时间：2015年12月30日（星期三）下午3:00
地点：新物理楼5楼多功能厅
报告人：孟子杨研究员（中国科学院物理研究所）
摘要：
It is expected that the interplay between non-trivial band topology and strong electron correlation will lead to very rich physics. Thus a controlled study of the competition between topology and correlation is of great interest. Here, employing large-scale quantum Monte Carlo simulations, I will introduce a concrete example of the Kane-Mele-Hubbard model on an AA stacking bilayer honeycomb lattice with inter-layer antiferromagnetic interaction. Our simulations identified three different phases: a quantum spin-Hall insulator (QSH), a xy-plane antiferromagnetic Mott insulator and an inter-layer dimer-singlet insulator. Most importantly, an exotic topological phase transition between the QSH and the dimer-singlet insulators, purely driven by the inter-layer antiferromagnetic interaction is found. At the transition, the spin and charge gap of the system close while the single-particle excitations remain gapped, which renders this transition no mean field analogue and a transition between bosonic SPT states. This transition is described by a (2+1)d O(4) nonlinear sigma model with exact SO(4) symmetry, and a topological term at exactly Theta=Pi. I will also discuss a new, general technique -- strange correlator -- that we have developed to directly monitor the edge states of topological insulators in the presence of interaction. Relevance of these works towards more general interacting symmetry protected topological states will be discussed.
References:
1. Phys. Rev. B 92, 165123 (2015)
2. http://arxiv.org/abs/1508.06389
3. http://arxiv.org/abs/1510.07816
4. http://arxiv.org/abs/1512.02080
报告人简介：中国科学院物理研究所研究员、博士生导师。2005年获中国科学技术大学物理学学士学位，先后于2008年和2011年获德国斯图加特大学物理学硕士、博士学位。2011年至2014年间，先后在路易斯安那州立大学和多伦多大学从事博士后研究工作。2014年至今任职于中国科学院物理研究所。主要从事凝聚态物理中强关联电子系统的理论研究，具体的方法是通过在超级计算机上编写并运行大尺度的并行计算程序，用以量子特卡洛（Quantum Monte Carlo）和团簇动力学平均场（Cluster dynamic mean field）为代表的数值方法，精确地模拟自然界中很多复杂、却与现代科技息息相关的凝聚态物理系统。近年来在Nature发表第一作者文章1篇，Physical Review Letters发表文章5篇，Physical Review B Editors’ suggestion 2篇,Physical Review B Rapid Communications2篇，另有20多篇专业物理学刊物文章,到目前为止被引用次数超过800次。
邀请人：王宇副教授
