| In the frame work of effective-mass approximation, size effect and magnetic field effectof the biexciton and the negative donor center impurity system in a concentric doublequantum rings are study theoretically. Within one-dimensional concentric double quantumrings model, the ground state energy can be achieved by using exact diagonalizationtechniques. We discuss the calculation results in detail.Firstly, we research energy states of biexciton in concentric double quantum rings. Theparticles will in external ring when the inner ring radius of less than4nm; if the inner ringradius is larger than4nm, the lowest energy is achieved when biexciton is located in the innerring, and the ground state energy increases with the inner ring radius and magnetic field. Theparticles will be excited to external ring if the system is to provide an excitation energy. In thecase of zero magnetic field and weak magnetic filed, the lowest energy is achieved when oneexciton is confined within one of the rings and the other is confined in the second ring. Forthe case of a strong magnetic field, however, the lowest energy is obtained when two electronsand one hole are located in the inner ring while the second hole is located in the external ring.The excitation energy decreases with the inner ring radius and the external ring radius.Secondly, we also research energy states of the negative donor center impurity system inconcentric double quantum rings. For the case of zero magnetic field, the system changesdouble quantum ring distribution into a single quantum ring distribution as the inner ringradius increases; For the case of a magnetic field, the ground state energy in magnetic fieldcan not find A-B oscillation which be easily observed in the system of neutral donor impuritysystem center. At the same time, by adjusting the strength of the magnetic field can make thedouble quantum ring system in different distribution in certain dimensions, then it wouldconstitute a charge qubit... |
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