Chiral Pair Density Waves with Residual Fermi Arcs in RbV3Sb5

Abstract

The chiral 2 × 2 charge order has been reported and confirmed in the kagome superconductor RbV₃Sb₅, while its interplay with superconductivity remains elusive owing to its lowest superconducting transition temperature T_C of about 0.85 K in the AV₃Sb₅ family (A = K, Rb, Cs) that severely challenges electronic spectroscopic probes. Here, utilizing dilution-refrigerator-based scanning tunneling microscopy down to 30 mK, we observe chiral 2 × 2 pair density waves with residual Fermi arcs in RbV₃Sb₅. We find a superconducting gap of 150 μeV with substantial residual in-gap states. The spatial distribution of this gap exhibits chiral 2 × 2 modulations, signaling a chiral pair density wave (PDW). Our quasi-particle interference imaging of the zero-energy residual states further reveals arc-like patterns. We discuss the relation of the gap modulations with the residual Fermi arcs under the space-momentum correspondence between PDW and Bogoliubov Fermi states.