A possible way to achieve anomalous valley Hall effect by piezoelectric effect in \(\mathrm{GdCl_2}\) monolayer

• Published in: arXiv.org
• Main Authors: San-Dong, Guo, Jing-Xin, Zhu, Wen-Qi, Mu, Bang-Gui, Liu
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 28.09.2021
• Subjects: Compressive properties; Conduction bands; Coupling; Electric fields; Electromagnetism; Ferromagnetism; First principles; Hall effect; Magnetic anisotropy; Magnetism; Materials selection; Mathematical analysis; Monolayers; Piezoelectricity; Plane strain; Polarization; Splitting; Valence band; Valleys
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2109.13534

Ferrovalley materials can achieve manipulation of the valley degree of freedom with intrinsic spontaneous valley polarization introduced by their intrinsic ferromagnetism. A good ferrovalley material should possess perpendicular magnetic anisotropy (PMA), valence band maximum (VBM)/conduction band minimum (CBM) at valley points, strong ferromagnetic (FM) coupling and proper valley splitting. In this work, the monolayer \(\mathrm{GdCl_2}\) is proposed as a potential candidate material for valleytronic applications by the first-principles calculations. It is proved that monolayer \(\mathrm{GdCl_2}\) is a FM semiconductor with the easy axis along out of plane direction and strong FM coupling. A spontaneous valley polarization with a valley splitting of 42.3 meV is produced due to its intrinsic ferromagnetism and spin orbital coupling (SOC). Although the VBM of unstrained monolayer \(\mathrm{GdCl_2}\) is away from valley points, a very small compressive strain (about 1\%) can make VBM move to valley points. We propose a possible way to realize anomalous valley Hall effect in monolayer \(\mathrm{GdCl_2}\) by piezoelectric effect, not an external electric field, namely piezoelectric anomalous valley Hall effect (PAVHE). This phenomenon could be classified as piezo-valleytronics, being similar to piezotronics and piezophototronics. The only independent piezoelectric strain coefficient \(d_{11}\) is -2.708 pm/V, which is comparable to one of classical bulk piezoelectric material \(\alpha\)-quartz (\(d_{11}\)=2.3 pm/V). The biaxial in-plane strain and electronic correlation effects are considered to confirm the reliability of our results. Finally, the monolayer \(\mathrm{GdF_2}\) is predicted to be a ferrovalley material with dynamic and mechanical stabilities, PMA, VBM at valley points, strong FM coupling, valley splitting of 47.6 meV, and \(d_{11}\) of 0.584 pm/V.