Coexistence of superconductivity and topological phase in kagome metals ANb3Bi5 (A = K, Rb, Cs)

The A V 3 Sb 5 prototype kagome materials have been demonstrated as a versatile platform for exploring exotic properties in condensed matter physics, including charge density waves, superconductivity, non-trivial electron topology, as well as topological superconductivity. Here we identify that A Nb 3 Bi 5 ( A = K, Rb, Cs) exhibit non-trivial coexisting superconductivity and topological properties via first-principles calculations. The negative formation energy and the absence of imaginary phonon dispersion demonstrate both thermodynamics and dynamics stabilities of A Nb 3 Bi 5 ( A = K, Rb, Cs) under ambient conditions. By analytically solving the Allen-Dynes-modified McMillan formula, the superconducting transition temperatures are predicted to be 2.11, 2.15 and 2.21 K for KNb 3 Bi 5 , RbNb 3 Bi 5 , and CsNb 3 Bi 5 , respectively. More importantly, the kagome materials proposed here can be classified into Z₂ Z 2 topological metals due to the non-trivial topological index and the obvious surface states around the Fermi level. Such coexistence of superconductivity and non-trivial band characters in A Nb 3 Bi 5 ( A = K, Rb, Cs) offer us more insights to study the relationship between superconductivity and topological properties, and to design innate topological superconductors.