Tetragonal transition metal dichalcogenides with diverse electronic properties

Hexagonal transition metal dichalcogenides (TMDCs) represent a famous material family with rich structural phases and elemental compositions, whose diverse electronic properties, like magnetism, topological property, and superconductivity (SC), spark promising applications in the interdisciplinary field of ``XX-tronics''. Here we found tetragonal TMDCs with distorted Lieb (dLieb) lattice present similar electronic properties as hexagonal TMDCs, by demonstrating the stability of transition metal diselenides (dLieb-MSe₂) and ditellurides (dLieb-MTe₂) with semiconductivity, half-metallicity, magnetic metallicity, topological electronic states, or phonon-mediated SC. Specifically, dLieb-TiSe₂ and dLieb-TiTe₂ are semiconductors, whereas partial occupation of localized d_z² states induces Stoner magnetism in dLieb-MSe₂ (M=Nb, V, Cr) with half-metallicity and in dLieb-MnSe₂ with metallicity. Notably, as the only TMDC monolayer with the magnetism stemming from Nb atom, dLieb-NbSe₂ monolayer was found exhibiting exotic chiral topological edge states. The Stoner magnetism will be suppressed in dLieb-FeSe₂ monolayer with fully occupied d_z² states, which could enable phonon-mediated SC with a transition temperature TC~4 Kelvin. Together with our previously proposed disulfides dLieb-MS₂, this work provides an overview table for tetragonal TMDCs with diverse electronic properties, which appear as promising alternatives for hexagonal TMDCs in the application of ``XX-tronics''.