Collapse of susceptibility and non-trivial spin dynamics in the hyper-honeycomb magnet $\beta$-Li${}_2$IrO${}_3$ under high pressure

Abstract

We present high-pressure (2 GPa) ${}^7$Li nuclear magnetic resonance (NMR) measurements on single crystals of the hyper-honeycomb Kitaev magnet $\beta$-Li${}_2$IrO${}_3$. The spectra show evidence for a structural phase transition around 200 K and a coexistence of phases, consistent with the results of other measurement techniques. The NMR spectra and line shift measurements demonstrate a strong suppression of the local magnetic susceptibility at high pressure. However, the spin-lattice relaxation ($1/T_1$) shows a clear power-law temperature dependence. This is inconsistent with a gapped singlet ground state of dimers and tetramers, as was previously proposed, and is instead evocative of a more exotic quantum spin liquid-like ground state.

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