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Topological Edges and Defects of the nu=0 Quantized Hall State in Graphene

TYPECondensed Matter Seminar
Speaker:Herb Fertig
Affiliation:Indiana University
Location:Lidow Nathan Rosen (300)

The nu=0 quantized Hall state in graphene is one the unique manifestations of Dirac physics in this material, which distinguishes it from other two dimensional electron gases. Recent experiments strongly suggest that when the Zeeman energy of the electrons is modified relative to their orbital energy scale, the system can be driven through a quantum phase transition.  A natural interpretation of the experiments is that interactions stabilize different groundstates through a quantum Hall version of ferromagnetism.  Excitations around such states can have unusual topologies that are tied to their charges, with consequences for transport properties of the system.  In this talk we will discuss edges and localized excitations – skyrmions and merons – of two states that are likely participating in the quantum phase transition seen in experiment, a canted antiferromagnet and a ferromagnetic state.  The evolution of the edge structure and charged excitations as the transition is crossed will be discussed, and will be shown to reveal a measure of the order present in the system.