极性反铁磁体Fe2Mo3O8的太赫兹发射谱  

Terahertz emission spectrum of polar antiferromagnet Fe2Mo3O8

作　　者：时立宇 吴东 王子潇 林桐 张思捷 刘巧梅 胡天晨 董涛 王楠林 Shi Li-Yu;Wu Dong;Wang Zi-Xiao;Lin Tong;Zhang Si-Jie;Liu Qiao-Mei;Hu Tian-Chen;Dong Tao;Wang Nan-Lin(International Center for Quantum Materials,School of Physics,Peking University,Beijing 100871,China)

机构地区：[1]北京大学物理学院,量子材料科学中心,北京100871

出　　处：《物理学报》2020年第20期90-95,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11888101);国家重点基础研究发展计划(批准号:2017YFA0302904,2016YFA0300902)资助的课题.

摘　　要：极性材料中,电子受激发跃迁会改变材料的电极化矢量,受到飞秒脉冲激光的激发时,瞬态变化的电极化矢量会向外辐射电磁波,产生太赫兹波段的发射谱.在磁有序体系中,受到相干激发的自旋波在进动弛豫的过程中,会辐射相同频率的电磁波.研究这些材料的太赫兹发射谱,不仅有助于理解材料的铁电有序和磁有序的动力学过程,也为寻找新的太赫兹源提供参考.我们对极性反铁磁体Fe2Mo3O8的太赫兹发射谱进行了研究,在800 nm飞秒激光的泵浦下,材料中的电子发生跨越能隙的激发,对电极化矢量产生超快调制,观察到0.1—3.5 THz的宽带太赫兹激发谱,太赫兹电场方向沿材料的固有电极化方向.在进入磁有序后,观测到两个新的单频太赫兹震荡,分别位于1.25和2.70 THz,分别对应Fe2Mo3O8的两个反铁磁自旋波.In polar materials,the transition of electrons in momentum space will change the spontaneous polarization.When excited by femtosecond pulse laser,the transient modulation of the electric polarization will radiate electromagnetic wave at terahertz frequency.In a magnetic ordered system,the coherent excited spin wave radiates electromagnetic waves of the same frequency in the process of precession and relaxation.The investigation of the terahertz emission spectra of these materials not only helps us to understand the ferroelectric and magnetic ordered dynamic processes of materials,but also provides a reference for searching for new terahertz sources.We study the terahertz emission spectrum of the polar antiferromagnet Fe2Mo3O8.Under the pumping of 800 nm laser,electrons in the material are excited across the band gap leading the electric polarization to be ultra-fast modulated.The broadband terahertz excitation spectrum from 0.1 to 3.5 THz is observed,and the direction of the terahertz electric field is along the inherent electric polarization direction of the material.After entering into the magnetic order state,two new single-frequency terahertz oscillations are observed,located at 1.25 THz and 2.7 THz respectively,which correspond to the excitation of the two antiferromagnetic spin waves of Fe2Mo3O8.

关 键 词：Fe2Mo3O8 极性反铁磁体 太赫兹发射谱 

分 类 号：O441.4[理学—电磁学] O482.525[理学—物理]