Electronic States And Transport Properties Of Quantum Rings In Magnetic Fields

In recent years, with the development of low- dimensional semiconductor devices fabrication technology, quantum rings have attracted considerable interest because of its unique physical properties and potential applications.In former theories of quantum rings, eccentric circular parabolic potential model is widely used. The parabolic confined potentials are successively employed to calculate the problems of quantum dots. However, for quantum rings, we do not think that the parabolic confined potential is a good approximation. So we study the electronic states of two-dimensional quantum dots and rings with a finite high cylindrical square-well potential in perpendicular magnetic field and transport properties of corresponding AB rings, and the wave function is expanded in terms of the two-dimensional isotropic harmonic oscillator.In this thesis, the factor of the perpendicular magnetic fields influence on the quantum level is studied. The results show that when the magnetic field strength is fixed, if the radius of the quantum dot reduces, the impact of potential barrier on its energy level will increase; when the radius of quantum dot is settled, with the magnetic field strength increases, the impact of the potential barrier on its energy level will increase. At the same magnetic field strength, the energy minimum of quantum ring is at m <0 state, which is caused by the m linear term in Landau level, and the absolute value of m at which the energy minimum is located also very dependent on the magnetic field and quantum ring inner radius R1; When the magnetic field increases the ground state changes gradually from an m =0 state to m =?1, ? 2,…states. And we draw a conclusion that the real confinement potential width we received from our model is larger than that received by infinite hard-wall approximation, but the electronic energy level is lower.Then we use transfer matrix method to study the transport properties of AB ring. It is found that tunneling probability T shows very typical resonant tunneling property. The energy values of resonance peaks correspond to the values of confined energy k of the closed ring, and with the magnetic field increases, resonance peaks will reduce.