Electrically Tunable Polarizer based on 2D Orthorhombic Ferrovalley Materials*

The concept of ferrovalley materials has been proposed recently. The existence of spontaneous valley polarization, resulting from ferromagnetism in hexagonal 2D materials makes nonvolatile valleytronic applications realizable. Here we introduce a new member of ferrovalley family with orthorhombic lattice, i.e. group-IV monochalcogenides, where intrinsic valley polarization originates from ferroelectricity. We demonstrate linearly polarized optical selectivity for valleys exists in the new ferrovalley materials. A prototype of electrically tunable polarizer is then realized. In the polarizer, a laser beam can be optionally polarized in x- or y-direction, depending on the ferrovalley state controlled by electric fields. Such a device can be further optimized to emit circularly polarized light and to realize the tunable wavelength. Therefore, 2D orthorhombic ferrovalley materials are the promising candidates to provide an advantageous platform to realize the polarizer driven by electric means, which is important in extending the practical applications of valleytronics.