Spin splitting of surface states in HgTe quantum wells

We report on beating appearance in Shubnikov-de Haas oscillations in conduction band of 18–22 nm HgTe quantum wells under applied top-gate voltage. Analysis of the beatings reveals two electron concentrations at the Fermi level arising due to Rashba-like spin splitting of the first conduction subband H1. The difference ΔNs in two concentrations as a function of the gate voltage is qualitatively explained by a proposed toy electrostatic model involving the surface states localized at quantum well interfaces. Experimental values of ΔNs are also in a good quantitative agreement with self-consistent calculations of Poisson and Schrodinger equations with eight- band k ⋅ p Hamiltonian. Our results clearly demonstrate that the large spin splitting of the first conduction subband is caused by surface nature of H1 states hybridized with the heavy-hole band.We report on beating appearance in Shubnikov-de Haas oscillations in conduction band of 18–22 nm HgTe quantum wells under applied top-gate voltage. Analysis of the beatings reveals two electron concentrations at the Fermi level arising due to Rashba-like spin splitting of the first conduction subband H1. The difference ΔNs in two concentrations as a function of the gate voltage is qualitatively explained by a proposed toy electrostatic model involving the surface states localized at quantum well interfaces. Experimental values of ΔNs are also in a good quantitative agreement with self-consistent calculations of Poisson and Schrodinger equations with eight- band k ⋅ p Hamiltonian. Our results clearly demonstrate that the large spin splitting of the first conduction subband is caused by surface nature of H1 states hybridized with the heavy-hole band.