# Pressure-tuning of bond-directional exchange interactions and magnetic frustration in hyperhoneycomb iridate $\beta$-$\mathrm{Li_2IrO_3}$

## TL;DR

This study investigates how applying pressure to hyperhoneycomb iridate $eta$-$ ext{Li}_2 ext{IrO}_3$ alters its electronic and magnetic properties, potentially leading to a quantum spin liquid state through bond-directional exchange interactions.

## Contribution

It reveals pressure-induced electronic reconstruction and anisotropic lattice compression that modify exchange interactions, offering insights into realizing quantum spin liquids in iridates.

## Key findings

- Electronic ground state reconstructs below 2 GPa.
- Magnetic order appears to collapse at low pressure.
- Anisotropic lattice compression influences exchange interactions.

## Abstract

We explore the response of Ir $5d$ orbitals to pressure in $\beta$-$\mathrm{Li_2IrO_3}$, a hyperhoneycomb iridate in proximity to a Kitaev quantum spin liquid (QSL) ground state. X-ray absorption spectroscopy reveals a reconstruction of the electronic ground state below 2 GPa, the same pressure range where x-ray magnetic circular dichroism shows an apparent collapse of magnetic order. The electronic reconstruction, which manifests a reduction in the effective spin-orbit (SO) interaction in $5d$ orbitals, pushes $\beta$-$\mathrm{Li_2IrO_3}$ further away from the pure $J_{\rm eff}=1/2$ limit. Although lattice symmetry is preserved across the electronic transition, x-ray diffraction shows a highly anisotropic compression of the hyperhoneycomb lattice which affects the balance of bond-directional Ir-Ir exchange interactions driven by spin-orbit coupling at Ir sites. An enhancement of symmetric anisotropic exchange over Kitaev and Heisenberg exchange interactions seen in theoretical calculations that use precisely this anisotropic Ir-Ir bond compression provides one possible route to realization of a QSL state in this hyperhoneycomb iridate at high pressures.