# Electrically tunable polarizer based on two-dimensional orthorhombic ferrovalley materials

## TL;DR

This paper introduces a new type of ferrovalley material with orthorhombic lattice, enabling electrically tunable polarization control of light, which advances valleytronic device applications.

## Contribution

It proposes and demonstrates a novel orthorhombic ferrovalley material that allows electric field control of light polarization, differing from previous hexagonal ferrovalley materials.

## Key findings

- Linearly polarized optical selectivity for valleys in orthorhombic ferrovalley materials.
- Prototype of an electrically tunable polarizer based on these materials.
- Potential to emit circularly polarized light with specific chirality.

## Abstract

The concept of ferrovalley materials has been proposed very recently. The existence of spontaneous valley polarization, resulting from ferromagnetism, in such hexagonal two-dimensional materials makes nonvolatile valleytronic applications realizable. Here, we introduce a new member of ferrovalley family with orthorhombic lattice, i.e. monolayer group-IV monochalcogenides (GIVMs), in which the intrinsic valley polarization originates from ferroelectricity, instead of ferromagnetism. Combining the group theory analysis and first-principles calculations, we demonstrate that, different from the valley-selective circular dichroism in hexagonal lattice, linearly polarized optical selectivity for valleys exists in the new type of ferrovalley materials. On account of the distinctive property, a prototype of electrically tunable polarizer is realized. In the ferrovalley-based polarizer, a laser beam can be optionally polarized in x- or y-direction, depending on the ferrovalley state controlled by external electric fields. Such a device can be further optimized to emit circularly polarized radiation with specific chirality and to realize the tunability for operating wavelength. Therefore, we show that two-dimensional orthorhombic ferrovalley materials are the promising candidates to provide an advantageous platform to realize the polarizer driven by electric means, which is of great importance in extending the practical applications of valleytronics.

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Source: https://tomesphere.com/paper/1706.06374