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Novel Phases in Mott-insulating iridates

In this talk we will present results of our studies on two families of iridates. The honey-comb lattice iridates A2IrO3 (A = Na, Li)  and the hyper-kagome material Na4Ir3O8.  The A2IrO3 materials are novel spin-orbit driven Mott-insulators which  show magnetic behaviors that are consistent with the Kitaev-Heisenberg model with the Li system situated closer to the Kitaev limit.  We also present first results on trying to tune these materials to interesting phases like topological insulator or unconventional superconductivity.  The Na4Ir3O8 system is a highly frustrated magnet and a possible candidate for a quantum spin-liquid. We present low temperature (T ~ 75 mK) thermodynamic measurements of the heat capacity and thermal conductivity to explore the possibility of gapless spinon excitations. We also present magneto-caloric effect measurements to explore the proximity to a quantum critical point.