While plasmons in noble metal nanostructures enable strong light-matter interactions on nanometer length scales, the overabundance of free electrons in these systems inhibits their sensitivity to weak external stimuli. Countering this limitation, doped graphene has recently arisen as an actively-tunable material platform for plasmonics, offering extreme electromagnetic field concentration for the price of significantly fewer electrons [1,2]. Here we investigate transient modulation in the optical response of nanostructured graphene associated with the absorption of individual plasmons. We base our analysis on complementary classical and quantum-mechanical simulations, which reveal that the energy of a single plasmon, absorbed in a small, lightly-doped graphene nanoisland, can sufficiently modify the temperature of its electrons and chemical potential to produce substantial changes in the optical response within sub-picosecond timescales, effectively shifting or damping the original plasmon absorption resonance peak and thereby blockading subsequent excitation of a second plasmon. The thero-optical single-plasmon blockade consist in a viable ultra-low power all-optical switching mechanism for doped graphene nanoislands, while their combination with quantum emitters could yield applications in biological sensing and quantum nano-optics.
 F. J. García de Abajo, ACS Photon. 1, 135 (2014).
 J. D. Cox and F. J. García de Abajo, Optica 5, 429 (2018).