Honeycomb iridates such as $\gamma -{\mathrm{Li}}_2{\mathrm{IrO}}_3$ are argued to realize Kitaev spin-anisotropic magnetic exchange, along with Heisenberg and possibly other couplings. While systems with pure Kitaev interactions are candidates to realize a quantum spin-liquid ground state, in $\gamma -{\mathrm{Li}}_2{\mathrm{IrO}}_3$ it has been shown that the presence of competing magnetic interactions leads to an incommensurate spiral spin order at ambient pressure below 38 K. We study the pressure sensitivity of this magnetically ordered state in single crystals of $\gamma -{\mathrm{Li}}_2{\mathrm{IrO}}_3$ using resonant x-ray scattering (RXS) under applied hydrostatic pressures of up to 3 GPa. RXS is a direct probe of electronic order, and we observe the abrupt disappearance of the ${\mathbf{q}}_{\mathrm{sp}}=(0.57,0,0)$ spiral order at a critical pressure $P_c=1.4$ GPa with no accompanying change in the symmetry of the lattice.

• Received 28 February 2017
• Revised 28 May 2017

DOI:https://doi.org/10.1103/PhysRevB.96.020402