Honeycomb-lattice quantum magnets with strong spin-orbit coupling are promising candidates for realizing a Kitaev quantum spin liquid. Although iridate materials such as Li2IrO3 and Na2IrO3 have been extensively investigated in this context, there is still considerable debate as to whether a localized relativistic wavefunction (J eff = 1/2) provides a suitable description for the electronic ground state of these materials. To address this question, we have studied the evolution of the structural and electronic properties of α-Li2IrO3 as a function of applied hydrostatic pressure using a combination of X-ray diffraction and X-ray spectroscopy techniques. We observe striking changes even under the application of only small hydrostatic pressure (P ≤ 0.1 GPa): A distortion of the Ir honeycomb lattice (via X-ray diffraction), a dramatic decrease in the strength of spin-orbit coupling effects (via X-ray absorption spectroscopy), and a significant increase in non-cubic crystal electric field splitting (via resonant inelastic X-ray scattering). Our data indicate that α-Li2IrO3 is best described by a J eff = 1/2 state at ambient pressure, but demonstrate that this state is extremely fragile and collapses under the influence of applied pressure.
Bibliographical noteFunding Information:
Work at the University of Toronto was supported by the Natural Science and Engineering Research Council (NSERC) of Canada through the Collaborative Research and Training Experience (CREATE) program (432242-2013) and a Discovery Grant (RGPIN-2014-06071). Y.S. acknowledges DST, India for support through DST Grant No. SB/S2/CMP-001/2013. S. D. acknowledges support from NSERC. K.M. acknowledges UGC-CSIR India for a fellowship. G. R. acknowledges Israeli Science Foundation Grant #1189/14. Y.D is supported by NSFC Grant No. U1530402, National Key R & D Program of China 2018YFA0305703 and the Science Challenge Project, No. TZ2016001. Y.L. thanks the support by the National Research Foundation of Korea (NRF) grant (No. 2018R1A3B1052042) funded by the Korea government (MSIP). Research described in this paper was performed at the Canadian Light Source, which is supported by the Canada Foundation for Innovation, the Natural Sciences and Engineering Research Council of Canada, the University of Saskatchewan, the Government of Saskatchewan, Western Economic Diversification Canada, the National Research Council Canada, and the Canadian Institutes of Health Research. In addition, this research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
© 2018 The Author(s).
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics