  Fullerenes have unique physical and chemical properties that are associated
with their delocalized conjugated electronic structure. Among them, there is a
giant ultra-broadband - and therefore ultrafast - plasmon resonance, which for
C$_{60}$ is in the extreme-ultraviolet energy range. While this peculiar
resonance has attracted considerable interest for the potential downscaling of
nanoplasmonic applications such as sensing, drug delivery and photocatalysis at
the atomic level, its electronic character has remained elusive. The ultrafast
decay time of this collective excitation demands attosecond techniques for
real-time access to the photoinduced dynamics. Here, we uncover the role of
electron correlations in the giant plasmon resonance of C$_{60}$ by employing
attosecond photoemission chronoscopy. We find a characteristic photoemission
delay of up to 200 attoseconds pertaining to the plasmon that is purely induced
by coherent large-scale correlations. This result provides novel insight into
the quantum nature of plasmonic resonances, and sets a benchmark for advancing
nanoplasmonic applications.
