• DOI:10.1039/D1CP05337J
• Corpus ID: 239769145

Valley polarization transition driven by biaxial strain in Janus GdClF monolayer.

@article{Guo2021ValleyPT,
  title={Valley polarization transition driven by biaxial strain in Janus GdClF monolayer.},
  author={San-Dong Guo and Xiao-Shu Guo and Xiu-Xia Cai and Banggui Liu},
  journal={Physical chemistry chemical physics : PCCP},
  year={2021}
}

• San-Dong Guo, Xiao-Shu Guo, +1 author Banggui Liu
• Published 23 October 2021
• Physics
• Physical chemistry chemical physics : PCCP

The valley degree of freedom of carriers in crystals is useful to process information and perform logic operations, and it is a key factor for valley application to realize valley polarization. Here, we propose a model that the valley polarization transition at different valley points (-K and K points) is produced by biaxial strain. Using first-principles calculations, we illustrate our idea with a concrete example of a Janus GdClF monolayer. The predicted GdClF monolayer is dynamically, mechanically and thermally stable, and is a ferromagnetic (FM) semiconductor with perpendicular magnetic anisotropy (PMA), valence band maximum (VBM) at valley points and a high Curie temperature (TC). Due to its intrinsic ferromagnetism and spin-orbit coupling (SOC), a spontaneous valley polarization will be induced, but the valley splitting is only -3.1 meV, which provides an opportunity to achieve valley polarization transition at different valley points by strain. In the considered strain range (a/a0: 0.94-1.06), the strained GdClF monolayer always has an energy bandgap, strong FM coupling and PMA. The compressive strain is in favour of -K valley polarization, while the tensile strain is favorable for K valley polarization. The corresponding valley splittings at 0.96 and 1.04 strains are -44.5 meV and 29.4 meV, respectively, which are higher than the thermal energy at room temperature (25 meV). Due to its special Janus structure, both in-plane and out-of-plane piezoelectric polarizations can be observed. It is found that the direction of in-plane piezoelectric polarization can be overturned by strain, and the d11 values at 0.96 and 1.04 strains are -1.37 pm V-1 and 2.05 pm V-1, respectively. Our work paves the way to design ferrovalley materials for application in multifunctional valleytronic and piezoelectric devices by strain.