Electron-induced rippling in graphene.

We show that the interaction between flexural phonons, when corrected by the exchange of electron-hole excitations, may drive the graphene sheet into a quantum critical point characterized by the vanishing of the bending rigidity of the membrane. Ripples arise then due to spontaneous symmetry breaking, following a mechanism similar to that responsible for the condensation of the Higgs field in relativistic field theories, and leading to a zero-temperature buckling transition in which the order parameter is given by the square of the gradient of the flexural phonon field.