Abstract
We report a polarized Raman scattering study of the lattice dynamics of under hydrostatic pressures up to 7.62 GPa. At ambient pressure, exhibits the hyperhoneycomb crystal structure and a magnetically ordered state of spin-orbit entangled = 1/2 moments that are strongly influenced by bond-directional (Kitaev) exchange interactions. At a critical pressure of GPa, the phonon spectrum changes abruptly, consistent with the reported structural transition into a monoclinic, dimerized phase. A comparison to the phonon spectra obtained from density-functional calculations shows reasonable overall agreement. The calculations also indicate that the high-pressure phase is a nonmagnetic insulator driven by the formation of Ir–Ir dimer bonds. Our results thus indicate a strong sensitivity of the electronic properties of to the pressure-induced structural transition.
- Received 28 July 2019
- Revised 8 October 2019
- Accepted 23 December 2019
DOI:https://doi.org/10.1103/PhysRevB.101.054102
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