Quantum Cafe: Mikhail Katsnelson

Quantum Café is CCQ’s ongoing seminar series: open to all bona fide members of the greater NYC scientific community and held every second week, Quantum Café presents a series of informal, highly interactive talks, typically by external speakers, which present the most interesting recent developments and open questions in our field.

Title: Many-Body Effects in Graphene

Abstract: A huge recent progress in the sample quality makes many-body effects in electron spectrum of graphene near neutrality point observable. Model approaches for the Dirac electrons with Coulomb interaction were intensively developed in the last ten years. I am going to focus, rather, on materials-science aspects of the problem, including first-principles calculations of effective Coulomb interaction and its further mapping on the optimal Hubbard model; I will discuss also a problem of spelectron magnetismin graphene and other graphitic systems.

I will present the results of Quantum Monte Carlo simulations for pristine and defected graphene. They demonstrate a crucial importance of realistic interelectron interaction potential for the phase diagram of isolated graphene and give the final answer in a long and controversial discussion on many-body renormalization of optical conductivity in graphene. It turns out that this renormalization is very weak or absent. As an example of unusual many-body effects in graphene I will discuss also the renormalization of ballistic minimal conductivity by the electron-electron Coulomb interaction.