主讲人：邵灿 副教授（南京理工大学）

题目：Topological phase transitions in the interacting Haldane model

时间：2024年01月21日（周日）下午15：00

地点：理工楼1215

联系人：罗洪刚、陆汉涛

报告摘要：

We investigate the ground-state phase diagram of the spinful extended Haldane-Hubbard model on the honeycomb lattice using an exact-diagonalization (ED), mean-field (MF) approach, and further complement it with the infinite density matrix renormalization group (iDMRG), applied to an infinite honeycomb cylinder. This model, governed by both on-site and nearest-neighbor interactions, can result in two types of insulators with finite local order parameters, either with spin or charge ordering. A third one, a topologically nontrivial insulator with nonlocal order is manifest in ED results. However, this state can not been observed in MF and iDMRG. Our study highlights how finite-size effects may result in misleading conclusions on the coexistence of finite local order parameters and nontrivial topology in this model.

We further revisit the ground-state phase diagram of the Haldane-Hubbard model on the honeycomb lattice with staggered sublattice potentials. The phase diagram includes the band insulator, Mott insulator, and two Chern insulator phases with Chern numbers C = 2 and C = 1, respectively. The character of transitions between different phases is studied by analyzing the lower-lying energy levels, excitation gaps, structure factors, and fidelity metric. We find that the C = 1 phase can be continuously deformed into the C = 2 phase without a gap closure in the periodic boundary condition, while a further analysis on the Berry curvatures indicates that the excitation gap closes at the phase boundary in a twisted boundary condition, accompanied by the discontinuities of structure factors. All the other phase transitions are found to be first-order ones as expected.

参考文献：

[1]H. Yuan, Y. Guo, R. Lu , H. Lu, and C. Shao, Phys. Rev. B 107, 075150 (2023).

[2]C. Shao, E. V. Castro, S. Hu, and R. Mondaini, Phys. Rev. B 103, 035125 (2021).

个人简介：

邵灿2012年本科毕业于兰州大学物理科学与技术学院，同年进入兰州大学交叉学科中心跟随罗洪刚教授和陆汉涛教授从事强关联电子体系中非平衡动力学的研究，并于2017年获得博士学位。随后，他在北京计算科学研究中心从事博士后研究工作，主要从事强关联拓扑体系平衡和非平衡态的研究，2020年博士后出站进入南京理工大学，工作至今。