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Stability of Dirac Liquids against Strong Coulomb Interaction
Nikolay Prokof'ev, University of Massachussets Amherst, USA
29.06.2018 at 09:00
I will start by presenting the Diagrammatic Monte Carlo technique that allows one to address interacting fermion problems by computing high-order Feynman diagrams. In this talk, I will discuss its application to systems with long-range forces and focus on the problem of stability of the Dirac liquid state (in a graphene type system) against strong Coulomb interaction. So far, all attempts to deal with this problem in the field-theoretical framework were limited either to
perturbative or RPA treatments, with diametrically opposite conclusions. Our calculations aim at the approximations-free solution with controlled accuracy by computing vertex corrections from higher-order skeleton diagrams and establishing the renormalization group flow of the effective Coulomb coupling constant. We unambiguously show that with increasing the system size L (up to ln(L) = 40), the coupling constant always flows towards zero; i.e. the two dimensional Dirac
liquid is an asymptotically free T=0 state with divergent Fermi velocity. I will also briefly mention other results for Coulomb systems.
A 450, Theresienstr. 37