Proximity-induced spin-valley polarization in silicene or germanene on F-doped WS2

Silicene and germanene are key materials for the field of valleytronics. However, interaction with the substrate, which is necessary to support the electronically active medium, becomes a major obstacle. In the present work, we propose a substrate (F-doped ${\mathrm{WS}}₂$) that avoids detrimental effects and at the same time induces the required valley polarization, so that no further steps are needed for this purpose. The behavior is explained by proximity effects on silicene or germanene, as demonstrated by first-principles calculations. Broken inversion symmetry due to the presence of ${\mathrm{WS}}₂$ opens a substantial band gap in silicene or germanene. F doping of ${\mathrm{WS}}₂$ results in spin polarization, which, in conjunction with proximity-enhanced spin-orbit coupling, creates sizable spin-valley polarization.