Publications associated with Quantum Magnetism and Quantum Phase Transitions

Spin waves and revised crystal structure of honeycomb iridate Na2IrO3

Physical Review Letters 108 (2012) 127204

SK Choi, R Coldea, AN Kolmogorov, T Lancaster, II Mazin, SJ Blundell, PG Radaelli, Y Singh, P Gegenwart, KR Choi, S-W Cheong, PJ Baker, C Stock, J Taylor

We report inelastic neutron scattering measurements on Na2IrO3, a candidate for the Kitaev spin model on the honeycomb lattice. We observe spin-wave excitations below 5 meV with a dispersion that can be accounted for by including substantial further-neighbor exchanges that stabilize zig-zag magnetic order. The onset of long-range magnetic order below 15.3 K is confirmed via the observation of oscillations in zero-field muon-spin rotation experiments. Combining single-crystal diffraction and density functional calculations we propose a revised crystal structure model with significant departures from the ideal 90 deg Ir-O-Ir bonds required for dominant Kitaev exchange.

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