Spin splitting in asymmetric double quantum wells: a mechanism for spin-dependent hole delocalization

We show how the breakdown of Kramers degeneracy for spin-orbit coupled bands in asymmetric double quantum wells may give rise to a new mechanism for tunneling which does not require resonant conditions. The most interesting aspect of this finding is that, in this case, there is a ‘‘spin’’-dependent delocalization of the wave function, leading to preferential tunneling of one ‘‘spin’’ state. We relate this effect to the symmetry properties of the wave functions of both single and asymmetric double quantum wells, and provide a qualitative explanation in terms of perturbation theory.