Orbital-dependent polaron formation in the relativistic Mott insulator Sr sub(2) IrO sub(4)

Authors present optical spectroscopy measurements of 5d transition metal oxide Sr sub(2) IrO sub(4). The results are interpreted in terms of orbital-dependent electron-phonon interaction and are essential for understanding the physics of this material. We use optical spectroscopy to investigate the electron-phonon interaction in Sr sub(2) IrO sub(4), a well-known 5d transition metal oxide with spin-orbit entangled states. The temperature evolution in the optical spectra is well described by the Frohlich polaron model, indicating a large electron-phonon interaction. We further find that electrons in different orbitals selectively couple with different phonon modes. While J sub(eff) = 3/2 holes do not seem to couple with any phonons, J sub(eff) = 1/2 and 3z super(2) - r super(2) electrons mainly couple with in-plane and out-of-plane Ir-O bending modes, respectively. The symmetries of the orbitals and phonons are consistent with our observations.