Influence of lattice termination on the edge states of the quantum spin Hall insulator monolayer $1{T}^{\ensuremath{'}}\text{\ensuremath{-}}{\mathrm{WTe}}_{2}$

Influence of lattice termination on the edge states of the quantum spin Hall insulator monolayer $1 T^{'} − {WTe}_{2}$

Alexander Lau, Rajyavardhan Ray, Dániel Varjas, and Anton R. Akhmerov

Phys. Rev. Materials 3, 054206 – Published 28 May 2019

Abstract

We study the influence of sample termination on the electronic properties of the novel quantum spin Hall insulator monolayer $1 T^{'} − {WTe}_{2}$ . For this purpose, we construct an accurate, minimal four-orbital tight-binding model with spin-orbit coupling by employing a combination of density-functional theory calculations, symmetry considerations, and fitting to experimental data. Based on this model, we compute energy bands and two-terminal conductance spectra for various ribbon geometries with different terminations, with and without a magnetic field. Because of the strong electron-hole asymmetry, we find that the edge Dirac point is buried in the bulk bands for most edge terminations. In the presence of a magnetic field, an in-gap edge Dirac point leads to exponential suppression of conductance as an edge Zeeman gap opens, whereas the conductance stays at the quantized value when the Dirac point is buried in the bulk bands. Finally, we find that disorder in the edge termination drastically changes this picture: the conductance of a sufficiently rough edge is uniformly suppressed for all energies in the bulk gap regardless of the orientation of the edge.

2 More

Received 14 January 2019

DOI:https://doi.org/10.1103/PhysRevMaterials.3.054206

Physics Subject Headings (PhySH)

Edge states Quantum spin Hall effect Quantum transport Topological materials

Monolayer films Nanoribbon Topological insulators Transition metal dichalcogenides

Density functional theory S-matrix method in transport Symmetries Tight-binding model

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Alexander Lau¹, Rajyavardhan Ray^2,3, Dániel Varjas^1,4, and Anton R. Akhmerov¹

¹Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 4056, 2600 GA Delft, The Netherlands
²Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
³Dresden Center for Computational Materials Science (DCMS), TU Dresden, 01062 Dresden, Germany
⁴QuTech, Delft University of Technology, P.O. Box 4056, 2600 GA Delft, The Netherlands