相干平行板电容器对外场的动态响应

Dynamic response of the coherent parallel-plate capacitor to the external field

基于介观体系动态响应的自洽理论,讨论了介观相干平行板电容器的电容.结果表明相干电容器的电容对外场频率有很强的依赖关系,并且是随频率变化的复变函数.该电容随频率的变化关系呈现出一个非常有意义的特性,即电容虚部曲线有一个较尖锐的峰,它正好与电容实部的极小位置相对应,而进一步研究发现它们与该电容体系中的类等离子体激发相联系.另外,也讨论了介观电容的尺寸效应,发现当极板间距很大时,电容值和宏观的几何电容结果趋于一致.

We discuss the capacitance of a coherent mesoscopic parallel-plate capacitor based on the self-consistent theory of dynamic response for mesoscopic systems. The results show that the capacitance is a complex function of frequency which is strongly dependent on the frequency of the external field. The capacitance-frequency curve shows a significant characteristic that a peak in the imaginary part of the capacitance corresponds to the minimum in the real part, and further study shows that they are related to a plasmon-like excitation. In addition,we discuss the size effect of the capacitor, and find that the capacitance approaches geometric capacitance when the distance between two plates of the capacitor is very large.