Majorana edge states in s-wave kagome superconductors with Rashba interaction

Abstract: We study kagome lattices with on-site and extended spin-singlet s-wave superconducting pairing and show that the inclusion of Rashba spin-orbit (RSO) interaction allows time-reversal-invariant topological superconducting states which support helical Majorana pairs at the edge. We calculate the Z2 topological invariant as a function of the pairing parameters for different chemical potentials. The rich phase diagrams reveal topological, nodal, and trivial superconducting states depending on the system parameters. We also consider a 2X2 time-reversal symmetry-breaking chiral flux phase, which has been demonstrated to be energetically favorable in the AV3Sb5 family of superconductors. Incorporating such symmetry-breaking order in our model leads to chiral Majorana edge states defined by a Chern number. We show how the RSO interaction allows for topological phases with even and odd Chern numbers for different system parameters. This work demonstrates how a simple s-wave kagome superconductor with RSO interaction can support helical and chiral Majorana edge states, and motivates the search for Majorana fermions in kagome superconductors.