Speaker
Description
Symmetry theory of magnetic geometry
The physical properties in magnetic-ordered materials were ultimately believed to
rely on the symmetry theory of magnetic groups. Recently, it has come to light
that a more comprehensive group, known as spin (crystallographic) group, which
combines separate spin and spatial operations, is necessary to fully characterize
the geometry and underlying properties of magnetic-ordered materials such as al
termagnets [1]. In this talk, we introduce the recent developments of spin group
theory, including extensive enumeration of over 100000 spin space groups, iden
tification of spin groups for collinear, coplanar, and noncoplanar configurations,
and irreducible co-representations in momentum space leading to more energy
degeneracies that are disallowed by magnetic groups [2]. We further show some
theoretical and experimental results of spin group applications in understanding
the physical effects of unconventional magnetism beyond the framework of mag
netic groups [3,4].
Biography: 刘奇航，南方科技大学教授，本科及博士均毕业于北京大学物理学院，曾
在美国西北大学、科罗拉多大学博尔德分校进行博士后研究。主要从事计算凝聚态物
理研究，研究兴趣聚焦于量子材料中的对称性新理论与新效应，以及相关的新材料设
计筛选。发表SCI论文100余篇，H指数41。2018年作为独立PI后发表通讯作者文章
包括1篇Nature、14篇PRL/PRX、4篇Nat. Commun.、3篇Natl. Sci. Rev.等。2020年
作为项目负责人获批国家重点研发计划青年项目，2022年获批深圳市杰青项目，2024
年获广东省青年科技奖，2021至2024年连续入选斯坦福大学发布的全球前2%顶尖
科学家榜单（World’sTop2%Scientists）。2024 年起担任 npj Quantum Materials
副编辑。
References:
[1] Liu et al. Phys. Rev. X 12, 021016 (2022).
[2] Chen et al. Phys. Rev. X 14, 031038 (2024).
[3] Zhu et al. Nature 626, 523 (2024).
[4] Liu et al. Nat. Phys. in press (2024)
