Abstract
AbstractStructure inversion asymmetry is an inherent feature of quantum confined heterostructures with non‐equivalent interfaces. It leads to a spin splitting of the electron states and strongly affects the electronic band structure. The effect is particularly large in topological insulators because the topological surface states are extremely sensitive to the interfaces. Here, the first experimental observation and theoretical explication of this effect are reported for topological crystalline insulator quantum wells made of Pb1−xSnxSe confined by Pb1−yEuySe barriers on one side and by vacuum on the other. This provides a well defined structure asymmetry controlled by the surface condition. The electronic structure is mapped out by angle‐resolved photoemission spectroscopy and tight binding calculations, evidencing that the spin splitting decisively depends on hybridization and, thus, quantum well width. Most importantly, the topological boundary states are not only split in energy but also separated in space—unlike conventional Rashba bands that are splitted only in momentum. The splitting can be strongly enhanced to very large values by control of the surface termination due to the charge imbalance at the polar quantum well surface. The findings thus, open up a wide parameter space for tuning of such systems for device applications.
Highlights
Structure inversion asymmetry is an inherent feature of quantum confined applications.[1,2,3,4] Due to their non-trivial topology of electronic band structure, heterostructures with non-equivalent interfaces
To assess the effect of structure inversion asymmetry (SIA) on the electronic quantum wells (QWs) states, we start with the generic asymmetry of the heterostructures arising from the different boundary conditions and confining barriers, defined by the connection to vacuum at the top surface and to the Pb1−yEuySe barrier on the bottom interface
The pronounced effect of the different boundary conditions is demonstrated by Figure 4, where we compare the spectral function at the QW surface for freestanding, that is, symmetric Pb1−xSnxSe slabs with identical termination on both sides, with those of asymmetric Pb1−xSnxSe/ Pb1−yEuySe heterostructures with anion termination on the vacuum and a solid state interface on the bottom side
Summary
Structure inversion asymmetry is an inherent feature of quantum confined applications.[1,2,3,4] Due to their non-trivial topology of electronic band structure, heterostructures with non-equivalent interfaces. The first experimental observation and theoretical explication of this effect are reported for emerge at the surface whose wave functions decay exponentially into the bulk In these states, the electron spin is locked to the momentum and the energy spectrum is described by Dirac cones connecting the topological crystalline insulator quantum wells made of Pb1−xSnxSe confined valence with the conduction band.[1,2,3] In by Pb1−yEuySe barriers on one side and by vacuum on the other. The electron spin is locked to the momentum and the energy spectrum is described by Dirac cones connecting the topological crystalline insulator quantum wells made of Pb1−xSnxSe confined valence with the conduction band.[1,2,3] In by Pb1−yEuySe barriers on one side and by vacuum on the other This provides a well defined structure asymmetry controlled by the surface condition.
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