27 research outputs found
Edge Modes in the Intermediate-D and Large-D Phases of the S=2 Quantum Spin Chain with XXZ and On-Site Anisotropies
We investigate the edge modes at T=0 in the intermediate-D (ID) phase and the
large-D (LD) phase of the S=2 quantum spin chain with the XXZ anisotropy and
the generalized on-site anisotropies by use of the DMRG. There exists a gapless
edge mode in the ID phase, while no gapless edge mode in the LD phase. These
results are consistent with the physical pictures of these phases. We also show
the ground-state phase diagrams obtained by use of the exact diagonalization
and the level spectroscopy analysis.Comment: Submitted to "Proceedings of the International Conference on Strongly
Correlated Electron Systems (SCES2013)
Haldane to Dimer Phase Transition in the Spin-1 Haldane System with Bond-Alternating Nearest-Neighbor and Uniform Next-Nearest-Neighbor Exchange Interactions
The Haldane to dimer phase transition is studied in the spin-1 Haldane system with bond-alternating nearest-neighbor and uniform next-nearest-neighbor exchange interactions, where both interactions are antiferromagnetic and thus compete with each other. By using a method of exact diagonalization, the ground-state phase diagram on the ratio of the next-nearest-neighbor interaction constant to the nearest-neighbor one versus the bond-alternation parameter of the nearest-neighbor interactions is determined. It is found that the competition between the interactions stabilizes the dimer phase against the Haldane phase
Ground-State Phase Diagram of an Anisotropic S=1 Ferromagnetic-Antiferromagnetic Bond-Alternating Chain
By using mainly numerical methods, we investigate the ground-state phase
diagram (GSPD) of an ferromagnetic-antiferromagnetic bond-alternating
chain with the and the on-site anisotropies. This system can be mapped
onto an anisotropic spin-2 chain when the ferromagnetic interaction is much
stronger than the antiferromagnetic interaction. Since there are many quantum
parameters in this system, we numerically obtained the GSPD on the plane of the
magnitude of the antiferromagnetic coupling versus its anisotropy, by use
of the exact diagonalization, the level spectroscopy as well as the
phenomenological renormalization group. The obtained GSPD consists of six
phases. They are the 1, the large- (LD), the intermediate- (ID), the
Haldane (H), the spin-1 singlet dimer (SD), and the N\'eel phases. Among them,
the LD, the H, and the SD phases are the trivial phases, while the ID phase is
the symmetry-protected topological phase. The former three are smoothly
connected without any quantum phase transitions. It is also emphasized that the
ID phase appears in a wider region compared with the case of the GSPD of the
anisotropic spin-2 chain with the and the on-site anisotropies. We also
compare the obtained GSPD with the result of the perturbation theory.Comment: to be published in JPS Conf. Se
How to distinguish the Haldane/Large-D state and the intermediate-D state in an S=2 quantum spin chain with the XXZ and on-site anisotropies
We numerically investigate the ground-state phase diagram of an S=2 quantum
spin chain with the and on-site anisotropies described by , where denotes the XXZ anisotropy parameter of the
nearest-neighbor interactions and the on-site anisotropy parameter. We
restrict ourselves to the and case for simplicity. Our main
purpose is to obtain the definite conclusion whether there exists or not the
intermediate- (ID) phase, which was proposed by Oshikawa in 1992 and has
been believed to be absent since the DMRG studies in the latter half of 1990's.
In the phase diagram with and there appear the XY state, the
Haldane state, the ID state, the large- (LD) state and the N\'eel state. In
the analysis of the numerical data it is important to distinguish three gapped
states; the Haldane state, the ID state and the LD state. We give a physical
and intuitive explanation for our level spectroscopy method how to distinguish
these three phases.Comment: Proceedings of "International Conference on Frustration in Condensed
Matter (ICFCM)" (Jan. 11-14, 2011, Sendai, Japan
Ground state of an distorted diamond chain - model of
We study the ground state of the model Hamiltonian of the trimerized
quantum Heisenberg chain in which
the non-magnetic ground state is observed recently. This model consists of
stacked trimers and has three kinds of coupling constants between spins; the
intra-trimer coupling constant and the inter-trimer coupling constants
and . All of these constants are assumed to be antiferromagnetic. By
use of the analytical method and physical considerations, we show that there
are three phases on the plane (, ), the dimer phase, the spin fluid phase
and the ferrimagnetic phase. The dimer phase is caused by the frustration
effect. In the dimer phase, there exists the excitation gap between the
two-fold degenerate ground state and the first excited state, which explains
the non-magnetic ground state observed in . We also obtain the phase diagram on the
plane from the numerical diagonalization data for finite systems by use of the
Lanczos algorithm.Comment: LaTeX2e, 15 pages, 21 eps figures, typos corrected, slightly detailed
explanation adde
Magnetic properties of the distorted diamond chain at T=0
We explore, at T=0, the magnetic properties of the antiferromagnetic
distorted diamond chain described by the Hamiltonian {\cal H}
= \sum_{j=1}^{N/3}{J_1 ({\bi S}_{3j-1} \cdot {\bi S}_{3j}
+ {\bi S}_{3j} \cdot {\bi S}_{3j+1})
+ J_2 {\bi S}_{3j+1} \cdot {\bi S}_{3j+2}
+ J_3 ({\bi S}_{3j-2} \cdot {\bi S}_{3j}
+ {\bi S}_{3j} \cdot {\bi S}_{3j+2})}
\allowbreak - H \sum_{l=1}^{N} S_l^z with , which well
models with , and azurite . We employ the physical
consideration, the degenerate perturbation theory, the level spectroscopy
analysis of the numerical diagonalization data obtained by the Lanczos method
and also the density matrix renormalization group (DMRG) method. We investigate
the mechanisms of the magnetization plateaux at and , and
also show the precise phase diagrams on the plane
concerning with these magnetization plateaux, where
and is the saturation magnetization. We also calculate the magnetization
curves and the magnetization phase diagrams by means of the DMRG method.Comment: 21 pages, 29 figure