Impact of charge density waves on superconductivity and topological properties in kagome superconductors

We investigate the electronic structure and superconducting gaps in the charge density wave (CDW) states of kagome superconductors, focusing on the concurrent presence of CDW and superconducting orders. Two predominant CDW configurations are explored, the trihexagonal (TrH) and star-of-David (SoD) patterns, involving charge bond order (CBO) and chiral flux phase (CFP), corresponding to real and imaginary bond orders. In the isotropic $s$-wave superconducting state, the presence of CBO alone maintains an isotropic superconducting gap, whereas the introduction of CFP induces anisotropy in the gap, manifesting time-reversal symmetry breaking due to the CFP. Our analysis extends to the topological properties of these states, revealing a marked topological phase transition in the TrH configuration from a trivial to a nontrivial state with increasing CFP intensity. This transition suggests that the introduction of CFP could catalyze the emergence of topological superconductivity, potentially leading to the presence of Majorana excitations. The results contribute significantly to understanding the complex interplay between various CDW patterns and superconductivity in kagome superconductors. They provide a theoretical framework for the diverse experimental observations of energy gaps and open different avenues for research into topological superconductivity and its potential applications. This paper underscores the necessity for further experimental and theoretical exploration to unveil additional intertwined quantum states and functionalities in these intriguing materials.