  Kagome superconductor CsV3Sb5, which exhibits intertwined unconventional
charge density wave (CDW) and superconductivity, has garnered significant
attention recently. Despite extensive static studies, the nature of these
exotic electronic orders remains elusive. In this study, we investigate the
non-equilibrium electronic structure of CsV3Sb5 via time- and angle-resolved
photoemission spectroscopy. Our results reveal that upon laser excitation, the
van Hove singularities immediately shift towards the Fermi level and
subsequently oscillate in sync with a 1.3 THz coherent phonon mode. By
analyzing the coherent intensity oscillations in the energy-momentum (E-k) map,
we find that this coherent phonon is strongly coupled with electronic bands
from both Sb and V orbitals. While typically observable only in the CDW state,
remarkably, we find that the 1.3-THz coherent phonon mode can be persistently
excited at temperatures above T_CDW, suggesting the potential existence of
fluctuated CDW in CsV3Sb5. These findings enhance our understanding of the
unconventional CDW control of kagome superconductivity.
