Anomalous shift of the beating nodes in illumination-controlledIn1−xGaxAs/In1−yAlyAstwo-dimensional electron gases with strong spin-orbit interaction

Abstract

The beating patterns in the Shubnikov-de Haas oscillatory magnetoresistance originating from zero-field spin splitting of two-dimensional electron gases (2DEGs) in ${\text{In}}_{0.52}{\text{Al}}_{0.48}\text{As}/{\text{In}}_{\text{x}}{\text{Ga}}_{1\ensuremath{-}\text{x}}\text{As}/{\text{In}}_{0.52}{\text{Al}}_{0.48}\text{As}$ quantum wells with silicon $\ensuremath{\delta}$ doped on the upper barrier layer have been investigated by means of magnetotransport measurements before and after illumination. Contrary to the expectation, after each illumination, the beating nodes induced by the zero-field spin-splitting effect shift to lower and lower magnetic field due to the decrease in the zero-field spin-splitting energy of the 2DEGs. The anomalous phenomenon of the shift of the beating nodes and the decrease in spin-orbit coupling constants after illumination cannot be explained by utilizing the previous linear Rashba model. It is suggested that the decrease in the zero-field spin-splitting energy and the spin-orbit coupling constant arise from the nonlinear Rashba spin splitting.