Electron-hole symmetry and spin-orbit splitting in IV-VI asymmetric quantum wells

It is shown that, due to the electron-hole symmetry of the fundamental gap of the lead-salts (PbTe, PbSe and PbS), the Rashba spin splitting in their flat band asymmetric quantum wells is much reduced with the usual equal conduction and valence band-offsets. Different from the III-V case, we find that the important structure inversion asymmetry for the Rashba splitting in IV-VI quantum wells with different left and right barriers is not a material property (i.e., barrier height, effective mass or band gap) but results from the band alignment. This is shown by specific envelope function calculations of the spin-dependent subband structure of Pb1-xEuxTe/PbTe/Pb1-yEuyTe asymmetric quantum wells (x not equal y), based on a simple but accurate four-band kp model for the bulk band structure near the gap, which takes into account band anisotropy, nonparabolicity and multi-valley effects. (C) 2003 Published by Elsevier B.V.