  There exist two families of superradiance phenomena: relying on correlated
emission by an ensemble of atoms or by free electrons. Here we investigate
emission from an ensemble of atoms driven by coherently shaped electrons. This
interaction creates superradiance emerging from both the atoms' and the
electrons' coherence - with emission intensity that scales quadratically in
both the number of atoms and number of electrons. This phenomenon enables
electrons to become novel probes of quantum correlations in matter, with high
temporal and spatial resolution.
