Polaron Effect Of Quantum Wires Of Polar Crystals

The dissertation presents a systematic investigation into the polaron effect on cylindrical semiconductor quantum well quantum wire system. It is organized in three main parts.Firstly, the phonon modes and corresponding electron-phonon Frohlich interaction Hamiltonian of the cylindrical quantum wire system are derived by using the dielectric continuum approach. In a quantum well system, not only the electron is confined, so are the phonons. The corresponding phonon modes have a close relationship with the geometry of the quantum well structures. By employing the dielectric continuum model, we find that, in a free-standing cylindrical quantum wire, there exist bulk-like longitudinal optical phonon modes and surface optical phonon modes, the former is confined inside the wire and the latter is localized near the surface and is dispersive. While in a quantum well quantum wire system, there exist bulk-like longitudinal optical phonon modes both confined in the well and the barrier materials, and the interface phonon modes localized in the boundary area.Secondly, based on the phonon modes derived in the first part, we study the polaron effect in the quantum wire system. We find that the second-order pertubation theory is an effective theoretical approach to study the polaron effect in the low dimensional systems such as the quantum wires. For the convenience of analyses and comparison, in this part and here after, we limited the numerical calculation to the well-known polar semiconductor material GaAs-Ga_1xAl_x As quantum well. The polaron self energy as well as the correction to the electron effective mass are calculated under different quantum wire radii both in the free-standing quantum wire and quantum well quantum wire. Results shows that the polaron self-energy and the correction...