Berlin 2012 – scientific programme

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SYTI: Symposium Topological Insulators: Influence of Superconductivity, Magnetism and Extrinsic Spin-Orbit Interaction

SYTI 1: Topological Insulators: Influence of Superconductivity, Magnetism and Extrinsic Spin-Orbit Interaction

SYTI 1.4: Invited Talk

Tuesday, March 27, 2012, 11:00–11:30, H 0105

Weyl Metal States and Surface Fermi Arcs in Iridates — •Sergey Savrasov — University of California, Davis

We investigate[1] novel phases that emerge from the interplay of electron correlations and strong spin-orbit interactions. We focus on describing the topological semimetal, a three-dimensional phase of a magnetic solid, and argue that it may be realized in a class of pyrochlore iridates (such as Y2Ir2O7) based on calculations using the LDA + U method. This state is a three-dimensional analog of graphene with linearly dispersing excitations and provides a condensed-matter realization of Weyl fermions that obeys a two-component Dirac equation. It also exhibits remarkable topological properties manifested by surface states in the form of Fermi arcs, which are impossible to realize in purely two-dimensional band structures. For intermediate correlation strengths, we find this to be the ground state of the pyrochlore iridates, coexisting with noncollinear magnetic order. A narrow window of magnetic *axion* insulator may also be present. An applied magnetic field is found to induce a metallic ground state.

[1] Xiangang Wan, Ari M. Turner, Ashvin Vishwanath, Sergey Savrasov, Physical Review B 83, 205101 (2011)