Spin splitting of surface states in HgTe quantum wells

TL;DR

This paper investigates the large Rashba-like spin splitting in HgTe quantum wells, revealing two electron concentrations at the Fermi level due to surface state hybridization, supported by experimental and theoretical analysis.

Contribution

It provides a detailed analysis of spin splitting in HgTe quantum wells, combining experimental data with self-consistent calculations to elucidate the surface state origin of the effect.

Findings

Observation of beating in Shubnikov-de Haas oscillations indicating spin splitting.

Quantitative agreement between experimental data and theoretical models.

Identification of surface states as the cause of large spin splitting.

Abstract

We report on beating appearance in Shubnikov-de Haas oscillations in conduction band of 18-22nm 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 dN_s 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 dN_s are also in a good quantitative agreement with self-consistent calculations of Poisson and Schrodinger equations with eight-band kp 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.