are distinguished. The phase boundaries are determined exactly, and a rich phase diagram including four phases is obtained. In addition, the magnetization process of the ferromagnetic case is also discussed, but a relatively simple phase diagram without 1/2 plateau phase is determined. According to the energy level crossing, all the phase transitions in both cases are verified to be first-order ones. [Copyright &y& Elsevier]

Abstract: By the infinite time-evolving block decimation (iTEBD) technique, the magnetization process in spin-1 Ising model with single-ion anisotropy under external field is investigated in the thermodynamic limit. An updated phase diagram is proposed, and the detailed magnetic structures of the phase diagram are uncovered. It must be noted that two interesting phases with same magnetization plateau (M z =0) but different magnetic structures are distinguished. Furthermore, they are verified to be an ideal Néel phase and an ideal large-D phase respectively. In addition, a first-order quantum phase transition line between them is determined to be at D=1. [Copyright &y& Elsevier]