Proposal for valleytronic materials: Ferrovalley metal and valley gapless semiconductor

Abstract

Valleytronic materials can provide new degrees of freedom to future electronic devices. In this work, the concepts of the ferrovalley metal (FVM) and valley gapless semiconductor (VGS) are proposed, which can be achieved in valleytronic bilayer systems by electric field engineering. In valleytronic bilayer systems, the interaction between out-of-plane ferroelectricity and A-type antiferromagnetism can induce layer-polarized anomalous valley Hall (LP-AVH) effect. The K and −K valleys of FVM are both metallic, and electron and hole carriers simultaneously exist. In the extreme case, the FVM can become VGS by analogizing spin gapless semiconductor (SGS). Moreover, it is proposed that the valley splitting enhancement and valley polarization reversal can be achieved by electric field engineering in valleytronic bilayer systems. Taking the bilayer \mathrm{R}\mathrm{u}\mathrm{B}{\mathrm{r}}_2 as an example, our proposal is confirmed by the first-principle calculations. The FVM and VGS can be achieved in bilayer \mathrm{R}\mathrm{u}\mathrm{B}{\mathrm{r}}_2 by applying electric field. With appropriate electric field range, increasing electric field can enhance valley splitting, and the valley polarization can be reversed by flipping electric field direction. To effectively tune valley properties by electric field in bilayer systems, the parent monolayer should possess out-of-plane magnetization, and have large valley splitting. Our results shed light on the possible role of electric field in tuning valleytronic bilayer systems, and provide a way to design the ferrovalley-related material by electric field.

Graphical abstract

Keywords

valleytronics / electric field / bilayer

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Declarations

The authors declare that they have no competing interests and there are no conflicts.

Electronic supplementary materials

The online version contains supplementary material available at https://doi.org/10.1007/s11467-023-1334-y and https://journal.hep.com.cn/fop/EN/10.1007/s11467-023-1334-y.

Acknowledgements

This work was supported by Natural Science Basis Research Plan in Shaanxi Province of China (No. 2020JQ-845). Y.S.A. is supported by the Singapore Ministry of Education Academic Research Fund Tier 2 (Award No. MOE-T2EP50221-0019). We are grateful to Shanxi Supercomputing Center of China, and the calculations were performed on TianHe-2.

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