电磁辐射的起源从Spintronic Terahertz发射器:一个时间依赖密度函数理论加上Jefimenko方程方法
Ali Kefayati1, Branislav K Nikolić1
1Department of Physics and Astronomy, <a href="https://ror.org/01sbq1a82">University of Delaware</a>, Newark, Delaware 19716, USA.
Physical review letters
|October 11, 2024
概括
电荷电流,而不是磁辐射,在自旋发射器中产生太赫兹 (THz) 电磁场. 这项研究揭示了通过去磁化送的电荷电流主导了THz发射,即使没有旋转轨道合效应.
科学领域:
- 凝聚物质物理学 凝聚物质物理学
- 材料科学 材料科学 材料科学
- 量子电动力学 量子电动力学
背景情况:
- 对于超高速技术至关重要的螺旋式太赫兹 (THz) 发射器,通过复杂的微观过程产生电磁辐射.
- 激光驱动磁性材料中电荷电流和电磁辐射的精确起源,尽管经过了数十年的研究,但仍然不明确.
- 现有的模型往往过度强调磁双极辐射,忽视了电荷电流的主导作用.
研究的目的:
- 开发和应用一个第一原则的方法来计算微观的电荷电流和电磁辐射在spintronic THz发射器.
- 为了阐明导致秒激光驱动磁性材料中THz发射的主导机制.
- 量化光到THz辐射转换的效率和角分布.
主要方法:
- 实时时间依赖密度函数理论 (TD-DFT) 模拟电荷和电流密度动态.
- 杰菲门科方程,包括延迟电位,用于解决电磁场的麦克斯韦方程.
- 时间依赖项的富里埃转换来分析频率依赖辐射贡献 (0.1-30 THz).
主要成果:
- 在Ni层中的电磁辐射主要是由在去磁化过程中送的电荷电流驱动的,而不是磁双极辐射.
- 这种充电电流机制不需要通过旋转轨道合 (SOC) 进行旋转到充电的转换.
- 在Ni/Pt双层中,THz排放主要由Ni层中的电荷电流占据主导地位,SOC驱动的Pt中旋转到电荷转换的贡献较小.
结论:
- 通过去磁化产生电荷电流是研究的自旋电子系统中THz辐射的主要来源.
- 开发的第一原则方法为了解THz排放机制提供了一个强大的框架.
- 这项工作澄清了基本物理,并指导了更高效的自旋电子THz发射器的设计.
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