Interplay between resonant tunneling and spin precession oscillations in all-electric all-semiconductor spin transistors

We investigate the transmission properties of a spin transistor coupled to two quantum point contacts acting as spin injector and detector. In the Fabry-Perot regime, transport is mediated by quasibound states formed between tunnel barriers. Interestingly, the spin-orbit interaction of the Rashba type can be tuned in such a way that nonuniform Rashba fields can point along distinct directions in different points of the sample. We discuss both spin-conserving and spin-flipping transitions as the spin-orbit angle of orientation increases from parallel to antiparallel configurations. Spin precession oscillations are clearly seen as a function of the length of the central channel. Remarkably, we find that these oscillations combine with the Fabry-Perot motion giving rise to quasiperiodic transmissions in the purely one-dimensional case. Furthermore, we consider the more realistic case of a finite width in the transverse direction and find that the coherent oscillations become deteriorated for moderate values of the spin-orbit strength. Our results then determine the precise role of the Rashba intersubband coupling potential in the Fabry-Perot-Datta-Das intermixed oscillations.