Novel 'deconfined' criticality in quantum magnets Leon Balents, Professor of Physics, University of California, Santa Barbara

Among Landau's many significant contributions to physics are his theory of phase transitions (the "Landau rules" and Landau-Ginzburg-Wilson formulation), which underlies most of the critical phenomena revolution, and his Fermi liquid theory, the basis for our understanding of metals and the solid state.  I will describe recent theoretical progress in understanding quantum phase transitions in frustrated magnets, which unveils violations of both paradigms.  The critical theory is not expressed in terms of the order parameters characterizing either state but involves fractionalized degrees of freedom and an emergent, topological, global conservation law.  It is most naturally described as a U(1) gauge theory.  I will comment on the broader implications of our results for the study of quantum criticality in correlated electron systems.