Effect of magnetic field on off-axis donor binding energy in a nanotube

We analyze the effect of the mixing of the low‐lying s and px ,y subbands on the ground‐state binding energy of the off‐axis donors in cylindrical nanotubes in the presence of a magnetic field parallel to the axis. We express the wave function as a product of combinations of s and p subband wave functions and an envelope function that depends only on the electron–ion separation. By using the variational principle we derive a differential equation for the envelope function, which we solve numerically. The curves for the dependence of the ground‐state binding energies on the donor distance from the axis are presented and it is shown that the effect of the subband mixing for off‐axis donors in nanotubes is considerable. It is found that the magnetic field enhances the binding energies of donors located close to the axis whereas for donors located far from the axis the effect of the magnetic field on the binding energy is the opposite. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)