By recasting the definition of the dielectric constants in terms of currents, as well as using atomistic simulations and analytical derivations, we show that the dielectric permittivity can be negative at an ultrashort timescale, under perfect screening conditions and for very different materials and switching mechanisms, in line with recent experiments and modelings. In particular, we found that this effect can be due to a previously overlooked phenomenon of postswitching polarization oscillations. We also derived practical analytical formulas that can be experimentally checked.

中文翻译：

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超短固有负介电常数的普遍性和起源

通过用电流重铸介电常数的定义，以及使用原子模拟和分析推导，我们表明，在完美的屏蔽条件下，对于非常不同的材料和开关机制，介电常数在超短时间范围内可能为负，符合最近的实验和建模。特别是，我们发现这种影响可能是由于先前被忽视的开关后极化振荡现象引起的。我们还导出了可以通过实验检查的实用分析公式。