Discovery of unconventional chiral charge order in kagome superconductor KV3Sb5

TL;DR

This study uncovers an unconventional chiral charge order in the kagome superconductor KV3Sb5, revealing a topological band structure, charge density wave features, and potential links to anomalous Hall effects and superconductivity.

Contribution

It provides the first experimental evidence of a chiral charge density wave in a kagome superconductor, combining STM imaging with theoretical analysis.

Findings

Observation of a 2x2 charge superlattice in KV3Sb5

Detection of an energy gap at the Fermi level with charge modulation reversal

Identification of chiral anisotropy and magnetic field response in charge order

Abstract

Intertwining quantum order and nontrivial topology is at the frontier of condensed matter physics. A charge density wave (CDW) like order with orbital currents has been proposed as a powerful resource for achieving the quantum anomalous Hall effect in topological materials and for the hidden phase in cuprate high-temperature superconductors. However, the experimental realization of such an order is challenging. Here we use high-resolution scanning tunnelling microscopy (STM) to discover an unconventional charge order in a kagome material KV3Sb5, with both a topological band structure and a superconducting ground state. Through both topography and spectroscopic imaging, we observe a robust 2x2 superlattice. Spectroscopically, an energy gap opens at the Fermi level, across which the 2x2 charge modulation exhibits an intensity reversal in real-space, signaling charge ordering. At impurity-pinning free region, the strength of intrinsic charge modulations further exhibits chiral anisotropy with unusual magnetic field response. Theoretical analysis of our experiments suggests a tantalizing unconventional chiral CDW in the frustrated kagome lattice, which can not only lead to large anomalous Hall effect with orbital magnetism, but also be a precursor of unconventional superconductivity.