Using ferroelectric polarization to regulate and preserve the valley polarization in a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>HfN</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow><mml:mo>/</mml:mo><mml:mrow><mml:msub><mml:mi>CrI</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow><mml:mo>/</mml:mo><mml:mrow><mml:msub><mml:mi>In</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Se</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math> heterotrilayer
Baoxing Zhai, Ruiqing Cheng, Wen Yao, Lei Yin, Chenhai Shen, Congxin Xia, Jun He
Abstract
How to effectively regulate and preserve valley polarization is very important for the development of valleytronic devices in practical applications. Here, we propose a scheme of using ferroelectric polarization reversal to control valley polarization and, further, using ferroelectric nonvolatility to stably preserve the regulated valley state. We design a trilayer heterostructure, which is composed of vertically stacked two-dimensional (2D) valleytronic material ${\mathrm{HfN}}_{2}$, 2D ferromagnetic material ${\mathrm{CrI}}_{3}$, and 2D ferroelectric material ${\mathrm{In}}_{2}{\mathrm{Se}}_{3}$. Through first-principles simulation, we find that the polarization reversal of ${\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ can change the orientation of the easy magnetization axis for ${\mathrm{CrI}}_{3}$, and the change of magnetic moment direction causes the change of valley polarization for ${\mathrm{HfN}}_{2}$. When ${\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ is polarized upward, the easy magnetization axis of ${\mathrm{CrI}}_{3}$ is the $z$ axis, and the valley polarization is 15 meV, while when ${\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ is polarized downward, the easy magnetization axis of ${\mathrm{CrI}}_{3}$ is changed to the $x\text{\ensuremath{-}}y$ plane, and the valley polarization is changed to zero. Then we study the ferroelectric bistability of the ${\mathrm{HfN}}_{2}/{\mathrm{CrI}}_{3}/{\mathrm{In}}_{2}{\mathrm{Se}}_{3}$ heterotrilayer and propose a method to preserve different valley states using ferroelectric nonvolatility.