Schwinger对产生和Dirac材料中无子周期的谱条纹
Spectral fringes without subcycles in Schwinger pair production and Dirac materials
AI总结：
该研究展示了在Schwinger对产生和Dirac材料中，即使在没有子周期的光滑单峰电场脉冲下，也能出现明显的谱条纹，通过比较高斯脉冲和弱变形脉冲在非绝热过渡中的纵向动量谱差异，揭示了谱条纹的形成机制。
摘要：
Schwinger对产生中的谱条纹通常归因于结构化的驱动，如载流子振荡、脉冲序列或多个产生事件。我们证明，即使在光滑、无载流子的单峰电场脉冲下，也能出现明显的条纹。两种在现实时间中几乎无法区分的钟形轮廓——高斯脉冲和弱变形变体——在非绝热过渡中产生定性不同的纵向动量谱：高斯谱保持平滑，而变形脉冲在Keldysh参数接近单位时发展出强条纹。标量和旋量QED的精确数值解与半经典转折点分析一致，并追溯到转折点主导过渡，其中主导的鞍点变得无关，而次主导贡献发生干涉。我们在固态Schwinger类比中展示了相同机制，该类比由相关于SiC上的外延石墨烯的带隙二维Dirac模型描述，并讨论了通过能量分辨的泵浦-探测方法来观测预测调制的途径。
英文摘要：
Spectral fringes in Schwinger pair creation are usually attributed to structured driving, such as carrier oscillations, pulse trains, or multiple creation events. We show that pronounced fringes can arise even for smooth, carrier-free single-lobe electric-field pulses. Two bell-shaped profiles that are nearly indistinguishable in real time - a Gaussian pulse and a weakly deformed variant - produce qualitatively different longitudinal momentum spectra in the nonadiabatic crossover: the Gaussian spectrum remains smooth, whereas the deformed pulse develops strong fringes as the Keldysh parameter approaches unity. Exact numerical solutions in scalar and spinor QED agree with a semiclassical turning-point analysis and trace the effect to a turning-point dominance transition, where the leading saddle becomes irrelevant and subleading contributions interfere. We demonstrate the same mechanism in a solid-state Schwinger analog described by a gapped two-dimensional Dirac model relevant to epitaxial graphene on SiC, and discuss an energy-resolved pump-probe route to observing the predicted modulation.
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