Excitons in a quasi-one-dimensional quantum nanorod under a strong electric field

Abstract

The response of an exciton in the ground and first excited states to a strong DC electric field is studied in a quasi-one-dimensional nano quantum well (i.e., nanorod) bounded by high symmetric barriers by studying the energy, the oscillator strength, the root-mean-square (RMS) average of the electron-hole (e-h) separation, and the average positions of the electron and the hole. The interplaying effect between the barrier confinement, e-h attraction, and the field-induced e-h separation for exciton binding is examined. We find that, for a long nanorod, the exciton energy, as well as, the oscillator strength drops abruptly as a function of the field near the exciton-dissociation field while the RMS average of the e-h separation rises rapidly. For shorter rods, the transition is more gradual due to the combined effect of the confinement and the long-range e-h interaction. A strong field is shown to transform the optically-inactive first excited state into an optically-active state in the field range between the dissociation field of the ground state and that of the first excited level. We also find that, in the ground state, the (lighter) electron is dragged by the (heavier) hole below the dissociation field. The dependence of the above mentioned properties on the rod length is also investigated for varying fields. The results are compared with those obtained for the rods with parabolic confinement.