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 TN ∼ 240 K. The strongest effect is detected for the A1g mode at 272 cm−1 associated with the modulation of the Ir–O–Ir bond angle. Additionally, the A1g mode at 560 cm−1 shows a Fano asymmetric lineshape sensitive to TN, supporting the existence of low energy (∼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.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 TN ∼ 240 K. The strongest effect is detected for the A1g mode at 272 cm−1 associated with the modulation of the Ir–O–Ir bond angle. Additionally, the A1g mode at 560 cm−1 shows a Fano asymmetric lineshape sensitive to TN, supporting the existence of low energy (∼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.