Topological spin liquid on the hyper-kagome lattice of Na4Ir3O8

Recent experiments on the “hyper-kagome” lattice system Na4Ir3O8 have demonstrated that it is a rare example of a three dimensional spin-1/2 frustrated antiferromagnet. We investigate the role of quantum fluctuations as the primary mechanism lifting the macroscopic degeneracy inherited by classical spins on this lattice. In the semi-classical limit we predict, based on large-N calculations, that an unusual ~q = 0 coplaner magnetically ordered ground state is stabilized with no local “weather vane” modes. This phase melts in the quantum limit and a gapped topological Z2 spin liquid phase emerges. In the vicinity of this quantum phase transition, we study the dynamic spin structure factor and comment on the relevance of our results for future neutron scattering experiments.

Michael J. Lawler,1 Hae-Young Kee,1 Yong Baek Kim,1 and Ashvin Vishwanath2
1Department of Physics, University of Toronto, 60 St. George St., Toronto, Ontario, M5S 1A7, Canada
2Department of Physics, University of California, Berkeley, CA, 94720