Liu Peiwen, Eckberg Chris, Pan Lei, Zhang Peng, Wang Kang L, Lüpke Gunter
Department of Applied Science, The College of William and Mary, Williamsburg, VA, 23187, USA.
Department of Electrical Engineering, University of California, Los Angeles, CA, 90095, USA.
Sci Rep. 2022 Jul 15;12(1):12117. doi: 10.1038/s41598-022-16205-3.
Optical control of the magnetic properties in topological insulator systems is an important step in applying these materials in ultrafast optoelectronic and spintronic schemes. In this work, we report the experimental observation of photo-induced magnetization dynamics in the magnetically doped topological insulator (MTI)/antiferromagnet (AFM) heterostructure composed of Cr-(Bi,Sb)Te/CrSb. Through proximity coupling to the AFM layer, the MTI displays a dramatically enhanced magnetism, with robust perpendicular magnetic anisotropy. When subjected to intense laser irradiation, both surface and bulk magnetism of the MTI are weakened by laser-induced heating of the lattice, however, at the surface, the deleterious heat effect is compensated by the strengthening of Dirac-hole-mediated exchange coupling as demonstrated by an unconventional pump-fluence-dependent exchange-bias effect. Through theoretical analyses, the sizes of exchange coupling energies are estimated in the MTI/AFM bilayer structure. The fundamentally different mechanisms supporting the surface and bulk magnetic order in MTIs allow a novel and distinctive photo-induced transient magnetic state with antiparallel spin configuration, which broadens the understanding of the magnetization dynamics of MTIs under ultrashort and intense optical excitation.
在拓扑绝缘体系统中对磁特性进行光学控制是将这些材料应用于超快光电子学和自旋电子学方案的重要一步。在这项工作中，我们报告了在由Cr-(Bi,Sb)Te/CrSb组成的磁性掺杂拓扑绝缘体（MTI）/反铁磁体（AFM）异质结构中光诱导磁化动力学的实验观察结果。通过与AFM层的近邻耦合，MTI表现出显著增强的磁性，并具有强大的垂直磁各向异性。当受到强激光照射时，MTI的表面和体磁都会因激光诱导的晶格加热而减弱，然而，在表面，有害的热效应通过狄拉克空穴介导的交换耦合增强得到补偿，这由非传统的泵浦通量依赖交换偏置效应证明。通过理论分析，估计了MTI/AFM双层结构中的交换耦合能大小。支撑MTIs中表面和体磁有序的根本不同机制允许一种具有反平行自旋构型的新颖独特的光诱导瞬态磁态，这拓宽了对MTIs在超短和强光激发下磁化动力学的理解。
