Semiconductor quantum tubes: Dielectric modulation and excitonic response

We study theoretically the optical properties of quantum tubes, one-dimensional semiconductor nanostructureswhere electrons and holes are confined to a cylindrical shell. In these structures, which bridge betweentwo-dimensional and one-dimensional systems, the electron-hole interaction may be modulated by a dielectricsubstance outside the quantum tube and possibly inside its core. We use the exact Green’s function for theappropriate dielectric configuration and exact diagonalization of the electron-hole interaction within aneffective-mass description to predict the evolution of the exciton binding energy and oscillator strength.Contrary to the homogeneous case, in dielectrically modulated tubes, the exciton binding is a function of thetube diameter and can be tuned to a large extent by structure design and proper choice of the dielectric media.