  Excitons are two-particle correlated bound states that are formed due to
Coulomb interaction between single-particle holes and electrons. In the
solid-state, cooperative interactions with surrounding quasiparticles can
strongly tailor the exciton properties and potentially even create new
correlated states of matter. It is thus highly desirable to access such
cooperative and correlated exciton behavior on a fundamental level. Here, we
find that the ultrafast transfer of an exciton's hole across a type-II
band-aligned moir\'e heterostructure leads to a surprising sub-200-fs upshift
of the single-particle energy of the electron being photoemitted from the
two-particle exciton state. While energy relaxation usually leads to an
energetic downshift of the spectroscopic signature, we show that this unusual
upshift is a clear fingerprint of the correlated interactions of the electron
and hole parts of the exciton quasiparticle. In this way, time-resolved
photoelectron spectroscopy is straightforwardly established as a powerful
method to access exciton correlations and cooperative behavior in
two-dimensional quantum materials. Our work highlights this new capability and
motivates the future study of optically inaccessible correlated excitonic and
electronic states in moir\'e heterostructures.
