The inner barrier mediated spin–orbit control in stepped quantum wells

Abstract

The inner barrier in stepped quantum wells, which embrace an intrinsic structural inversion asymmetry (SIA), offers more possibilities for the multi-band spin–orbit (SO) control. By varying the inner band offset [Formula: see text], which adjusts the quantum confinement for electrons and also the SIA, we reveal that both the Rashba ([Formula: see text]) and Dresselhaus ([Formula: see text]) SO coeffcients of the two subbands exhibit contrasting dependence on [Formula: see text]. Also, [Formula: see text] and [Formula: see text] may have opposite signs, depending on the value of [Formula: see text]. By fine tuning the inner offset, there may even exist a scenario in which [Formula: see text] identically vanishes but [Formula: see text] is finite, offering a knob on how to subband-selectively suppress spin relaxation induced by SO coupling. In addition, by resorting to an external gate [Formula: see text], we reveal that in the regime of [Formula: see text] and [Formula: see text] having opposite signs, their magnitudes also vary with [Formula: see text] in an opposite manner. This, together with the engineered inner barrier of stepped wells, will facilitate flexible spin manipulation. Finally, the interband SO couplings, which depend on the spatial overlap of wave functions of distinct subbands and the corresponding parities, are also discussed.