Excited state properties of the one-dimensional quantum spin systems

Magnetic properties of a one-dimensional multicomponent quantum-spin system with an excitation gap are studied based on the integrable spin model introduced by Bariev et al. [Z. Phys. B 96, 395 (1995)]. By exactly computing the magnetization, we show how a characteristic structure with plateaus and cusps appears in the magnetization process. To study the low-energy dynamics of the system, we apply a finite-size scaling analysis to the excitation spectrum, and thereby evaluate the power-law exponent as well as the enhancement factor for the low-temperature NMR relaxation rate ${1/T}_{1}.$ We discuss the critical properties of ${1/T}_{1}$ around plateaus and cusps in the magnetization curve.Magnetic properties of a one-dimensional multicomponent quantum-spin system with an excitation gap are studied based on the integrable spin model introduced by Bariev et al. [Z. Phys. B 96, 395 (1995)]. By exactly computing the magnetization, we show how a characteristic structure with plateaus and cusps appears in the magnetization process. To study the low-energy dynamics of the system, we apply a finite-size scaling analysis to the excitation spectrum, and thereby evaluate the power-law exponent as well as the enhancement factor for the low-temperature NMR relaxation rate ${1/T}_{1}.$ We discuss the critical properties of ${1/T}_{1}$ around plateaus and cusps in the magnetization curve.

arXiv:cond-mat/0101423Physical review. B, Condensed matterMar 19, 20014 citations

Magnetic double structure for S=1 and S=1/2 mixed-spin systems

義博宅島, Akihisa Koga, Norio Kawakami

We investigate the zero-temperature and the finite-temperature properties of the two-dimensional antiferromagnetic quantum spin system composed of the $s=1/2$ and $s=1$ spins. The spin excitation spectrum as well as the thermodynamic quantities are computed by means of the Schwinger-boson mean-field theory. We discuss how the magnetic double structure with the gapful and the gapless excitations is generated, and apply the results systematically to the Haldane gap system in a staggered magnetic field and also to the weakly coupled ferrimagnetic mixed-spin chains. It is confirmed that the results obtained are consistent with the experiments for the quasi-one-dimensional Haldane compounds ${R}_{2}{\mathrm{BaNiO}}_{5}.$ We investigate the zero-temperature and the finite-temperature properties of the two-dimensional antiferromagnetic quantum spin system composed of the $s=1/2$ and $s=1$ spins. The spin excitation spectrum as well as the thermodynamic quantities are computed by means of the Schwinger-boson mean-field theory. We discuss how the magnetic double structure with the gapful and the gapless excitations is generated, and apply the results systematically to the Haldane gap system in a staggered magnetic field and also to the weakly coupled ferrimagnetic mixed-spin chains. It is confirmed that the results obtained are consistent with the experiments for the quasi-one-dimensional Haldane compounds ${R}_{2}{\mathrm{BaNiO}}_{5}.$

arXiv:cond-mat/0003252Physical review. B, Condensed matterJun 1, 200026 citations

LOW-LYING EXCITATIONS IN SPIN-PEIERLS SYSTEM WITH QUANTUM LATTICE DYNAMICAL EFFECT

Jing Xu, Zhiguo Wang, Yunlong Shi +2 more

In the continuum limit, we map a Heisenberg chain model, in which the spins are explicitly coupled to the lattice degrees of freedom, to one-dimensional quantum sine-Gorden model, and obtain the phase diagram and excitation spectrum of the system. The effect of quantum lattice fluctuation on the ground-state properties of the system is discussed in detail. The results show that a quantum phase transition from a gapless state to gapped dimerized phase occurs at nonzero value of the spin-phonon coupling. Moreover, our results indicate that the two-magnon excitation spectrum is more sensitive to the spin-phonon coupling than the one-magnon excitation spectrum.In the continuum limit, we map a Heisenberg chain model, in which the spins are explicitly coupled to the lattice degrees of freedom, to one-dimensional quantum sine-Gorden model, and obtain the phase diagram and excitation spectrum of the system. The effect of quantum lattice fluctuation on the ground-state properties of the system is discussed in detail. The results show that a quantum phase transition from a gapless state to gapped dimerized phase occurs at nonzero value of the spin-phonon coupling. Moreover, our results indicate that the two-magnon excitation spectrum is more sensitive to the spin-phonon coupling than the one-magnon excitation spectrum.

International Journal of Modern Physics BApr 4, 20060 citations

Dynamical properties in low-dimensional quantum spin systems

貴則杉本

Jan 1, 20120 citations

{1/T}_{1}.

We discuss the critical properties of

{1/T}_{1}

around plateaus and cusps in the magnetization curve.

We investigate the zero-temperature and the finite-temperature properties of the two-dimensional antiferromagnetic quantum spin system composed of the

s=1/2

and

s=1

spins. The spin excitation spectrum as well as the thermodynamic quantities are computed by means of the Schwinger-boson mean-field theory. We discuss how the magnetic double structure with the gapful and the gapless excitations is generated, and apply the results systematically to the Haldane gap system in a staggered magnetic field and also to the weakly coupled ferrimagnetic mixed-spin chains. It is confirmed that the results obtained are consistent with the experiments for the quasi-one-dimensional Haldane compounds

{R}_{2}{\mathrm{BaNiO}}_{5}.