Studies On Plasmon Characteristics In Semiconductor Symmetric Double Quantum Wells

Due to its importance in revealing the electron-electron interaction mechanisms, properties of collective excitation in low-dimensional semiconductor structures such as superlattices, quantum wells, quantum wires, and quantum dots have become one of the frontier research fields in condensed matter physics and received durable attention now. In recent years, the research on collective excitation in low-dimensional semiconductor system mostly focused on the match dielectric systems. In this thesis, we investigated the influence of the image potential which was caused by dielectric mismatch on the features of the plasmon modes in semiconductor symmetric double quantum wells. And we compared the differences between the results obtained in the cases of dielectric match and mismatch of materials.In single-particle Hamilton eigenvector space, we derived dielectric function of semiconductor symmetric double quantum wells based on random-phase approximation (RPA) framework. In the two-subband model, we got some formulas which can determine the intrasubband and intersubband plasmon modes. We adopt image potential method to calculate the positions and value of the image charge, and obtained the formula of interaction potential which contained image potentials.We calculated two collective excitation spectrums both dielectric match and mismatch material systems, the higher branch represented the intersubband collective excitation, while the lower branch represented the intrasubband collective excitation. The two branches were independent each other. Compared with the case of dielectric match, as a result of the image potential effects, both the intrasubband and intersubband plasmon modes had been changed. The change of intersubband plasmon modes was notable with the increase of q, as the q was larger than a critical value, the intersubband collective excitations decayed into single-particle excitation region.