Research On Energy States And Optical Properties Of Two Electrons And Excitons In Quantum Rings In A Magnetic Field

In recent years, quantum rings of the low-dimensional semiconductor system have attracted much attention because of their unique physical property and wide prospect of application. Accordingly, much work (experimental and theoretical) has also been done in this field.Among many theoretical models, the eccentric circular parabolic potential (ECPP) model is widely adopted for the study of quantum rings. However, ECPP model has difficulty in describing the effect of quantum ring's inner and outer radius on electronic states in a quantum ring and adjusting the parameter of center-potential-barrier height of the quantum ring. Afterward, the fine circular potential model is put forward, but carrying through theoretical analysis of quantum rings under this model is inconvenient because it has too many parameters. Thus we adopt the finite eccentric circular parabolic potential (FECPP) model put forward by Yong-Li Xing et al. This model not only can avoid difficulties in applying the two models above but also can reasonably describe the ringlike confinement potential of the quantum ring. Under this model, using the exact diagonalization method, we study energy states and optical properties of two electrons and excitons in a InGaAs quantum ring in a magnetic field.Firstly, we research electronic states and FIR spectroscopy of two electrons in quantum rings in a magnetic field. With the increase of magnetic field the ground state presents oscillation between the singlet and triplet state. And FIR absorption resonance energies have a fair agreement with experimental results. Consequently, this model is suitable to describe the physical property of electronic states and FIR spectroscopy of two electrons in quantum rings.Secondly, we also research binding energies and PL spectroscopy of excitons in quantum rings in a magnetic field. According to the FECPP model we calculate emission peak energies of excitons as a function of magnetic field, and the results agree with experimental ones. Moreover, in a high magnetic field and a high-energy level our results are much closer to experimental ones than under the FECPP model. Besides, we obtain ascription of the energy levels corresponding to experimental results signed by"cross"modes that was not obtained under ECPP model. It demonstrates that the FECPP model is also suitable to describe the physical property of binding energies and PL spectroscopy of excitons in quantum rings.Compared with the ECPP model, the FECPP model not only can give an appropriate width and center-potential-barrier height of potential and can describe the ringlike confinement potential of the quantum ring reasonably but also can describe the practical fabrication course of a quantum ring. Furthermore, this model is more suitable for researching the problems with a high magnetic field and a high-energy level.