Unconventional chiral charge order in kagome superconductor KV₃Sb₅

Intertwining quantum order and non-trivial topology is at the frontier of condensed matter physics. A charge-density-wave-like order with orbital currents has been proposed 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 to discover an unconventional chiral 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 2 × 2 superlattice. Spectroscopically, an energy gap opens at the Fermi level, across which the 2 × 2 charge modulation exhibits an intensity reversal in real space, signalling charge ordering. At the 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 charge density wave in the frustrated kagome lattice, which can not only lead to a large anomalous Hall effect with orbital magnetism, but also be a precursor of unconventional superconductivity.Nanyang Technological UniversityNational Research Foundation (NRF)Accepted versionWe thank Q Wang for stimulating discussions. Experimental and theoretical work at Princeton University was supported by the Gordon and Betty Moore Foundation (GBMF4547 and GBMF9461; M.Z.H.). The material characterization is supported by the US Department of Energy under the Basic Energy Sciences programme (grant no. DOE/BES DE-FG-02-05ER46200). S.D.W. and B.R.O. acknowledge support from the University of California Santa Barbara Quantum Foundry, funded by the National Science Foundation (NSF DMR-1906325). Research reported here also made use of shared facilities of the Materials Research Science and Engineering Center (MRSEC) at University of California Santa Barbara (NSF DMR-1720256). B.R.O. also acknowledges support from the California NanoSystems Institute through the Elings fellowship programme. R.T. is funded by the Deutsche Forschungsgemeinschaft (German Research Foundation) through project ID 258499086 – SFB 1170 and through the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter (ct.qmat) project ID 390858490 – EXC 2147. T.N. acknowledges supports from the European Union’s Horizon 2020 research and innovation programme (ERC-StG-Neupert-757867-PARATOP). Work at Boston College was supported by the US Department of Energy, Basic Energy Sciences grant number DE-FG02-99ER45747. T.A.C. was supported by the National Science Foundation Graduate Research Fellowship Program under grant no. DGE-1656466. Research conducted at the Center for High Energy X-ray Sciences is supported by the National Science Foundation under award DMR-1829070. G.C. would like to acknowledge the support of the National Research Foundation, Singapore under its Fellowship Award (NRF-NRFF13-2021-0010) and the Nanyang Assistant Professorship grant from Nanyang Technological University. G.X. was supported by the National Key Research and Development Program of China (2018YFA0307000) and the National Natural Science Foundation of China (11874022)