The Z2 topological invariant, spin Chern number and zero-frequency Green's functions in correlated topological insulators

Title: The Z2 topological invariant, spin Chern number and zero-frequency Green's functions in correlated topological insulators Speaker: Hsiang-Hsuan Hung 时间: 2013年7月18日（周四）下午4:00 地点: 理科五号楼607会议室联系人: niuqian811@yahoo.com 牛谦 Abstract: The stability of topological insulators with electron-electron correlation have been central topics yet elusive to solve. In this talk, we will discuss the correlation effects in the two descendants of the Kane-Mele-Hubbard model, called generalized Kane-Mele-Hubbard model (GKM) and dimerized Kane-Mele-Hubbard model (DKM), by means of the unbiased Quantum Monte Carlo (QMC) method. In the noninteracting limit, both models undergo topological phase transitions by tuning tight-binding parameters. With interaction, we can accurately evaluate the Z2 invariant and spin Chern number to identify the phase transition in finite-size clusters with the QMC. It is found that the quantum fluctuations from interaction stabilizes thetopological insulator phase in the GKM model, but destabilizes the topological phase in the DKM model. In addition to the topological invariants, We also identify qualitative features of the zero-frequency Green's function which are computationally useful. About the speaker: Dr. Hsiang-Hsuan Hung received his Physics PhD at the University of California, San Diego in 2011. Then he spent a year at the University of Illinois at Urbana-Champaign. In 2012, he moved to the University of Texas at Austin as a postdoc fellow. His current research interests include strongly correlated systems and topological materials, by means of numerical methods, like quantum Monte Carlo and dynamical mean field theory.