▎ 摘　　要

We show that the onset of soft parametric resonance (SPR) at omega = eta omega(F), where omega(F) = eF(o)v(f)/(h) over bar omega(OP) for hot carriers interacting with optic phonons (h) over bar omega(OP) in graphene is independent of temperature, whereas eta similar to 0.56 is practically independent of the DC field F-o, which makes SPR tunable over a sizeable range of F-o. Our model based on the linearization of the time-dependent Boltzmann transport equation (BTE) predicts a secondary resonance at omega similar to omega(F), emerging from a weak shoulder in the ac current at T = 300 K, when the temperature decreases to T = 77 K and lower. The two resonances behave differently as scattering at low energy strengthens. (C) 2013 AIP Publishing LLC.