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

TL;DR

This study uses high-pressure NMR to investigate the magnetic properties of $eta$-Li$_2$IrO$_3$, revealing a suppression of local susceptibility and signs of a quantum spin liquid-like state under pressure.

Contribution

First high-pressure NMR analysis of $eta$-Li$_2$IrO$_3$ showing suppression of susceptibility and evidence for an exotic quantum spin liquid-like ground state.

Findings

Structural phase transition around 200 K

Suppressed local magnetic susceptibility at high pressure

Power-law temperature dependence of spin-lattice relaxation

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.