Spin-orbit splitting of the conduction band in HgTe quantum wells: Role of different mechanisms

Abstract

Spin-orbit splitting of conduction band in HgTe quantum wells was studied experimentally. In order to recognize the role of different mechanisms, we carried out detailed measurements of the Shubnikov-de Haas oscillations in gated structures with a quantum well widths from 8 to 18 nm over a wide range of electron density. With increasing electron density controlled by the gate voltage, splitting of the maximum of the oscillation Fourier spectrum f 0 into two components f 1 and f 2 and the appearance of the low-frequency component f 3 was observed. Our analysis shows that the components f 1 and f 2 are determined by the electron densities n 1 and n 2 in spin-orbit split subbands while the f 3 component results from magneto-intersubband oscillations so that it is determined by the difference between these densities Δn. This allows us to obtain all three values n 1 , n 2 and Δn independently. Comparison of the data obtained with results of self-consistent calculations carried out within the framework of four-band kP model shows that the main contribution to spin-orbit splitting comes from the Bychkov-Rashba effect. Contribution of the interface inversion asymmetry to the splitting of the conduction band turns out to be four-to-five times less than that for the valence band in the same structures. © 2019 Elsevier B.V.