Spin properties of silicon-germanium nanotubes

The dependence of the electronic structure on the chirality of single-walled SiGe nanotubes has been studied using the quantum chemistry methods. It has been shown that all nanotubes have a semiconductor type of band structure with a band gap Eg of about 0.35 eV, which distinguishes them from silicon analogues, which, depending on chirality, have semiconductor, semimetallic or metallic properties. This difference is due to the polarity of the Si-Ge chemical bond and, as a consequence, the influence of the antisymmetric component of the electronic potential on the band structure of the compounds. The valence band with a width of about 12 eV includes an inner band of predominantly s electrons of atoms with a width of 2 eV and a band of p electrons located above with a width of 8 eV. The energies of the spin-orbit gaps of the edges of the valence band and the conduction band differ significantly: for non-chiral nanotubes, they are equal to several tenths, and for chiral nanotubes, they are several meV. Using mechanical action, for example, by twisting a nanotube around its axis, it is possible to control the energies of spin-orbit gaps, which can find application in spintronics.