Discovery of conjoined charge density waves in the kagome superconductor CsV3Sb5

Abstract

The electronic instabilities in CsV3Sb5 are believed to originate from the V 3d-electrons on the kagome plane, however the role of Sb 5p-electrons for 3-dimensional orders is largely unexplored. Here, using resonant tender X-ray scattering and high-pressure X-ray scattering, we report a rare realization of conjoined charge density waves (CDWs) in CsV3Sb5, where a 2 x 2 x 1 CDW in the kagome sublattice and a Sb 5p-electron assisted 2 x 2 x 2 CDW coexist. At ambient pressure, we discover a resonant enhancement on Sb L-1-edge (2s -> 5p) at the 2 x 2 x 2 CDW wavevectors. The resonance, however, is absent at the 2 x 2 x 1 CDW wavevectors. Applying hydrostatic pressure, CDW transition temperatures are separated, where the 2 x 2 x 2 CDW emerges 4 K above the 2 x 2 x 1 CDW at 1 GPa. These observations demonstrate that symmetry-breaking phases in CsV3Sb5 go beyond the minimal framework of kagome electronic bands near van Hove filling. The nature of unconventional charge density wave in kagome metals is currently under intense debate. Here the authors report the coexistence of the 2 x 2 x 1 charge density wave in the kagome sublattice and the Sb 5p-electron assisted 2 x 2 x 2 charge density waves in CsV3Sb5.