Using in-plane anisotropy to engineer Janus monolayers of rhenium dichalcogenides

Abstract

The new class of Janus two-dimensional (2D) transition-metal dichalcogenides with two different interfaces are currently gaining increasing attention due to their distinct properties different from the typical 2D materials. Here, we show that in-plane anisotropy of a 2D atomic crystal, like ReS${}_2$ or ReSe${}_2$, allows formation of a large number of inequivalent Janus monolayers. We use first-principles calculations to investigate the structural stability of 29 distinct ReX${}_{2-x}$Y${}_x$ ($\mathrm{X},\mathrm{Y}\in \{\mathrm{S},\mathrm{Se}\}$) structures, which can be obtained by selective exchange of exposed chalcogens in a ReX${}_2$ monolayer. We also examine the electronic properties and work function of the most stable Janus monolayers and show that the large number of inequivalent structures provides a way to engineer spin-orbit splitting of the electronic bands. We find that the breaking of inversion symmetry leads to sizable spin splittings and spontaneous diople moments than are larger than those in other Janus dichalcogenides. Moreover, our caluclations suggest that the work function of the Janus monolayers can be tuned by varying the content of the substituting chalcogen. Our work demonstrates that in-plane anisotropy provides additional flexibility in sub-layer engineering of 2D atomic crystals.

References in corpus (7)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Advanced capabilities for materials modelling with Quantum ESPRESSO
• Accurate and efficient algorithm for Bader charge integration
• Quantum Spin Hall Effect and Topological Field Effect Transistor in Two-Dimensional Transition Metal Dichalcogenides
• Synthesis of epitaxial monolayer Janus SPtSe
• Visualizing Orbital Content of Electronic Bands in Anisotropic 2D Semiconducting ReSe${}_2$
• Interplay of crystal thickness and in-plane anisotropy and evolution of quasi-one dimensional electronic character in ReSe${}_2$