Veiga, LS;
Glazyrin, K;
Fabbris, G;
Dashwood, CD;
Vale, JG;
Park, H;
Etter, M;
... Haskel, D; + view all
(2019)
Pressure-induced structural dimerization in the hyperhoneycomb iridate beta-Li2IrO3 at low temperatures.
Physical Review B
, 100
(6)
10.1103/PhysRevB.100.064104.
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Abstract
A pressure-induced collapse of magnetic ordering in β−Li2IrO3 at Pm∼1.5–2 GPa has previously been interpreted as evidence for possible emergence of spin liquid states in this hyperhoneycomb iridate, raising prospects for experimental realizations of the Kitaev model. Based on structural data obtained at room temperature, this magnetic transition is believed to originate in small lattice perturbations that preserve crystal symmetry, and related changes in bond-directional anisotropic exchange interactions. Here we report on the evolution of the crystal structure of β−Li2IrO3 under pressure at low temperatures (T≤50 K) and show that the suppression of magnetism coincides with a change in lattice symmetry involving Ir-Ir dimerization. The critical pressure for dimerization shifts from 4.4(2) GPa at room temperature to ∼1.5–2 GPa below 50 K. While a direct Fddd→C2/c transition is observed at room temperature, the low temperature transitions involve new as well as coexisting dimerized phases. Further investigation of the Ir (L3/L2) isotropic branching ratio in x-ray absorption spectra indicates that the previously reported departure of the electronic ground state from a Jeff=1/2 state is closely related to the onset of dimerized phases. In essence, our results suggest that the predominant mechanism driving the collapse of magnetism in β−Li2IrO3 is the pressure-induced formation of Ir2 dimers in the hyperhoneycomb network. The results further confirm the instability of the Jeff=1/2 moments and related noncollinear spiral magnetic ordering against formation of dimers in the low-temperature phase of compressed β−Li2IrO3.
| Type: | Article |
|---|---|
| Title: | Pressure-induced structural dimerization in the hyperhoneycomb iridate beta-Li2IrO3 at low temperatures |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1103/PhysRevB.100.064104 |
| Publisher version: | https://doi.org/10.1103/PhysRevB.100.064104 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | Electronic structure, Pressure effects, Structural phase transition, X-ray absorption spectroscopy, X-ray diffraction |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10081028 |
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