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# Research on Dielectric Function of Dielectric Medium and Metal

Author: FengHongXu
Tutor: DuAn
School: Northeastern University
Course: Theoretical Physics
Keywords: dielectric function electric dipole polarization harmonic vibration of bindingelectron plasma oscillation resonance
CLC: O484.4
Type: Master's thesis
Year: 2011
Quote: 0

### Abstract

 Recently, the development of electromagnetic wave and material is faster and faster, which brings us into information period. The convenient and fast information transmitting makes people feel like living in the earth village. Nano materials have many strange properties because of their tiny sizes. People find they have much better properties than common materials, which makes nano materials gain much favor from a lot of scientists of all subjects. This essay is to analyze the dielectric function of dielectric medium and metal at the view of microcosmic point.Firstly, we discuss the dielectric function of dielectric medium. In accordance with physics truth, an electric dipole model is set up in the field of electric field and anisotropy field, and then we can write out its second-order kinetic differential equation, which can be worked out by the means of numerical analysis in the method of Runge-Kutta using Fortran programmer language. By analyzing the diagram of θ-t, we can know that the movement of this electric dipole is periodic swing. By increasing the frequency of external electric field, we can see that the period of θ is decreasing and its maximum is increasing, which has less time and process to reach. Then in accordance with dielectric theory, we can get the relationship of dielectric function and intensity of polarization. Using Fourier transform, we can gain the diagram of the dielectric function and the frequency of external electric field, so as to analyze the response characteristics of an electric dipole effecting on electromagnetic waves at the view of microcosmic point intuitively. Then we talk about the effect of some physical quantities to dielectric function. The initial value of6has effect on the shape of the real part of dielectric function. The initial value of ω has effect on the value range of the imaginary part of dielectric function. The amplitudes of anisotropic and adscititious electric field have effect on the value range of the real part of dielectric function and both the shape and value range of the imaginary part of dielectric function. To study the dielectric function of metal, we can set up harmonic vibration model of binding electron and free electrons of metal films on the base of electron displacement polarization, so as to gain kinetic equations of binding electron and free electron. In accordance with them, we can deduce relationship between dielectric function of metal film and frequency of electromagnetic waves. Then we can draw their curves, from which we can see the real part of metal dielectric function is a constant at low frequency field, while when it comes to the resonance frequency, the curve will have two pairs of rise and fall peaks and in the end, the metal dielectric function will be near the constant of one at high frequency field. Especially for nano-magnetic films, we can see that the curve has two main pairs of absorption and reflection peaks, the biggest and lowest peak values are both as large as we can imagine. As for the imaginary part of metal dielectric function, we can see that its value is near zero both in the field of the high and low frequencies and at the resonance frequency, there will be absorption peaks.

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