Abstract
Large-gap quantum spin Hall insulators are promising materials for room-temperature applications based on Dirac fermions. Key to engineer the topologically non-trivial band ordering and sizable band gaps is strong spin-orbit interaction. Following Kane and Mele’s original suggestion, one approach is to synthesize monolayers of heavy atoms with honeycomb coordination accommodated on templates with hexagonal symmetry. Yet, in the majority of cases, this recipe leads to triangular lattices, typically hosting metals or trivial insulators. Here, we conceive and realize “indenene”, a triangular monolayer of indium on SiC exhibiting non-trivial valley physics driven by local spin-orbit coupling, which prevails over inversion-symmetry breaking terms. By means of tunneling microscopy of the 2D bulk we identify the quantum spin Hall phase of this triangular lattice and unveil how a hidden honeycomb connectivity emerges from interference patterns in Bloch px ± ipy-derived wave functions.
Highlights
Large-gap quantum spin Hall insulators are promising materials for room-temperature applications based on Dirac fermions
The following tight-binding Hamiltonian captures the low-energy electronic structure of any realistic implementation, as we will see later in the density functional theory (DFT) calculations for indenene on SiC(0001). The latter is the actual material realization that we propose here and our modeling allows us to precisely determine the conditions under which its quantum spin Hall insulator (QSHIs) phase is realized
In the freestanding triangular layer (Fig. 2a, d) the D6h point symmetry yields Dirac-crossings of the p± in-plane orbitals at K/K′ and prohibits the hybridization with the pz subspace resulting in a metallic phase
Summary
Large-gap quantum spin Hall insulators are promising materials for room-temperature applications based on Dirac fermions. We realize a triangular lattice of indium on SiC(0001) with topological band inversion at the valley momenta K/K′.
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