Chiral kagome superconductivity modulations with residual Fermi arcs in KV3Sb5 and CsV3Sb5

TL;DR

This study reveals chiral pair density wave modulations with residual Fermi arcs in KV3Sb5 and CsV3Sb5 superconductors, demonstrating a novel form of superconductivity with broken time-reversal symmetry and orbital selectivity, using advanced scanning tunneling microscopy techniques.

Contribution

It provides the first experimental evidence of chiral PDW order with orbital selectivity and residual Fermi arcs in kagome superconductors, linking these phenomena to finite momentum pairing and charge order.

Findings

Observation of chiral 2x2 spatial modulations in the superconducting gap.

Detection of residual Fermi arcs linked to reconstructed d-orbital states.

Identification of a chiral pair density wave breaking time-reversal symmetry.

Abstract

Superconductivity involving finite momentum pairing can lead to spatial gap and pair density modulations, as well as Bogoliubov Fermi states within the superconducting gap. However, the experimental realization of their intertwined relations has been challenging. Here, we detect chiral kagome superconductivity modulations with residual Fermi arcs in KV3Sb5 and CsV3Sb5 by normal and Josephson scanning tunneling microscopy down to 30mK with resolved electronic energy difference at microelectronvolt level. We observe a U-shaped superconducting gap with flat residual in-gap states. This gap exhibits chiral 2 by 2 spatial modulations with magnetic field tunable chirality, which align with the chiral 2 by 2 pair density modulations observed through Josephson tunneling. These findings demonstrate a chiral pair density wave (PDW) that breaks time-reversal symmetry. Quasiparticle interference imaging of the in-gap zero-energy states reveals segmented arcs, with high-temperature data linking them to parts of the reconstructed V d-orbital states within the charge order. The detected residual Fermi arcs can be explained by the partial suppression of these d-orbital states through an interorbital 2 by 2 PDW and thus serve as candidate Bogoliubov Fermi states. Additionally, we differentiate the observed PDW order from impurity-induced gap modulations. Our observations not only uncover a chiral PDW order with orbital-selectivity, but also illuminate the fundamental space-momentum correspondence inherent in finite momentum paired superconductivity.