Magnetic excitations and interactions in the Kitaev hyperhoneycomb iridate β-Li2IrO3

Thomas Halloran, Yishu Wang, Mengqun Li, Ioannis Rousochatzakis, Prashant Chauhan, M. B. Stone, Tomohiro Takayama, Hidenori Takagi, N. P. Armitage, Natalia B. Perkins, Collin Broholm

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Abstract

We present a thorough experimental study of the three-dimensional hyperhoneycomb Kitaev magnet β-Li2IrO3, using a combination of inelastic neutron scattering (INS), time-domain terahertz spectroscopy (TDTS), and heat capacity measurements. The main results include a massive low-temperature reorganization of the INS spectral weight that evolves into a broad peak centered around 12 meV, and a distinctive peak in the terahertz data at 2.8(1) meV. A detailed comparison to powder-averaged spin-wave theory calculations reveals that the positions of these two features are controlled by the anisotropic Γ coupling and the Heisenberg exchange J, respectively. The refined microscopic spin model places β-Li2IrO3 in close proximity to the Kitaev spin liquid phase.

Original languageEnglish
Article number064423
JournalPhysical Review B
Volume106
Issue number6
DOIs
StatePublished - Aug 1 2022

Funding

This work was supported as part of the Institute for Quantum Matter, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award No. DE-SC0019331. C.B. was supported by the Gordon and Betty Moore foundation EPIQS program under Grant No. GBMF9456. The research at the ORNL Spallation Neutron Source was sponsored by the U.S. Department of Energy, Office of Basic Energy Sciences. We would also like to acknowledge the help of Sayak Dasgupta for heat capacity calculations. N.B.P. and M.L. were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award No. DE-SC0018056. I.R. was supported by the Engineering and Physical Sciences Research Council (Grant No. EP/V038281/1). A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.

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