Tunable metallic and topological properties in two-dimensional ligand-functionalized antimonene films

Abstract

Using first-principle calculations, we predict that fully-hydroxyl-decorated antimonene (SbOH) is a two-dimensional topological insulator with extraordinarily global gap of 330 meV, and incompletely hydroxyl-decorated antimonene films show metallic properties. The ligand OH on top side of SbOH@SiC(1 1 1) heterostructure can be veered by external electric field, which induces a switchable in-plane spontaneous polarization. Moreover, the asymmetry and strong spin-orbit coupling of SbOH leads to spin polarization of edge states and a pair of unequal valleys that have opposite Berry curvatures near the vertices (K and K’) of Brillouin zone. The tunable of valley polarization in SbOH is useful to realize quantum valley Hall effect. In the case, SbOH shows the dual TI with coexisting switchable ferroelectric and valley polarization. Ferroelectric topological materials provide a new paradigm for device engineering, such as perfect-focusing Veselago lens and spin-selective electron collimator. Based on spin polarization of edge states, we suggest a transistor model using the spin direction as a switch. We can tune the material to be metal, TI, or ferroelectric TI according to SbO film partially or completely hydroxylated. Our findings not only broaden the family of the 2D ferroelectric topological materials, but also offer a promising platform for novel electronic and spintronic applications.