Ultrastrong coupling between polar distortion and optical properties in ferroelectric MoBr$_2$O$_2$

TL;DR

This study demonstrates that the layered compound MoBr$_2$O$_2$ exhibits ultrastrong coupling between polar distortion and optical/electronic properties, enabling multiple tunable functionalities via external stimuli, with potential applications in energy and information technologies.

Contribution

The paper reveals for the first time that MoBr$_2$O$_2$ exhibits ultrastrong coupling between polar distortion and optical properties, enabling multi-property tunability within a single material.

Findings

Demonstrates electric-field switchable polarization in MoBr$_2$O$_2$.

Shows ultrastrong coupling between polar distortion and optical/electronic properties.

Reveals large photostrictive effect and multiple tunable optical phenomena.

Abstract

Tuning the properties of materials using external stimuli is crucial for developing versatile smart materials. A strong coupling among order parameters within a single-phase material constitutes a potent foundation for achieving precise property control. However, cross-coupling is pretty weak in most single materials. Leveraging first principles calculations, we demonstrate the layered mixed anion compound MoBr$_2$O$_2$ exhibits electric-field switchable spontaneous polarization and ultrastrong coupling between polar distortion and electronic structures as well as optical properties. It offers feasible avenues of achieving tunable Rashba spin-splitting, electrochromism, thermochromism, photochromism, and nonlinear optics by applying an external electric field to a single domain sample, heating, as well as intense light illumination. Additionally, it exhibits an exceptionally large photostrictive effect. These findings not only showcase the feasibility of achieving multiple order parameter coupling within a single material, but also pave the way for comprehensive applications based on property control, such as energy harvesting, information processing, and ultrafast control.