Afanasiev Dmytro, Hortensius Jorrit R, Matthiesen Mattias, Mañas-Valero Samuel, Šiškins Makars, Lee Martin, Lesne Edouard, van der Zant Herre S J, Steeneken Peter G, Ivanov Boris A, Coronado Eugenio, Caviglia Andrea D
Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, Netherlands.
Department of Physics, University of Regensburg, Regensburg, Germany.
Sci Adv. 2021 Jun 2;7(23). doi: 10.1126/sciadv.abf3096. Print 2021 Jun.
Van der Waals magnets provide an ideal playground to explore the fundamentals of low-dimensional magnetism and open opportunities for ultrathin spin-processing devices. The Mermin-Wagner theorem dictates that as in reduced dimensions isotropic spin interactions cannot retain long-range correlations, the long-range spin order is stabilized by magnetic anisotropy. Here, using ultrashort pulses of light, we control magnetic anisotropy in the two-dimensional van der Waals antiferromagnet NiPS Tuning the photon energy in resonance with an orbital transition between crystal field split levels of the nickel ions, we demonstrate the selective activation of a subterahertz magnon mode with markedly two-dimensional behavior. The pump polarization control of the magnon amplitude confirms that the activation is governed by the photoinduced magnetic anisotropy axis emerging in response to photoexcitation of ground state electrons to states with a lower orbital symmetry. Our results establish pumping of orbital resonances as a promising route for manipulating magnetic order in low-dimensional (anti)ferromagnets.
范德瓦尔斯磁体为探索低维磁性的基本原理提供了一个理想的平台，并为超薄自旋处理设备带来了机遇。默明-瓦格纳定理表明，在低维情况下，各向同性的自旋相互作用无法保持长程相关性，长程自旋序由磁各向异性稳定。在此，我们利用超短光脉冲，在二维范德瓦尔斯反铁磁体NiPS中控制磁各向异性。通过将光子能量调谐至与镍离子晶体场分裂能级之间的轨道跃迁共振，我们展示了具有显著二维行为的亚太赫兹磁振子模式的选择性激活。磁振子振幅的泵浦偏振控制证实，这种激活由光激发基态电子至具有较低轨道对称性的态时出现的光致磁各向异性轴所支配。我们的结果表明，泵浦轨道共振是操纵低维（反）铁磁体中磁序的一条有前景的途径。
