Speaker: Prof Igor Herbut
Affiliation: Simon Fraser University, Canada
Abstract Details: I will review recent progress in our understanding of strongly interacting electronic systems that have their Fermi surfaces reduced to points. The first example will involve the familiar Dirac electrons in two dimensions described by the Hubbard, or a Hubbard-like, model. Recent confluence of field-theoretic and numerical methods leads a rather detailed and quantitative picture of metal-insulator quantum phase transition in this system, at which sharp quasiparticles disappear and Mott gap and Neel order parameter simultaneously emerge at a critical interaction strength. A connection to the observed quantum Hall effect at the neutrality point in graphene under magnetic field will be noted. The second example will go beyond Dirac 'relativistic' dispersion, and concern the effect of Coulomb interactions in systems such as gray tin or mercury telluride, where due to strong spin-orbit coupling and the ensuing band inversion electronic bands touch quadratically at the Fermi level.  We will examine the stability of the putative non-Fermi liquid ground state proposed by Abrikosov and Beneslavskii in the 70's, and discuss a general mechanism for an instability of such scale-invariant interacting phases.

About The Speaker: Igor Herbut is Full Professor at the Department of Physics, Simon Fraser University (Canada). He is well know for his contributions to quantum condensed matter theory and mathematical physics, in particular, in the applications of field and gauge theories to quantum phase transitions, strong correlations, disordered systems, superconductivity, Dirac fermions, graphene physics, supersymmetry, index theorems, and topology. He is single author of one book and ~35 research papers, and co-author of another ~65. These include 21 papers in Physical Review Letters and 2 in Physical Review X. Igor is ranked within the top 0.75% of the most influential authors of APS publications in 2006 according to SARA (www.physauthorsrank.org)

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