发表机构
MNIT Jaipur（马拉维亚国家理工学院斋浦尔分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过量子动力学方法计算旋转电场下电子-正电子对产生的螺旋性分辨动量分布，发现频率啁啾可显著增强螺旋性不对称，弱场啁啾效果最佳，为自旋动力学提供新信息。
AI 中文摘要
我们利用费米子的量子动力学形式，研究了在具有频率啁啾的圆偏振电场中电子-正电子对产生过程中的螺旋性效应。特别地，我们计算了螺旋性分辨的动量分布，并通过螺旋性不对称参数表征了各种电场构型下的螺旋性不平衡，这些构型包括时间不对称场以及具有不同频率啁啾配置的动态辅助双色场。我们发现，右螺旋性和左螺旋性电子优先占据沿面外动量方向相反的动量半空间，导致产生的电子分布中出现显著的螺旋性不对称。对于时间不对称场，频率啁啾显著改变动量分布，并能强烈增强螺旋性不对称，其响应敏感地依赖于脉冲不对称参数。对于对称和拉长脉冲，在足够大的啁啾强度下，螺旋性不对称接近100%，而压缩脉冲情况则表现出定性不同的响应，在大啁啾下不对称性被抑制。对于动态辅助场，对弱高频分量进行啁啾产生最强的螺旋性响应，在组合场中达到近87%的最大不对称性，而仅对强场进行啁啾仅产生约12%-14%的适度不对称性。同时啁啾产生大的螺旋性不平衡以及动量谱的显著重构，尽管其螺旋性响应弱于单独对弱场啁啾所获得的结果。这些结果表明，螺旋性分辨的动量分布提供了超越螺旋性求和谱所包含的关于Schwinger对产生自旋依赖动力学的额外信息。
英文摘要
We investigate helicity effects in electron-positron pair production in circularly polarized electric fields with frequency chirping using the quantum-kinetic formalism for fermions. In particular, we calculate helicity-resolved momentum distributions and characterize the helicity imbalance through the helicity-asymmetry parameter for various electric-field configurations, including temporally asymmetric fields and dynamically assisted two-color fields with different frequency-chirping configurations. We find that right- and left-helicity electrons preferentially populate opposite momentum half-spaces along the out-of-plane momentum direction, leading to a pronounced helicity asymmetry in the produced electron distributions. For temporally asymmetric fields, frequency chirping substantially modifies the momentum distributions and can strongly enhance the helicity asymmetry, with the response depending sensitively on the pulse asymmetry parameter. For symmetric and elongated pulses, the helicity asymmetry approaches 100% at sufficiently large chirp strengths, whereas the compressed-pulse case exhibits a qualitatively different response with suppressed asymmetry at large chirp. For dynamically assisted fields, chirping the weak high-frequency component produces the strongest helicity response, reaching a maximum asymmetry of nearly 87% in the combined field, while chirping the strong field alone results in only a moderate asymmetry of about 12%-14%. Simultaneous chirping produces a large helicity imbalance together with substantial restructuring of the momentum spectrum, although its helicity response is weaker than that obtained by chirping the weak field alone. These results demonstrate that helicity-resolved momentum distributions provide additional information on the spin-dependent dynamics of Schwinger pair production beyond that contained in helicity-summed spectra.
Comments18 pages, 10 figures
