Interaction and spin–orbit effects on a kagome lattice at 1/3 filling

We investigate the competing effects of spin-orbit coupling and electron--electron interaction on a kagome lattice at 1/3 filling. We apply the cellular dynamical mean-field theory and its real-space extension combined with the continuous time quantum Monte Carlo method, and obtain a phase diagram including the effects of the interaction and the spin-orbit coupling at T = 0. 1t, where T is the temperature and t is the hopping energy. We find that without the spin-orbit coupling, the system is in a semi-metal phase stable against the electron--electron interaction. The presence of the spin-orbit coupling can induce a topological non-trivial gap and drive the system to a topological insulator, and as the interaction increases, a larger spin--orbit coupling is required to reach the topological insulating phase.     

Quantum phase transitions in two-dimensional strongly correlated fermion systems

In this article, we review our recent work on quantum phase transition in two-dimensional strongly correlated fermion systems. We discuss the metal−insulator transition properties of these systems by calculating the density of states, double occupancy, and Fermi surface evolution using a combination of the cellular dynamical mean-field theory (CDMFT) and the continuous-time quantum Monte Carlo algorithm. Furthermore, we explore the magnetic properties of each state by defining magnetic order parameters. Rich phase diagrams with many intriguing quantum states, including antiferromagnetic metal, paramagnetic metal, Kondo metal, and ferromagnetic insulator, were found for the two-dimensional lattices with strongly correlated fermions. We believe that our results would lead to a better understanding of the properties of real materials.     

Mn 位 Al 掺杂的六角结构 YMn1-xAlxO3(0≤x ≤0.1)单晶的磁性及受挫调制

用光学浮区法生长了 Mn 位 Al 掺杂的六角结构 YMn1 -x Alx O3 系列单晶样品, 对该样品的掺杂效应及磁受挫性质进行了研究. 结果发现, 在 YMnO3 的 Mn3 + 位掺入不同浓度的非磁性 Al3 + 离子对样品的磁化特性有很大的影响. 随着掺杂浓度的增加, 居里-外斯温度明显降低, 磁性受挫因子f 减小, 反铁磁转变温度向低温方向移动.由于 Al3 + 离子半径比 Mn3 + 小, 掺杂使得系统的晶格常数变小, Mn-Mn 键长变短, 最终导致交换积分减小. 另外, 由于非磁性的 Al3 + 离子部分替代 Mn3 + 离子直接破坏了 Mn3 + 离子间的交换路径, 结果使得体系的几何受挫被抑制,反铁磁转变温度降低, Mn3 + - Mn3 + 之间的 AFM 相互作用被大大削弱.