Topological superconductivity in Janus monolayer transition metal dichalcogenides

The Janus monolayer transition metal dichalcogenides(TMDs)MXY(M=Mo,W,etc.and X,Y=S,Se,etc.)have been successfully synthesized in recent years.The Rashba spin splitting in these compounds arises due to the breaking of out-of-plane mirror symmetry.Here we study the pairing symmetry of superconducting Janus monolayer TMDs within the weak-coupling framework near critical temperature Tc,of which the Fermi surface(FS)sheets centered around bothΓand K(K′)points.We find that the strong Rashba splitting produces two kinds of topological superconducting states which differ from that in its parent compounds.More specifically,at relatively high chemical potentials,we obtain a timereversal invariant s+f+p-wave mixed superconducting state,which is fully gapped and topologically nontrivial,i.e.,a Z_(2) topological state.On the other hand,a time-reversal symmetry breaking d+p+f-wave superconducting state appears at lower chemical potentials.This state possess a large Chern number|C|=6 at appropriate pairing strength,demonstrating its nontrivial band topology.Our results suggest the Janus monolayer TMDs to be a promising candidate for the intrinsic helical and chiral topological superconductors.