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arXiv · 2005.02519

The Sign of Three: Spin/Charge Density Waves at the Boundaries of Transition Metal Dichalcogenides

Sridevi Krishnamurthi·Geert Brocks
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Abstract

One-dimensional grain boundaries of two-dimensional semiconducting {\MX} (M= Mo,W; X=S,Se) transition metal di-chalcogenides are typically metallic at room temperature. The metallicity has its origin in the lattice polarization, which for these lattices with $D_{3h}$ symmetry is a topological invariant, and leads to one-dimenional boundary states inside the band gap. For boundaries perpendicular to the polarization direction, these states are necessarily 1/3 occupied by electrons or holes, making them susceptible to a metal-insulator transition that triples the translation period. Using density-functional-theory calculations we demonstrate the emergence of combined one-dimensional spin density/charge density waves of that period at the boundary, opening up a small band gap of $\sim 0.1$ eV. This unique electronic structure allows for soliton excitations at the boundary that carry a fractional charge of $\pm 1/3\ e$.

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Sridevi Krishnamurthi, Geert Brocks. 2020-05-05. The Sign of Three: Spin/Charge Density Waves at the Boundaries of Transition Metal Dichalcogenides. https://doi.org/10.1103/physrevb.102.161106

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