Universal conductivity in graphene with short-range

by Alessandro Giuliani

Friday 25 Mar 2011, 16:00 → 18:00 Europe/Rome

Aula Careri (Dipartimento di Fisica - Ed. G.Marconi)

Review recent results on the ground state properties of the 2D Hubbard model on the honeycomb lattice, a natural model for interacting electrons on a single graphene sheet. At half-filling and weak coupling, we construct the ground state correlation functions in terms of a convergent resummed expansion. In particular, the conductivity (at imaginary frequency) is analytic in the strength of the electron-electron interaction, for all non zero frequencies. More: in the zero frequency limit, conductivity approaches a universal value, independent of lattice spacing, of the hopping strength and, remarkably, of electron-electron interaction strength. The result, one of the very few universality examples in condensed matter established on firm mathematical grounds, is based on a combination of constructive Renormalization Group methods with exact lattice Ward identities. Time permitting, I will comment about order by order results on the case of graphene with electromagnetic interactions. (Joint with V. Mastropietro and M. Porta).