▎ 摘　　要

Using a nonperturbative functional renormalization group approach, we calculate the renormalized quasi-particle velocity v(k) and the static dielectric function epsilon(k) of suspended graphene as functions of an external momentum k. Our numerical result for v(k) can be fitted by v(k)/v(F) = A + B ln(Lambda(0)/k), where v(F) is the bare Fermi velocity, Lambda(0) is an ultraviolet cutoff, and A = 1.37, B = 0.51 for the physically relevant value (e(2)/v(F) = 2.2) of the coupling constant. In contrast to calculations based on the static random-phase approximation, we find that epsilon(k) approaches unity for k -> 0. Our result for v(k) agrees very well with a recent measurement by Elias et al. [Nat. Phys. 7, 701 (2011)].