  We report on asymmetric electron-hole decoherence in epitaxial graphene gated
by an ionic liquid. The observed negative magnetoresistance near zero magnetic
field for different gate voltages, analyzed in the framework of weak
localization, gives rise to distinct electron-hole decoherence. The hole
decoherence rate increases prominently with decreasing negative gate voltage
while the electron decoherence rate does not exhibit any substantial gate
dependence. Quantitatively, the hole decoherence rate is as large as the
electron decoherence rate by a factor of two. We discuss possible microscopic
origins including spin-exchange scattering consistent with our experimental
observations.
