Wave function control in single semiconductor quantum dots with a magnetic field

Abstract

Normally, wave functions in single quantum dots can be tuned transversely by a perpendicular magnetic field because of the cyclotron energy. In this work, we are presenting a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field, the hole wave function shrinks in the base plane, resulting in that the center of effective mass moves towards apex. For electrons, however, the center of effective mass does not move much. This induces a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots. Additionally, the many-body exciton states in a coupled system with a single self-assembled quantum dot and a wetting layer are observed by strong anomalous diamagnetic shifts. A tremendous positive diamagnetic coefficient is observed when an electron in the wetting layer combines with a hole in quantum dot, which is nearly one order of magnitude larger than that of the excitonic states confined in quantum dots. When the electrons recombine with holes within quantum dot in the coupled system, a peculiar negative diamagnetic effect is observed. The properties of emitted photons depending on the large electron wave function extents in wetting layer indicate the coupling between the systems in different dimensionality, which was also verified by a magnetic field applied in different configurations.