Fig. 2: Expected electronic steady-state distribution.

a Key scattering processes between the graphene K and K’ valleys facilitated by photons (arrow 1), surface acoustic phonons (arrows 2,3), and graphene acoustic phonons (arrow 4) that contribute to the steady state. b Steady state distribution (black solid curve) for \(P=\,\)1.9 mW/μm² and equilibrium distribution (blue dashed curve) of electrons at doping \({{{\rm{E}}}}_{{{\rm{F}}}}=0\), where the longitudinal photoconductivity is enhanced relative to equilibrium. Here, \(\varepsilon\) denotes the quasienergy and \({{{\rm{F}}}}_{{{\bf{k}}}\alpha }\) denotes the electronic occupation. c Steady state distribution (black solid curve) of electrons at doping \({{{\rm{E}}}}_{{{\rm{F}}}}=0.35\,\hslash \varOmega\) and \(P=\) 0.8 mW/µm², where the photoconductivity is suppressed relative to an equilibrium distribution expectation (blue dashed curve). d Same as (c) but for a larger power density \({P}=\,\)1.9 mW/µm², where the steady state distribution exhibits additional electron density above the Floquet gap. e Steady state distribution (black solid curve) of electrons for \(P=\,\)1.9 mW/µm² at doping \({{{\rm{E}}}}_{{{\rm{F}}}}=0.75\,\hslash \varOmega\), where the photoconductivity is approximately identical to that of an equilibrium distribution (blue dashed curve), with a slightly raised effective temperature due to multi-photon heating processes. The horizontal dotted lines in (b–e) mark\(\,\varepsilon\) values corresponding to \(\pm 1/2\hslash \varOmega\).