Giant valley-polarized spin splittings in magnetized Janus Pt dichalcogenides

We reveal giant proximity-induced magnetism and valley-polarization effects in Janus Pt dichalcogenides (such as SPtSe), when bound to the europium oxide (EuO) substrate. Using first-principles simulations, it is surprisingly found that the charge redistribution, resulting from proximity with EuO, leads to the formation of two $K$ and $K^{\prime }$ valleys in the conduction bands. Each of these valleys displays its own spin polarization and a specific spin texture dictated by broken inversion and time-reversal symmetries, and valley-exchange and Rashba splittings as large as hundreds of meV. This provides a platform for exploring spin-valley physics in low-dimensional semiconductors, with potential spin transport mechanisms such as spin-orbit torques much more resilient to disorder and temperature effects.

Figure 1

(a) Top and side views of 1L ${\mathrm{PtSe}}_2$ (the black rectangle shows a unit cell). (b) Hexagonal Brillouin zone with high-symmetry points. Minimum energy configurations of (c) ${\mathrm{PtS}}_2$, (d) Janus SPtSe, and (e) 2L ${\mathrm{PtSe}}_2$ on a EuO substrate

Figure 2

(a), (c) Charge density difference (isovalue: $2.5\times {10}^{-3}$ electrons/${\mathrm{bohr}}^3$), and (b), (d) spin density (isovalue: $3.0\times {10}^{-3}$ electrons/${\mathrm{bohr}}^3$) of 1L ${\mathrm{PtS}}_2$ and Janus SPtSe on the EuO substrate, respectively. In (a), (c), blue and yellow colors represent charge accumulation and depletion, whereas in (b), (d), blue and yellow colors represent spin-up and spin-down densities, respectively.

Figure 3

(a), (c) Electronic band structure of 1L and 2L ${\mathrm{PtSe}}_2$ and (b), (d) Janus SPtSe on the EuO substrate, respectively. The SOC effects are included for each case.

Figure 4

2D spin textures of Janus 2L SPtSe on a EuO substrate. Refer to the brown lines in Fig. 3, where the inner contours correspond to valence bands passing through an energy $E=-0.85\mathrm{eV}$, whereas the outer contours (corners) belong to conduction bands passing through an energy $E=-0.20\mathrm{eV}$, respectively. The red/blue colors indicate spin up/down.