报告摘要：

In a 3D solid, the low energy excitation of the linearly dispersive crossing bands satisfies the Dirac (Weyl) equation. Such band crossing is named as Dirac (Weyl) node (DN or WN), and such solid is known as the topological (Dirac or Weyl) semimetal (DSM or WSM), which exhibit remarkable features, such as Fermi arcs, magnetic monopoles and Weyl anomaly. In this talk, I will introduce three works on magnetic topological semimetals. 1. Ferromagnetic HgCr₂Se₄, the only known of double-Weyl semimetal, where the quantum anomalous Hall effect can be achieved in its quantum-well structure. 2. The long-pursuing ideal WSM realized in the non-collinear magnetic GdSI. We demonstrate that fruitful topological phases can be realized in a specific honeycomb lattice, including the ideal Weyl semimetal, double-Weyl semimetal, 3D strong topological insulator, nodal-line semimetal, and a novel semimetal consisting of both Weyl nodes and nodal-lines. 3. Anti-ferromagnetic (AFM) DSM realized in the interlayer AFM EuCd₂As₂. In this work, we generalize the concept of DSM to the magnetic space groups (MSGs), and define a new category of DSM in type IV MSGs. Many exotic topological states, such as the triple point semimetal and the AFM topological insulator holding of the half-quantum Hall effect can be derived from such AFM DSMs by breaking certain symmetry, providing an ideal platform to study topological phase transitions.

报告人简介：

　　徐刚， 2010年获中国科学院物理研究所博士学位，2010-2012年任中科院物理所助理研究员，2012-2016在美国斯坦福大学做访问研究，现在华中科技大学国家脉冲强磁场中心工作。主要从事新奇物性和材料的第一性原理计算和理论研究。研究兴趣包括：强关联与非常规超导、拓扑物质态，新型二维功能材料等，已发表学术论文36篇，总引用4500多次， H因子22；其中Nature子刊、PRL等国际顶级期刊16篇，另有两篇论文入选“2008年中国百篇最具影响国际学术论文”。重要成果：1）成功预言了铁基超导母体材料中的条纹状反铁磁基态——铁基超导获得"国家自然科学一等奖"的代表性工作之一2）把凝聚态中电子态按照拓扑分类的概念从绝缘体推广到了半金属，首先提出双外尔半金属的概念，开启了凝聚态中Weyl费米子的研究热潮，引用达650多次。