The mirror asymmetry induced nontrivial properties of polar WSSe/MoSSe heterostructures.

Janus MoSSe and WSSe as new members to the family of transitional metal dichalcogenides (TMDCs) present intriguing properties that absent in its parent MX 2 (M  =  Mo, W; X  =  S, Se, Te) monolayers due to the out-of-plane mirror asymmetry. For WSSe/MoSSe van der Waals (vdW) heterostructures, intralayer/interlayer potential drops lead to significantly larger band offset than MX 2 heterobilayers, ensuring the long lifetimes for valley polarized interlayer excitons. Regard to the spin-valley-layer locking effects in WSSe/MoSSe vdW heterostructures, the band offset larger than the Zeeman-type spin splitting guarantees effective interlayer hopping and, therefore, large degree of valley polarization. Rashba-type spin splitting can coexist with the valley spin splitting and thus add the carrier transport paths, and intralayer/interlayer potential drops show obvious effects on the Rashba parameter. According to these results, WSSe/MoSSe vdW heterostructures manifest themselves the most promising candidates for spintronics and valleytronics with superiorities to the MX2 counterparts.