Kitaev spin-1/2 materials on the honeycomb lattice are a class of candidate materials that can potentially be used for realizing topological quantum computations. Existing Kitaev materials exhibit magnetic orders at low temperatures, including zigzag, counter-rotating spiral, and triple-Q orders, among others. In this talk, I will discuss our recent progress in understanding the magnetic orders in Kitaev materials using a coupled-chain analysis. In the first part of the talk, I will start with a single spin-1/2 Kitaev-Gamma chain and show that an extended gapless phase with an emergent SU(2)1 symmetry exists. Using this as a perturbative starting point, we studied the Kitaev-Heisenberg-Gamma chain and found a gapless phase and a ferromagnetic phase. In the second part, I will describe how we extended these 1D findings to 2D by connecting 1D chains together and treating the interchain interactions in a self-consistent mean field approach. The coupled-chain method successfully explains the zigzag order in alpha-RuCl3 and Na2IrO3, as well as the counter-rotating spiral order in alpha-Li2IrO3, based on the nearest-neighboring Kitaev-Heisenberg-Gamma model without requiring more complex interactions. In addition, a quantum critical point at (K=-1.68Γ<0,J>0) is found where five different magnetically ordered phases meet. 

Biography

杨望，现任南开大学物理学院教授。2018至2023年在不列颠哥伦比亚大学物理系做博士后，2018年于加州大学圣地亚哥分校获博士学位，2012年获清华大学学士学位。研究领域为凝聚态强关联物理及量子计算，包括一维强关联系统、量子可积模型中的动力学、基于测量的量子计算、非常规超导体等。

Inviter: Chu-Shun Tian