High-pressure investigation of magnon excitation in bilayer square lattice iridate Sr₃Ir₂O₇ through resonant inelastic x-ray scattering

Bilayer square lattice iridate, Sr₃Ir₂O₇, is considered as a promising platform to realize novel phases such as valence bond solids, Bose glass, quantum dimer phase under small perturbations like external pressure, since it has a small charge gap, proximity to the Mott transition and comparable interlayer and intralayer exchange interactions. The high-pressure Raman study of Sr₃Ir₂O₇ found an interesting magnetic transition that concurs with a structural transition around 14.4 GPa. Although resonant inelastic X-ray scattering (RIXS) is a great tool to characterize this quantum magnetic transition, RIXS experiments with high-pressure setup has been challenging due to the extrinsic signals from sample environment. Here, we investigate the magnon excitation of Sr₃Ir₂O₇ under high pressure, using a newly developed resonant inelastic x-ray scattering spectrometer for high-pressure studies [1]. At low pressure below 11GPa, a well-defined magnon is observed. At higher pressures, the magnon excitation exhibits both hardening and broadening. Magnon becomes highly damped at the phase boundary between antiferromagnetic (AFM) and high-pressure paramagnetic phase. The high-pressure paramagnetic phase is further studied using the high field x-ray magnetic circular dichroism (XMCD).

[1] Jin-Kwang Kim, Jungho Kim et al., J. Synchrotron Rad. 27, 963-969 (2020).