Sub-GeV dark matter (DM) scattering with electrons can produce a detectable signal in a liquid scintillator. In particular, aromatic compounds such as benzene or xylene have an electronic excitation energy of a few eV, making them sensitive to DM as light as a few MeV. We develop the formalism for DM–electron scattering in aromatic organic molecules, calculate the expected rate in benzene and p-xylene, and apply this calculation to an existing measurement of single photo-electron emission rate in a low-background EJ-301 scintillator cell. Despite the fact that this measurement was performed in a shallow underground laboratory under minimal overburden, the DM–electron scattering limits extracted from these data are already approaching leading constraints in the 3–100 MeV DM mass range. We discuss possible next steps in the evolution of this direct detection technique, in which scalable organic scintillators are used in solid or liquid crystal phases and in conjunction with semiconductor photodetectors to improve sensitivity through directional signal information and potentially lower dark rates per unit mass.
