Probing topological transitions in HgTe/CdTe quantum wells by magneto-optical measurements

Abstract

In two-dimensional topological insulators, such as inverted HgTe/CdTe quantum wells, helical quantum spin Hall (QSH) states persist even at finite magnetic fields below a critical magnetic field $B_{\mathrm{c}}$, above which only quantum Hall (QH) states can be found. Using linear-response theory, we theoretically investigate the magneto-optical properties of inverted HgTe/CdTe quantum wells, both for infinite two-dimensional and finite-strip geometries, and possible signatures of the transition between the QSH and QH regimes. In the absorption spectrum, several peaks arise due to non-equidistant Landau levels in both regimes. However, in the QSH regime, we find an additional absorption peak at low energies in the finite-strip geometry. This peak arises due to the presence of edge states in this geometry and persists for any Fermi level in the QSH regime, while in the QH regime the peak vanishes if the Fermi level is situated in the bulk gap. Thus, by sweeping the gate voltage, it is possible to experimentally distinguish between the QSH and QH regimes due to this signature. Moreover, we investigate the effect of spin-orbit coupling and finite temperature on this measurement scheme.

arXiv comment14 pages, 13 figures

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Cited by in corpus (12)

• Magnetic field effects on edge and bulk states in topological insulators based on HgTe/CdHgTe quantum wells with strong natural interface inversion asymmetry
• Testing Topological Protection of Edge States in Hexagonal Quantum Spin Hall Candidate Materials
• Photogalvanic effect in HgTe/CdTe topological insulator due to edge-bulk optical transitions
• Terahertz detection of magnetic field-driven topological phase transition in HgTe-based transistors
• Non-linear ballistic response of quantum spin-Hall edge states
• Tunable spin-polarized edge transport in inverted quantum-well junctions
• Topological phase transitions in an inverted InAs/GaSb quantum well driven by tilted magnetic fields
• Faraday rotation and transmittance as markers of topological phase transitions in 2D materials
• Edge states in proximitized graphene ribbons and flakes in a perpendicular magnetic field: emergence of lone pseudohelical pairs and pure spin-current states
• Quantum revivals in HgTe/CdTe quantum wells and topological phase transitions
• Magnetotransport properties of the Quantum Spin Hall and Quantum Hall states in an inverted HgTe/CdTe and InAs/GaSb quantum wells
• The birefringent spin-laser as a system of coupled harmonic oscillators