Isospin-phonon coupling and Fano-interference in spin-orbit Mott insulator Sr2IrO4

The isospin-phonon coupling in Sr2IrO4 is investigated by temperature dependent phonon Raman scattering. Anomalous behavior in the frequency of all studied optical phonons is observed below the magnetic transition temperature T-N similar to 240 K. The strongest effect is detected for the A(1g) mode at 272 cm(-1) associated with the modulation of the Ir-O-Ir bond angle. Additionally, the A(1g) mode at 560 cm(-1) shows a Fano asymmetric lineshape sensitive to T-N, supporting the existence of low energy (similar to 70 meV) electronic excitations that are renormalized by the magnetic order. These results reveal the characteristics of the interaction between the crystal lattice and electronic degrees of freedom in this spin-orbit entangled Mott insulator. Published under license by AIP Publishing.