Coexistence of superconductivity and topological phase in kagome metals CsTi3Te3X2 (X = Bi, Sb, Se, Sn): A first-principles investigation

The AV3Sb5-prototype (A = K, Rb, Cs) kagome materials have garnered significant research interest owing to their diverse properties. Most studies have primarily concentrated on the kagome layers, neglecting the influence of the honeycomb layers on the material properties. We design a series of materials with partial replacement of honeycomb layer atoms CsTi3Te3X2 (X = Bi, Sb, Se, Sn) through first-principles calculations. Calculations of ab initio molecular dynamics and phonon dispersion indicate that this family of materials is stable and may be experimentally synthesized in the future. Compared with the topologically trivial original material CsTi3Te5, the calculated results reveal diverse physical properties in these materials, including stronger electron–phonon coupling, relatively high superconducting critical temperature, and topological surface state features, where the doped honeycomb layers play indispensable roles. By reducing the symmetry of the system through doping, the parity of the band near the Fermi level can be changed, and the nontrivial topological surface state can be further changed. Our work provides a brand approach to studying the regulation of various properties in kagome systems.