库仑场对抛物量子点中强耦合极化子性质的影响

Influence of the Coulomb Field on the Properties of Strong-coupling Bound Polaron in Parabolic Quantum Dot

采用线性组合算符和幺正变换方法研究了在库仑场束缚下抛物量子点中强耦合束缚极化子的振动频率和基态能量。并对其进行了数值计算,结果表明:强耦合束缚极化子的振动频率和基态能量随量子点的有效受限长度的增加而减小,随电子-LO声子耦合强度的增加而增加,束缚极化子的基态能量随库仑势的增加而减小。

With the development of semiconductor growth technology, people have produced kinds of quantum dots. Due to the novel optoelectronic properties and the transport characteristics of quantum dots, there will be a widely applied prospect for them. Many investigators studied the properties of a quantum dot by means of various theoretical and experimental methods. In recent years, with the study of the properties of bound polaron in a quantum dot, people have paid more attention to them. Woggon et al. studied the states of polarons bound in a potential and determined the local optical absorption spectrum up to first-order time-dependent perturbation theory with respect to the electron-phonon interaction. Chen et al. derived the expression of the ground state energy, of an electron coupled simultaneously with a coulomb potential and a longitudinal-optical phonon field in parabolic quantum dots and wires within the framework of Feynman variational path-integral theory. Xie et al. investigated the binding energy of a bound polaron in a spherical quantum dot by using the variational method, and so on. However, few investigators studied the bound polaron in the quantum dot with the linear combination operator method so far. By using the linear combination operator and unitary transformation method, the properties of the bound polaron in a parabolic quantum dot are studied for the strong electron-phonon coupling case. Results show that the vibration frequency of the strong-coupling bound polaron in a parabolic quantum dot will increase strongly with decreasing the effective confinement length of quantum dot and increase with increasing the electron phonon coupling strength. The ground state energy of the strong-coupling bound polaron will increase strongly with decreasing the effective confinement length, and at the same value of the confinement length, the higher the coupling strength, the higher is the value of the ground state energy. The ground state energy of strong-coupling bound polaron change little with electron-phonon coupling strength for l0 〉 0. 30, whereas they change strongly with electron-phonon coupling strength for l0 〉 0.30. The ground state energy of strong-coupling bound polaron will increase with increasing, the coulomb bound potential. From the equation of the effective confinement length of the quantum dot l0√h/mω0 we can see that the effective confinement length of quantum dot is reciprocal with the square root of the confinement strength ω0 of the quantum dot. Thus the vibration frequency and the ground state energy of strong-coupling bound polaron in a parabolic quantum dot will increase with increasing the confinement strength.