Pressure-induced collapse of spin-orbital Mott state in the hyperhoneycomb iridate $\beta$-Li${}_2$IrO${}_3$

Abstract

Hyperhoneycomb iridate $\beta$-Li${}_2$IrO${}_3$ is a three-dimensional analogue of two-dimensional honeycomb iridates, such as $\alpha$-Li${}_2$IrO${}_3$, which recently appeared as another playground for the physics of Kitaev-type spin liquid. $\beta$-Li${}_2$IrO${}_3$ shows a non-collinear spiral ordering of spin-orbital-entangled $J_{\mathrm{eff}}$ = 1/2 moments at low temperature, which is known to be suppressed under a pressure of $\sim$2 GPa. With further increase of pressure, a structural transition is observed at $P_{\mathrm{S}}$ $\sim$ 4 GPa at room temperature. Using the neutron powder diffraction technique, the crystal structure in the high-pressure phase of $\beta$-Li${}_2$IrO${}_3$ above $P_{\mathrm{S}}$ was refined, which indicates the formation of Ir${}_2$ dimers on the zig-zag chains, with the Ir-Ir distance even shorter than that of metallic Ir. We argue that the strong dimerization stabilizes the bonding molecular orbital state comprising the two local $d_{zx}$-orbitals on the Ir-O${}_2$-Ir bond plane, which conflicts with the equal superposition of $d_{xy}$-, $d_{yz}$- and $d_{zx}$- orbitals in the $J_{\mathrm{eff}}$ = 1/2 wave function produced by strong spin-orbit coupling. The results of resonant inelastic x-ray scattering (RIXS) measurements and the electronic structure calculations are fully consistent with the collapse of the $J_{\mathrm{eff}}$ = 1/2 state. A subtle competition of various electronic phases is universal in honeycomb-based Kitaev materials.

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Cited by in corpus (21)

• Kitaev quantum spin liquid - concept and materialization
• Hunting Majorana Fermions in Kitaev Magnets
• Spin-orbit-entangled electronic phases in 4$d$ and 5$d$ transition-metal compounds
• Possible quantum paramagnetism in compressed Sr${}_2$IrO${}_4$
• Kitaev magnetism through the prism of lithium iridate
• Pressure-induced structural dimerization in the hyperhoneycomb iridate $\beta$-Li${}_2$IrO${}_3$ at low temperatures
• Anisotropic temperature-field phase diagram of single-crystalline $\beta$-Li${}_2$IrO${}_3$: magnetization, specific heat, and ${}^7$Li NMR study
• Complex pressure-temperature structural phase diagram of honeycomb iridate Cu${}_2$IrO${}_3$
• Magnon-spinon dichotomy in the Kitaev hyperhoneycomb $\beta$-Li${}_2$IrO${}_3$
• Optical signature of the pressure-induced dimerization in the honeycomb iridate $\alpha$-Li${}_2$IrO${}_3$
• Resonant inelastic x-ray scattering spectra in the hyperhoneycomb iridate $\beta$-Li${}_2$IrO${}_3$: First principles calculations
• Competing spin-orbital singlet states in the 4$d^4$ honeycomb ruthenate Ag${}_3$LiRu${}_2$O${}_6$
• Magnetic Excitations and Interactions in the Kitaev Hyperhoneycomb Iridate $\beta$-Li${}_2$IrO${}_3$
• Interplay of magnetism and dimerization in pressurized Kitaev material $\beta$-Li${}_2$IrO${}_3$
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• Unconventional magnetic field response of the hyperhoneycomb Kitaev magnet $\beta -{\text{Li}}_2{\text{IrO}}_3$
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