  Owing to its inherent non-trivial geometry, the unique structural motif of
the recently discovered Kagome topological superconductor AV3Sb5 is an ideal
host of diverse topologically non-trivial phenomena, including giant anomalous
Hall conductivity, topological charge order, charge density wave, and
unconventional superconductivity. Despite possessing a normal-state CDW order
in the form of topological chiral charge order and diverse superconducting gaps
structures, it remains unclear how fundamental atomic-level properties and
many-body effects including Fermi surface nesting, electron-phonon coupling,
and orbital hybridization contribute to these symmetry-breaking phenomena.
Here, we report the direct participation of the V3d-Sb5p orbital hybridization
in mediating the CDW phase transition in CsV3Sb5. The combination of
temperature-dependent X-ray absorption and first principles studies clearly
indicate the Inverse Star of David structure as the preferred reconstruction in
the low-temperature CDW phase. Our results highlight the critical role that Sb
orbitals plays and establish orbital hybridization as the direct mediator of
the CDW states and structural transition dynamics in Kagome unconventional
superconductors. This is a significant step towards the fundamental
understanding and control of the emerging correlated phases from the Kagome
lattice through the orbital interactions and provide promising approaches to
novel regimes in unconventional orders and topology.
