报告人：北京师范大学 郭文安 教授

报告题目：Emergent topological and fractional excitations in a two-dimensional valence-bond solid

时间：2015年9月30日星期三上午9点30分

地点：物理馆323室

报告摘要：The Valence-bond solid (VBS) is one of the non-trivial non-magnetic ground state which plays an essential role in the study of the deconfined quantum criticality violating the standard Landau-Ginzburg-Wilson framework.  Spinons are emergent fractional excitations, which bind together in the VBS state, but deconfine at the critical point separating the VBS from the antiferromagnetic Neel state.  Topological excitations can also arise in the VBS state, although topological order has mainly been discussed in the context of exotic states without any long-range order such as quantum spin liquids.  In this talk, I will present our recent projector quantum Monte Carlo studies of the emergent topological excitations and the mechanism of the confinement/deconfinement of spinons (holons) in the $J-Q$ model on the two-dimensional square lattice, which has valence-bond solid order in its ground state.  A brief introduction to the projector quantum Monte Carlo method for quantum spin models will also be included.}
%\talkspeaker{Wenan Guo received his M.Sc.\ from the Lanzhou University in 1993 and his PhD from the Beijing Normal University in 1996.  He did his postdoc research at the Delft university of technology in 1997-1998.  Since 2004 he has been a professor at Beijing Normal University.  His main research interests are in quantum and classical many-body physics, where he uses numerical methods to study both quantum and thermal phase transitions in various statistical models.