南方科技大学刘奇航教授讲座通知

受科学与工业技术研究院资助,应化工与化学学院姚远副教授和理学院物理系李伟奇副教授的邀请,南方科技大学物理系刘奇航副教授来校进行学术交流,并将于2018815日进行学术讲座,欢迎全校感兴趣的师生参加。

刘奇航是南方科技大学及深圳市量子科学与工程研究所双聘教授,博士生导师。2003-2012年间在北京大学物理学院学习,取得本科及博士学位,随后在美国西北大学从事博士后研究(合作导师Arthur Freeman教授),在科罗拉多大学博尔德分校任助理研究员(合作导师Alex Zunger教授)。主要从事以密度泛函理论为主的凝聚态理论研究,聚焦真实材料的新奇物理性质。研究兴趣包括理解材料中新奇的电学,磁学,光学,缺陷,自旋极化,拓扑等性质及它们的耦合,以及功能导向的新型材料设计及预测,相关研究成果以第一作者或通讯作者身份发表在Nat. Phys.Phys. Rev. XPhys, Rev. Lett.Nano Lett.Adv. Funct. Mater.等国际权威期刊上,总计发表学术论文30余篇,Google Scholar引用超过2200次;多次在国际学术会议及高校论坛做邀请报告,担任PRLNano Lett.Adv. Mater. 等高水平期刊审稿人。

讲座安排:

题目:Hidden spin polarization in materials with inversion symmetry

时间:2018815 10:00

地点:理学楼308

摘要:Spin polarization in nonmagnetic materials is a textbook effect associated with spin-orbit coupling and the global absence of inversion symmetry. We note, however, that the relativistic spin-orbit interaction is anchored primarily on atomic nuclear sites and should thus be primarily sensitive to site point-group asymmetries, rather than bulk space-group crystal asymmetry. In centrosymetric crystals the spin bands are degenerate in E vs k momentum space, but this does not mean that the spins are mixed in position space. In contrast, we find and validate via first-principles calculations that in centrosymmetric materials with non-centrosymmetric site symmetries (such as MoS2, LaOBiS2, or Bi2Se3) there is a nonzero local spin polarization even though the total spin is zero. Such real-space spin-polarizations are normally hidden by compensation effect, rather than being intrinsically absent, and are already verified by upcoming experiments.

This understanding leads to the recognition that a previously overlooked hidden form of spin polarization should exist in a much broader class of 3D bulk solids that own global inversion symmetry, and thus open the possibility to provide new routines for manipulating electron spins. The concept of hidden spin polarization also explains many previously embarrassing observations of apparent polarization noted in centrosymmetric systems that by common understanding should not have existed.

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