一维体系等离激元的偶极和四极模式的激发与调控特性

Excitation and Modulation Properties of Dipole and Quadrupole Modes of Plasmon in One-Dimensional System

利用紧束缚模型和本征方程方法,研究了一维体系中等离激元的偶极和四极模式,以及外场、体系的尺寸和电子数对这两种模式的调控作用。结果表明,外场可控制等离激元的模式,反对称的电势场仅激发偶极模式,对称电势场仅激发四极模式;利用等离激元的尺寸效应,增加一维体系的长度可减小等离激元的频率,增大激发强度;利用等离激元的电荷累积效应,在电子数达到半满之前,增大一维体系中的电子数可增大等离激元的频率和激发强度,且由于电子和空穴激发的等价性,等离激元的激发强度随电子数变化的曲线关于半满电子数对称。在等离激元的尺寸效应方面,本征方程方法得到的结果可用无规相近似方法得到较好的拟合。

By using the tight-binding model and the eigen-equation method,both the dipole and quadrupole modes of the plasmon in one-dimensional system are studied.The modulation effects of the external field,the size of system and the number of electrons on these two modes are investigated.The results show that,the modes of the plasmon can be controlled by the external field,a symmetrical electric potential field only excites the quadrupole mode,and an anti-symmetrical electric potential field only excites the dipole mode.Based on the size effect of plasmon,the increase of the length of one-dimensional system can reduce the plasmon frequency and enhance the excitation intensity.Based on the charge accumulation effect of plasmon,the increase of the number of electrons before half filling can increase the frequency and excitation intensity of plasmon.Moreover,the excitation intensity of plasmon is symmetric with respect to the half-filling electron number since the excitations of electrons and holes are equivalent.As for the size effect of plasmon,the results calculated by the eigen-equation method can be well fitted by those obtained by the random phase approximation method.