Recently, ferromagnetic/nonmagnetic heavy metal heterostructures have been intensively investigated as terahertz (THz) emitters. The interconversion of spin-to-charge dynamics plays a central role for efficient emission of THz electromagnetic pulses. However, a direct observation of spin–charge interconversion in antiferromagnetic (AFM) materials occurring on the sub-picosecond time scale remains a challenge. Herein, the magnetic-field-, pump-fluence-, and polarization-dependent THz emission behaviors by a femtosecond optical pump in cobalt (Co)/Mn₂Au nanometer heterostructure are experimentally investigated. The Co/Mn₂Au bilayer generates sizable THz signals, whereas the Mn₂Au/Pt bilayer does not show any THz emission. In addition, the thickness- and temperature-dependent THz emission measurements indicate a direct relation between the THz amplitude and the conductivity of AFM Mn₂Au layer. The results obtained will not only promote the fundamental understanding of ultrafast spin–charge interconversion in Co/Mn₂Au heterostructures, but also provide a possibility of spectroscopic-based spin current detector at THz-frequency range.

中文翻译：

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Co/Mn2Au 自旋电子双层的温度相关太赫兹发射

最近，铁磁/非磁重金属异质结构作为太赫兹 (THz) 发射器得到了深入研究。自旋到电荷动力学的相互转换对于有效发射太赫兹电磁脉冲起着核心作用。然而，在亚皮秒时间尺度上直接观察反铁磁（AFM）材料中的自旋电荷相互转换仍然是一个挑战。在此，通过实验研究了钴 (Co)/Mn ₂ Au 纳米异质结构中飞秒光泵的磁场、泵浦通量和偏振相关的太赫兹发射行为。Co/Mn ₂ Au 双层产生相当大的 THz 信号，而 Mn ₂Au/Pt 双层不显示任何太赫兹发射。此外，与厚度和温度相关的太赫兹发射测量表明太赫兹振幅与 AFM Mn ₂ Au 层的电导率之间存在直接关系。所获得的结果不仅将促进对 Co/Mn ₂ Au 异质结构中超快自旋 - 电荷互变的基本理解，而且还为在太赫兹频率范围内基于光谱的自旋电流检测器提供了可能性。