Chiral pair density waves with residual Fermi arcs in RbV3Sb5

TL;DR

This study uses ultra-low temperature STM to reveal chiral pair density waves and residual Fermi arcs in the superconductor RbV3Sb5, providing insights into its unconventional superconducting state.

Contribution

First direct observation of chiral pair density waves and residual Fermi arcs in RbV3Sb5 using ultra-low temperature STM.

Findings

Chiral 2x2 pair density waves detected in RbV3Sb5.

Residual Fermi arcs observed in the superconducting state.

Superconducting gap of 150 μeV with in-gap states.

Abstract

The chiral 2 by 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 Tc of about 0.85K among the AV3Sb5 family (A=K, Rb, Cs) that severely challenges electronic spectroscopic probes. Here, utilizing dilution-refrigerator-based scanning tunneling microscopy (STM) down to 30mK, we observe chiral 2 by 2 pair density waves with residual Fermi arcs in RbV3Sb5. We find a superconducting gap of 150{\mu}eV with substantial residual in-gap states. The spatial distribution of this gap exhibits chiral 2 by 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.