Abstract
We present an analytical investigation of quasi-one-dimensional excitons in thin uniform (single) and double nanoscaled cylindrical quantum wires (UQWR and DQWR) surrounded by a barrier of infinite height and exposed to external electric and strong magnetic fields. The DQWR is formed by inserting an impenetrable longitudinal barrier in a single-quantum wire. Both external fields are directed parallel to the quantum wire (QWR) axis. The radius of the QWRs and the magnetic length are taken to be much less than the exciton Bohr radius. For the dependencies of the positions and widths of the complex quasidiscrete energy levels of the indirect exciton in the DQWR, in which the carriers are separated by the insertion on the confinement, electric field strength and width of the interwire barrier are derived. The confinement (insertion) leads to an increase (decrease) of the exciton binding energy. The impact of the electric field ionization of the exciton is less pronounced for strongly confined and weakly separated carriers. The coefficient of the exciton absorption in the UQWR as a function of the confinement and electric field is calculated in an explicit form. The effect of the confinement and electric field on the exciton peak closely resembles that on the quasidiscrete level of the indirect exciton in the DQWR. Electron-hole attraction increases remarkably the optical Franz-Keldysh electroabsorption in the frequency region below the edge and distant from the exciton peaks. The coefficient of absorption reflecting the electric field ionization and autoionization caused by the coupling between the discrete and continuous exciton states adjacent to the different size-quantized or Landau levels is obtained analytically. A comparison of our analytical results with numerical data is performed. Estimates of the expected experimental values for the parameters of GaAs/GaAlAs QWR show that the autoionized exciton magnetostates in thin biased QWRs are sufficiently stable to be observed.
2 More- Received 16 July 2008
DOI:https://doi.org/10.1103/PhysRevB.79.165314
©2009 American Physical Society