题 目：Fractional magnetization plateau and spinon quantum spin Hall state in kagome antiferromagnets
报 告 人：何黎伟 博士
时 间：2024年12月28日 上午 10:30
地 点：物理学院 LE201
邀 请 人：胡自翔
报告摘要：The kagome lattice is an exceptional platform for exploring novel many-body states, owing to its distinctive lattice and electron structures. Motivated by very recent experimental observations of the 1/9-magnetization plateaus in YCu3(OH)6+xBr3−x and YCu3(OD)6+xBr3−x, our study delves into the magnetic-field-induced phase transitions in the nearest-neighbor antiferromagnetic Heisenberg model on the kagome lattice using the variational Monte Carlo technique. We uncover a phase transition from a zero-field Dirac spin liquid to a field-induced magnetically disordered phase that exhibits the 1/9-magnetization plateau. Through a comprehensive analysis encompassing the magnetization distribution, spin correlations, chiral order parameter, topological entanglement entropy, ground-state degeneracy, Chern number, and excitation spectrum, we pinpoint the phase associated with this magnetization plateau as a chiral Z3 topological quantum spin liquid and elucidate its diverse physical properties. As the magnetic field increases further, we also obtain a 1/3-magnetization VBS state.
Besides, we construct a spinon quantum spin Hall state in kagome antiferromagnets with an additional Dzyaloshinskii-Moriya interaction. This state is a gapped QSL sharing the analogous physical properties with quantum spin Hall state. In term of the category of topological order, it is an Abelian double-semion topological order (doubled Chern-Simons state or CSL+CSL-) described by a sum of two topological quantum field theories with opposite chiralities, which is suggested in string-net model.
References: Li-Wei He, et al., Phys. Rev. Lett. 133, 096501 (2024). Li-Wei He, et al., Phys. Rev. B 110, 035131 (2024).
报告人介绍：何黎伟，南京大学物理学院 2019级硕博连读生。师从李建新教授，以第一作者的身份在Physical Review Letters、Physical Review B等物理学高质量期刊上发表过论文数篇。曾获2024年研究生国家奖学金、优秀研究生标兵、2023年优秀研究生等荣誉称号。
