We study theoretically the optical properties of quantum tubes,
one-dimensional semiconductor nanostructures where electrons and holes are
confined to a cylindrical shell. In these structures, which bridge between 2D
and 1D systems, the electron-hole interaction may be modulated by a dielectric
substance outside the quantum tube and possibly inside its core. We use the
exact Green's function for the appropriate dielectric configuration and exact
diagonalization of the electron-hole interaction within an effective 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 the tube diameter and can
be tuned to a large extent by structure design and proper choice of the
dielectric media.Comment: 9 pages, 6 figures, in print for Phys. Rev.
