Spin-orbit interaction in thin bismuth films

Abstract

The magnetic-field dependences of the resistance of thin (100–700 Å thick) bismuth films at low temperatures are analyzed using quantum corrections to the conductivity with weak electron localization. It is shown that the spin-orbit scattering time τso is much shorter than the phase relaxation time τφ of the electrons (the case of a strong spin-orbit interaction). It is found that τso tends to increase with the film thickness. This shows that the surface scattering of the electrons plays a dominant role in spin-orbit processes. Apparently, strong spin relaxation in the presence of surface scattering is due to the gradient of the internal crystal-field potential near the surface of the metal, resulting in lifting of the spin degeneracy and in the appearance of a spin gap (Rashba mechanism).