Interplay of superconductivity and charge-density-wave order in kagome materials

The family of Kagome metals AV₃Sb₅ with A = K, Rb, Cs has attracted a lot of attention recently for the wealth of exotic phases its members exhibit. In particular, all three members enter an unconventional charge-density-wave phase at ~100 K characterized by a 2x2 in-plane modulation, whose exact nature, specifically whether it breaks additional point-group or time-reversal symmetries in the form of loop-currents, is yet to be determined unambiguously. Importantly, all three members also become superconducting below a critical temperature of ~1-3 K. Despite extensive research, the symmetry of the superconducting order parameter remains disputed, with experiments seemingly supporting different conclusions. As key aspects of the physics might lie in the intertwining of electronic orders, a better understanding of the impact of the CDW on superconductivity is crucial. We derive a Ginzburg-Landau free energy to study the interplay of different pairing channels with charge-density-wave orders as effective fields. Our results shed light on how the superconducting state mimics the broken symmetries of the charge order and can guide future microscopic calculations and the experimental identification of the superconducting state in the kagome superconductors.