Unprotected edge modes in quantum spin Hall insulator candidate materials

Abstract

The experiments in quantum spin Hall insulator candidate materials, such as HgTe/CdTe and InAs/GaSb heterostructures, indicate that in addition to the topologically protected helical edge modes these multilayer heterostructures may also support additional edge states, which can contribute to the scattering and the transport. We use first-principles calculations to derive an effective tight-binding model for HgTe/CdTe, HgS/CdTe and InAs/GaSb heterostructures, and we show that all these materials support additional edge states which are sensitive to the edge termination. We trace the microscopic origin of these states back to a minimal model supporting flat bands with a nontrivial quantum geometry that gives rise to polarization charges at the edges. We show that the polarization charges transform into the additional edge states when the flat bands are coupled to each other and to the other states to form the Hamiltonian describing the full heterostructure. Interestingly, in the HgTe/CdTe quantum wells the additional edge states are far away from the Fermi level so that they do not contribute to the transport but in the HgS/CdTe and InAs/GaSb heterostructures they appear within the bulk energy gap giving rise to the possibility of multimode edge transport. Finally, we demonstrate that because these additional edge modes are non-topological it is possible to remove them from the bulk energy gap by modifying the edge potential for example with the help of a side gate or chemical doping.

arXiv comment11 pages, 9 figures

References in corpus (28)

• Topological Insulators
• Topological insulators and superconductors
• Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells
• Quantum Spin Hall Insulator State in HgTe Quantum Wells
• Maximally-localized generalized Wannier functions for composite energy bands
• Wannier90: A Tool for Obtaining Maximally-Localised Wannier Functions
• Maximally-localized Wannier functions for entangled energy bands
• Non-Bloch Band Theory of Non-Hermitian Systems
• Observation of the Quantum Spin Hall Effect up to 100 Kelvin in a Monolayer Crystal
• Quantum Spin Hall Effect in Inverted Type II Semiconductors
• Observation of Quantum Spin Hall States in InAs/GaSb Bilayers under Broken Time-Reversal Symmetry
• Performance of the modified Becke-Johnson potential
• Bulk-boundary correspondence from the inter-cellular Zak phase
• Conductance of a helical edge liquid coupled to a magnetic impurity
• Phonon induced backscattering in helical edge states
• Resistance of helical edges formed in a semiconductor heterostructure
• Edge Transport in the Trivial Phase of InAs/GaSb
• Interplay of exciton condensation and quantum spin Hall effect in InAs/GaSb bilayers
• Aggregation and magnetism of Cr, Mn, and Fe cations in GaN
• Backscattering Between Helical Edge States via Dynamic Nuclear Polarization
• Helical edge states coupled to a spin bath: Current-induced magnetization
• Electronic and optical properties of InAs/InAs${}_{0.625}$Sb${}_{0.375}$ superlattices and their application to far-infrared detectors
• Momentum-resolved spin splitting in Mn-doped trivial CdTe and topological HgTe semiconductors
• Dynamical separation of bulk and edge transport in HgTe-based 2D topological insulators
• Superexchange dominates in magnetic topological insulators
• Topological states in superlattices of HgTe-class materials for engineering three-dimensional flat bands
• Spin Texture and Mirror Chern number in Hg-Based Chalcogenides
• Interplay of quantum spin Hall effect and spontaneous time-reversal symmetry breaking in electron-hole bilayers I: Transport properties

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• Electronic and optical properties of InAs/InAs${}_{0.625}$Sb${}_{0.375}$ superlattices and their application to far-infrared detectors
• Fast electrically switchable large gap quantum spin Hall states in MGe${}_2$Z${}_4$
• Engineering axion insulator phase in superlattices with inversion symmetry breaking
• Spin-Hall conductivity and optical characteristics of noncentrosymmetric quantum spin Hall insulators: the case of PbBiI
• Edge Reconstruction in a Quantum Spin Hall Insulator