Two-dimensional ligand-functionalized Plumbene: A promising candidate for Ferroelectric and Topological Order with a Large Bulk Band Gap

Multifunctional two-dimensional (2D) materials has been attracted attentions to explore due to their versatile applications in electronic devices. Ferroelectric and topological materials have separately attracted investigated recently. However, materials with two properties coexisting are little known. 2D materials with coexisting topological and ferroelectric ordering have been the focus of 2D condensed matter physics in recent years, and their interaction in a single system may make important untapped phenomena and applications possible. Here, based on first-principles calculations, we demonstrate a class of ferroelectric topological insulators (FETIs) in CH2OCH3-functionalized plumbene (Pb–CH2OCH3). We find that the large nontrivial band gap of Pb–CH2OCH3 reaching 0.80 eV, which is introduced by the orbital filtering effect in the presence of spin-orbit coupling (SOC). Noticeably, the in-plane spontaneous polarization can be engineered by rotating the CH2OCH3 molecule at the surface of Plumbene. These results on the combination of topological and ferroelectric properties may provide a new platform for the development of microelectronic devices and the application of spintronics at room temperature.