Topological superconductivity of line defects in transition metal dichalcogenides

Convincing signatures of Majorana zero modes (MZMs) are one necessary requirement for achieving fault-tolerant quantum computations based on topological superconductivity (TSC). In addition to improving fabrication techniques, exploring the stoichiometric TSC platform is another route to suppressing the influences of trivial in-gap modes on the signatures of MZMs. Stoichiometric transition metal dichalcogenides (TMD) with topological surface states (TSSs) are promising but the field range of inducing magnetic vortices to harbor MZMs is limited by the small perpendicular upper critical field. Here, we propose that the line defects of chalcogen vacancies (CVs) embedded in TMDs are the stoichiometric TSC candidates for realizing stable MZMs without needing the TSSs under a wide range of in-plane magnetic fields. Detailed analysis and calculations on the 1H-$\mathrm{Mo}{X}₂$, 1H-$\mathrm{W}{X}₂$, and 1T-$\mathrm{Pt}{X}₂$ ($X=S$, Se, or Te) monolayers with CV line defects indicate the antisymmetric spin-orbit coupling effect, known as the origin of odd-parity pairing, is ensured by noncentrosymmetric point group symmetry. First-principles TSC phase diagrams are constructed to facilitate experimental detection of convincing signatures for the MZMs located at both ends of the line defect. Our findings enrich the stoichiometric TSC candidates and will promote device fabrication to manipulating and storing quantum information based on the device-friendly TMDs.