论文标题
光学近场中电子梁的自旋翻转
Spin flips of electron beams in optical near fields
论文作者
论文摘要
使用光的电子束的自旋极化是非常可取的，但极具挑战性，因为在先前使用自由空间光的研究中提出的方法通常需要巨大的激光强度。在这里，我们提出了在纳米结构上扩展的横向电气近场的使用，以通过利用相匹配的光学近距离磁场中的强非弹性电子散射来有效地诱导相邻的电子束的自旋翻转。我们的计算表明，使用短相互作用长度（$ 16 \，μ$ m）的使用大幅度降低激光强度（$ \ sim 10^{12} \，$ w/cm $^2 $）可实现大约$ 12 \％$的电子自旋flip概率。有趣的是，平行于与电场的非极化入射电子束的两个自旋成分是旋转的，并且无弹性地散落到不同的能量状态，从而提供了尾矿的类似物 - 能量尺寸的gerlach实验。我们的发现对于自由电子旋转的光学控制，自旋极化电子束的制备以及与材料科学和高能物理学一样多样的应用非常重要。
Manipulating the spin polarization of electron beams using light is highly desirable but exceedingly challenging, as the approaches proposed in previous studies using free-space light usually require enormous laser intensities. Here, we propose the use of a transverse electric optical near field, extended on nanostructures, to efficiently induce spin flips of an adjacent electron beam by exploiting the strong inelastic electron scattering in phase-matched optical near fields. Our calculations show that the use of a dramatically reduced laser intensity ($\sim 10^{12}\,$W/cm$^2$) with a short interaction length ($16\,μ$m) achieves an electron spin-flip probability of approximately $12\%$. Intriguingly, the two spin components of an unpolarized incident electron beam -- parallel and antiparallel to the electric field -- are spin-flipped and inelastically scattered to different energy states, providing an analog of the Stern--Gerlach experiment in the energy dimension. Our findings are important for optical control of free-electron spins, preparation of spin-polarized electron beams, and applications as varied as in material science and high-energy physics.
