  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$^{'}$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 novel 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.
