Engineering topological phases in triple HgTe/CdTe quantum wells

Abstract

Quantum wells formed by layers of HgTe between Hg${}_{1-x}$Cd${}_x$Te barriers lead to two-dimensional (2D) topological insulators, as predicted by the BHZ model. Here, we theoretically and experimentally investigate the characteristics of triple HgTe quantum wells. We describe such heterostructure with a three dimensional $8\times 8$ Kane model, and use its eigenstates to derive an effective 2D Hamiltonian for the system. From these we obtain a phase diagram as a function of the well and barrier widths and we identify the different topological phases composed by zero, one, two, and three sets of edge states hybridized along the quantum wells. The phase transitions are characterized by a change of the spin Chern numbers and their corresponding band inversions. Complementary, transport measurements are experimentally investigated on a sample close to the transition line between the phases with one and two sets of edges states. Accordingly, for this sample we predict a gapless spectrum with low energy bulk conduction bands given by one parabolic and one Dirac band, and with edge states immersed in the bulk valance bands. Consequently, we show that under these conditions, local and non-local transport measurements are inconclusive to characterize a sole edge state conductivity due to bulk conductivity. On the other hand, Shubnikov-de Haas (SdH) oscillations show an excellent agreement with our theory. Particularly, we show that the measured SdH oscillation frequencies agrees with our model and show clear signatures of the coexistence of a parabolic and Dirac bands.

15 pages, 5 figures

References in corpus (24)

• Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells
• Quantum Spin Hall Insulator State in HgTe Quantum Wells
• Discovery (theoretical prediction and experimental observation) of a large-gap topological-insulator class with spin-polarized single-Dirac-cone on the surface
• A topological Dirac insulator in a quantum spin Hall phase : Experimental observation of first strong topological insulator
• Unconventional Integer Quantum Hall effect in graphene
• First direct observation of Spin-textures in Topological Insulators : Spin-resolved ARPES as a probe of topological quantum spin Hall effect and Berry's phase
• Intrinsic and Rashba Spin-orbit Interactions in Graphene Sheets
• Nonlocal edge state transport in the quantum spin Hall state
• Quantum Spin Hall Effect in Inverted Type II Semiconductors
• Topological Surface States and Dirac point tuning in ternary Bi2Te2Se class of topological insulators
• Magnetic oscillations in planar systems with the Dirac-like spectrum of quasiparticle excitations II: transport properties
• Pressure and temperature driven phase transitions in HgTe quantum wells
• Persistence of two-dimensional topological insulator state in wide HgTe quantum well
• Devices with electrically tunable topological insulating phases
• Coexisting edge states and gapless bulk in topological states of matter
• Helical Liquids in Semiconductors
• Mesoscopic transport in two-dimensional topological insulators
• Topological insulators based on HgTe
• Layertronic control of topological states in multilayer metal-organic frameworks
• Topological excitonic corner states and nodal phase in bilayer quantum spin Hall insulators
• Robust helical edge transport at $\nu =0$ quantum Hall state
• Two-dimensional topological insulator state in double HgTe quantum well
• Massive and topological surface states in tensile strained HgTe
• Multiple crossing of Landau levels of two-dimensional fermions in double HgTe quantum wells

Cited by in corpus (7)

• Direct observation of topological surface state in the topological superconductor 2M-WS2
• Energy states of Rydberg excitons in finite crystals: From weak to strong confinement
• Quantum oscillations in 2D electron gases with spin-orbit and Zeeman interactions
• Unconventional quantum oscillations and evidence of nonparabolic electronic states in quasi-two-dimensional electron system at complex oxide interfaces
• Interaction-controlled transport in a two-dimensional massless-massive Dirac system: Transition from degenerate to nondegenerate regimes
• Tunable Competing Electronic Orders in Double Quantum Spin Hall Superlattices
• Engineering Majorana Kramers Pairs In Synthetic High Spin Chern Insulators