Unconventional quantized edge transport in the presence of inter-edge coupling in intercalated graphene

TL;DR

This paper demonstrates that quantized edge transport and quantum spin Hall effects can persist despite inter-edge coupling in Ta-intercalated graphene, due to orbital-dependent edge state decay.

Contribution

It reveals that inter-edge coupling does not necessarily destroy QSH effects, highlighting the role of orbital-dependent decay in maintaining edge states.

Findings

Quantized edge transport persists with inter-edge coupling.

Only one pair of edge states maintains their edge state feature.

The non-trivial gap is 81 meV, indicating robust topological properties.

Abstract

It is generally believed that the inter-edge coupling destroys the quantum spin Hall (QSH) effect along with the gap opening at the Dirac points. Using first-principles calculations, we find that the quantized edge transport persists in the presence of inter-edge coupling in Ta intercalated epitaxial graphene on SiC(0001), being a QSH insulator with the non-trivial gap of 81 meV. In this case, the band is characterized by two perfect Dirac cones with different Fermi velocities, yet only one maintains the edge state feature. We attribute such an anomalous behavior to the orbital-dependent decay of edge states into the bulk, which allows the inter-edge coupling just between one pair of edge states rather than two.