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arXiv · 2101.07522

Lattice dynamics and structural transition of the hyperhoneycomb iridate $\beta$-Li$_2$IrO$_3$ investigated by high-pressure Raman scattering

Sungkyun Choi·Heung-Sik Kim·Hun-Ho Kim·Aleksandra Krajewska·Gideok Kim·Matteo Minola·Tomohiro Takayama·Hidenori Takagi·Kristjan Haule·David Vanderbilt·Bernhard Keimer
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Abstract

We report a polarized Raman scattering study of the lattice dynamics of $\beta$-Li$_2$IrO$_3$ under hydrostatic pressures up to 7.62 GPa. At ambient pressure, $\beta$-Li$_2$IrO$_3$ exhibits the hyperhoneycomb crystal structure and a magnetically ordered state of spin-orbit entangled Jeff = 1/2 moments that is strongly influenced by bond-directional (Kitaev) exchange interactions. At a critical pressure of ~ 4.1 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 $\beta$-Li$_2$IrO$_3$ to the pressure-induced structural transition.

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Sungkyun Choi, Heung-Sik Kim, Hun-Ho Kim, Aleksandra Krajewska, Gideok Kim, Matteo Minola, Tomohiro Takayama, Hidenori Takagi, Kristjan Haule, David Vanderbilt, Bernhard Keimer. 2021-01-19. Lattice dynamics and structural transition of the hyperhoneycomb iridate $\beta$-Li$_2$IrO$_3$ investigated by high-pressure Raman scattering. https://doi.org/10.1103/physrevb.101.054102

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