Abstract (WS-E, poster)

PS-E-1. Furuya, Shunsuke

1. Affiliation: Institute for Solid State Physics, University of Tokyo
2. Country: Japan
3. Participation: from 11/14 to 11/18 from 12/5 to 12/9
4. Keywords: low-dimensional quantum spin systems, electron spin resonance, frustrated systems
5. Title: Single-ion anisotropy of Haldane chains and form factor of O(3) nonlinear sigma model
   Abstract:
   We discuss the perturbative approach to Haldane chains with the single-ion anisotropy based on form factors of O(3) nonlinear sigma model. The single-ion anisotropy corresponds to the two-particle form factor of symmetric traceless tensor. This form factor is obtained explicitly for the first time with the aid of infinite time-evolving block decimation (iTEBD) method. We show that the two-particle form factor accurately determines the excitation gaps, dynamical structure factors, and electron spin resonance frequency shift.

PS-E-2. Morimoto, Takahiro

1. Affiliation: University of Tokyo, Department of Physics
2. Country: Japan
3. Participation: from 12/2 to 12/9
4. Keywords: graphene, quantum Hall effect, optical response, localization
5. Title: Two parameter flow diagram of the longitudinal and Hall conductivities in ac regime in the disordered graphene quantum Hall system
   Abstract:
   In the physics of graphene with its realization of a massless Dirac system at low energies, dynamical (ac) responses should be interesting. We have recently shown for the graphene integer quantum Hall effect (QHE) that the plateau structure is retained even in the ac Hall conductivity $\sigma_{xy}(\omega)$ in the $\omega \sim$ THz regime although the plateau height deviates from the quantized values in both the massless Dirac model [T. Morimoto, Y. Hatsugai and H. Aoki, Phys. Rev. Lett. 103, 116803 (2009).]. The plateau structure in the ac region is attributed to localization effect, as confirmed quantitatively from a dynamical scaling of the plateau-to-plateau transition width of $\sigma_{xy} (\omega)$ [T. Morimoto, Y. Avishai and H. Aoki, Phys. Rev. B 82, 081404(R) (2010). ]. Here we numerically study both longitudinal and Hall optical conductivities to discuss the scaling flow diagram for $\sigma_{xx}(\omega) - \sigma_{xy}(\omega) $, since the flow diagram in the static case is well-known to beautifully capture QHE as a fixed-point property but has never been examined in the ac regime. The result shows that the ac flow diagram is not significantly altered for the small-$\omega$ region. There, a fixed-point behavior emerges as in the dc case, which we interpret in terms of the dynamical scaling analysis.

PS-E-3. Nakata, Kouki

1. Affiliation: Kyoto University, YITP
2. Country: Japan
3. Participation: from 11/7 to 12/9
4. Keywords: spin current, spin pumping effects, magnon, spintronics,
5. Title: Spin currents carried by magnons in metals and insulators
   Abstract:
   The magnon pumping effects in ferromagnetic insulators under an external time-dependent transverse magnetic field is theoretically studied. The magnon source term has a resonance structure as a function of the angular frequency of the transverse field, and this fact is useful to enhance the pumping effects. We are going to show that this magnon pumping effect occurs in metals as well as in insulators. Moreover thermal properties of spin currents in insulators would be presented.

PS-E-4. Sakano, Rui

1. Affiliation: Department of Applied Physics, University of Tokyo
2. Country: Japan
3. Participation: from 11/7 to 12/9
4. Keywords: quantum dot, Kondo correlation, nonequilibrium current, noise
5. Title: Nonequilibrium current in orbital-degenerated Anderson dot with a Hund rule's coupling
   Abstract:
   Recently, theoretical study on nonequilibrium current due to the Kondo correlation in a quantum dot has predicted enhancement of shot noise with a fractional Fano factor and have stimulated subsequent experimental study. Full counting statistics for Kondo dots clarified that the nonequilibrium scattering current is composed of two type of electron transfer due to a single quasiparticle and a pair of quasiparticle in singlet state, and these electron transfers give the nontrivial Fano factor. We analyze full counting statistics for nonequilibrium current in a quantum dot described by an orbital-degenerated Anderson model with a Hund rule's coupling, using renormalized perturbation theory. Increase of orbital degeneracy suppresses the Kondo correlation and reduces number of paired quasiparticles in current, while increase of Hund rule's coupling or decrease of inter-orbital Coulomb repulsion enhance them. This clearly reflects on parameter dependence of cumulants and cross-correlations of nonequilibrium current.

PS-E-5. Wakutsu, Takeo

1. Affiliation: Department of Physics, Tokyo Institute of Technology
2. Country: Japan
3. Participation: from 12/6 to 12/8
4. Keywords: graphene
5. Title: Optical and inter layer conductivities of multilayer graphenes
   Abstract:
   We discuss optical and inter layer conductivities of multilayer graphenes with various stacking structures. In order to calculate them, we investigate the electronic structure of multilayer graphenes. We find that their properties greatly depend on stacking orders.

PS-E-6. Wang, Zheng-yuan

1. Affiliation: Department of Physics, Tokyo Institute of Technology
2. Country: Japan
3. Participation: from 12/6 to 12/8
4. Keywords:
5. Title: Spin-chain description of fractional quantum Hall states
   Abstract:
   We discuss relationship between the fractional quantum Hall (FQH) effect in the vicinity of the thin-torus, a.k.a. Tao-Thouless (TT), limit and quantum spin chains. By extending the approach introduced in previous work to study a truncated Hamiltonian beyond the TT limit, we map FQH states with filling factors at m = 1 Jain sequences p/(2p + 1) in the lowest Landau level to S = 1 effective spin chains with p spins in each unit cell. We verify the decrement of energy gap for both FQH systems and the corresponding spin chains, and obtain the correlation functions for the effective spin chains with numerical simulatuion. We point out the correlation length of these effective spin chains increase with p, which yields the decrement of the mass gap.