Abstract (WS-C, poster)

Shiozaki, Ken

1. Affiliation: Department of Physics, Kyoto University
2. Country: Japan
3. Participation: from 11/7 to 12/9
4. Keywords: topological insulator
5. Title: The condition for the existence the gapless modes in topological defects from Green's functions
   Abstract:
   Recently the conditions for the existence of gapless modes in arbitrary topological defects in insulators and superconductors are proposed. [Jeffrey C.Y. Teo and C.L. Kane, Phys. Rev. B 82, 115120 (2010).] It is suggested that the existence of gapless modes follows from topologically nontrivial Hamiltonian which varies with adiabatic material-parameters surrouding the defects. In this study, we discuss an expansion of the earlier work in terms of Green's functions.

Shitade, Atsuo

1. Affiliation: University of Tokyo
2. Country: Japan
3. Participation: from 11/21 to 11/25 from 12/5 to 12/9
4. Keywords: anomalous Hall effect, topological insulators
5. Title: Scaling in intrinsic and extrinsic anomalous Hall effects
   Abstract:
   We numerically study the minimal model of the anomalous Hall effect which exhibits the intrinsic and extrinsic mechanisms by changing the impurity content. We discuss the effects of finite temperature and phenomenological quasiparticle damping on these two mechanisms. Scaling relations experimentally proposed is obtained.

Takenaka, Yuto

1. Affiliation: Department of Physics, Kyoto University
2. Country: Japan
3. Participation: from 11/7 to 12/9
4. Keywords: multi-orbital Mott transitions
5. Title: Variational Monte Carlo analysis of the Mott transition in multi band electron systems
   Abstract:
   Recently, Mott transitions in multi-orbital systems have been investigated extensively. In these systems, Hund's coupling as well as inter- and intra-orbital Coulomb interactions plays important roles. To understand the effects of orbital degeneracy, it is necessary to study these effects systematically. In this study, we investigate a two-dimensional two-orbital Hubbard model on a square lattice at half filling. Applying the variational Monte Carlo (VMC) method, we address the Mott transitions in two-orbital systems. As a variational trial wave function, we consider Gutzwiller's on-site correlations and nearest-neighbor doublon-holon correlations. We calculate the ground-state energy and obtain the phase diagram at zero temperature. The momentum distribution and the structure factors are also calculated. From these data, we discuss how Hund's coupling affects the Mott transitions in multi-orbital systems.

Tsuchiizu, Masahisa

1. Affiliation: Department of Physics, Nagoya University
2. Country: Japan
3. Participation: from 11/14 to 11/25
4. Keywords: intra-molecular charge ordering, ab initio calculation
5. Title: Ab initio derivation of multi-orbital extended Hubbard model for molecular crystals
   Abstract:
   We derive an effective two-orbital extended Hubbard model of the molecular compounds (TTM-TTP)I3 and [Au(tmdt)2], by using configuration-interaction (CI) ab initio calculations. Model parameters are determined so as to reproduce the CI Hamiltonian matrix and we analyze the band structure to confirm the multi-orbital feature. Furthermore, we derive the effective model based on the fragment molecular orbitals and it can successfully describe experimentally-speculated intramolecular charge ordering in (TTM-TTP)I3.

Yoshida, Tsuneya

1. Affiliation: Department of Physics, Kyoto University
2. Country: Japan
3. Participation: from 11/7 to 12/9
4. Keywords: correlated topological insulator
5. Title: DMFT study of correlated topological insulators
   Abstract:
   Tsuneya Yoshida, Satoshi Fujimoto, and Norio Kawakami
   Department of Physics, Kyoto University, Kyoto 606-8502, Japan
   In these days, topological insulators have attracted much attention as a new field of condensed matter physics. These insulators have odd number of gapless edge states which are robust against the non-magnetic impurity due to time reversal symmetry. More recently, the study of correlation effects on topological band insulators (TBI) is one of the intriguing issues in studies of topological insulators. One of the reasons is that some of iridium oxides, such as $\mathrm{Na_2IrO_3}$ and $\mathrm{A_2Ir_3O_7} \hspace{2mm}(\mathrm{A=Pr,Eu})$, are proposed as the candidate of a topological insulator due to strong spin-orbit interaction of iridium sites [1]. Up to now, several studies of correlation effect on topological phases have been done. In these studies, competition between AF phase and TBI phase and competition between charge-density-wave (CDW) phase and TBI phase are clarified [2]. In spite of these numerous studies, there are several unclear points. For example, if local coulomb interaction is strong, the system is expected to change into Mott insulator (MI). There are several studies of this phase competition. However, the studies are still in mean field level. The goal of our study is to clarify how the TBI changes into MI beyond mean field analysis. We are going to analyze on-site interaction effect on the Kane-Mele model [3] and the Bernevig-Hughes-Zhang model [4]. Both of these two models have complex hopping term due to the spin-orbit interaction. The lattice structures of each models are, respectively, honeycomb lattice and two-orbital square lattice. As the method of our analysis, we employ the dynamical mean field theory (DMFT) combined with continuous-time quantum Monte Carlo (CT-QMC). We analyze the phase competition with the behavior of the spin Hall conductivity characterizing TBI. We will report these results in our poster.
   [1]A. Shitade \textit{et al.}, Phys. Rev. Lett. \textbf{102}, 256403 (2009).
   [2]Z. Cai \textit{et al.}, Phys. Rev. B \textbf{78}, 035123 (2008); M. Hohenadler \textit{et al.}, Phys. Rev. Lett. \textbf{106}, 100403 (2011).
   [3]C. L. Kane \textit{et al.}, Phys. Rev. Lett. \textbf{95}, 146802 (2005).
   [4]B. A. Bernevig \textit{et al.}, Science \textbf{314}, 1757 (2006).