▎ 摘　　要

We show that a slight asymmetry in the wave function of graphene can result in a significant enhancement of the nonlinear effect on the optical response. The third-order nonlinear current due to asymmetry modification of the wave function increases with k(F)a, where k(F) is the Fermi eigenvector and a is the lattice constant. The effect of asymmetry can significantly enhance the third-order current at low temperature and at large Fermi energies. For k(F)a around 1, the nonlinear current increases by around 40% at low temperatures. Copyright (C) EPLA, 2014