Gate control of Rashba spin-orbit coupling in multiple-quantum-well structure: From one to multiple subbands

Abstract

We present in multiple-quantum-well structure a full dynamic picture of Rashba spin-orbit coupling (SOC) with continuous variation from one- to multi-subband occupation, mediated by the external gate potential. Some novel features of Rashba effect can be demonstrated. For intrasubband SOC ανs (ν=1,2,3...is subband index), they show distinct gate dependences which facilitates selective control of ανs with the help of the gate. Specifically, α1 of the lowest subband is always the largest under negative gate potentials, which leads to large spin splitting, desirable for spin detection, while ανs of the highest subband is immune to the gate and keeps zero in a wide gate range, making it possible to suppress electron spin relaxation of these subbands regardless of the gate variation. For intersubband SOC, it is impressive to discover that the intersubband coupling between two nonadjacent subbands with relatively large energy separation can exceed that between two adjacent subbands and dominates the intersubband coupling. Our results should provide new insights for spintronic application based on intra- and intersubband spin-orbit effects, such as spin blocker, topological superconductivity, and all-electron topological insulator.