Emergence of ferroelectricity and spin-valley properties in   two-dimensional honeycomb binary compounds
  By means of density functional theory calculations, we predict that several two dimensional AB binary monolayers, where A and B atoms belong to group IV or III-V, are ferroelectric. Dipoles arise from the buckled structure, where the A and B ions are located on the sites of a bipartite corrugated honeycomb lattice with trigonal symmetry. We discuss the emerging valley-dependent properties and the coupling of spin and valley physics, which arise from the loss of inversion symmetry, and explore the interplay between ferroelectricity and Rashba spin-spitting phenomena. We show that valley-related properties originate mainly from the binary nature of AB monolayers, while the Rashba spin-texture developing around valleys is fully controllable and switchable by reversing the ferroelectric polarization. 
Domenico Di Sante, Alessandro Stroppa, Paolo Barone, Myung-Hwan   Whangbo and Silvia Picozzi
cond-mat.mtrl-sci cond-mat.mes-hall