▎ 摘　　要

We show that hot carriers scattered by optic phonons in graphene undergo an anomalous parametric resonance when modulated by an ac field, at about half of the frequency omega(F) = 2 pi eF upsilon(f) /(h) over bar omega(op), corresponding to ballistic acceleration up to the phonon energy omega(F) = 2 pi eF upsilon(f) /(h) over bar omega(op) in the presence of a dc field F. The resonance occurs in the terahertz range and is tunable with dc electric fields. Dephasing between the current and the ac field also exhibits a nonzero minimum at resonance for weak elastic scattering, while increasing monotonously with ac frequency for strong elastic scattering. The overall effect would also manifest in a long-range spatially varying periodic potential. DOI: 10.1103/PhysRevB.87.155424