We use optical spectroscopy to investigate the electron-phonon interaction in Sr2IrO4, a well-known 5d transition metal oxide with spin-orbit entangled states. The temperature evolution in the optical spectra is well described by the Fröhlich polaron model, indicating a large electron-phonon interaction. We further find that electrons in different orbitals selectively couple with different phonon modes. While Jeff = 3/2 holes do not seem to couple with any phonons, Jeff = 1/2 and 3z2−r2 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.
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This work was supported by the Research Center Program of the Institute for Basic Science in Korea. S.J.M. was supported by Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning (2012R1A1A1013274) and TJ Park Science Fellowship of POSCO TJ Park Foundation.
Sohn, C. H.; Lee, Min-Cheol; Park, H. J.; Noh, Kyung Joo; Yoo, H. K.; Moon, S. J.; Kim, K. W.; Qi, T. F.; Cao, Gang; Cho, Deok-Yong; and Noh, T. W., "Orbital-Dependent Polaron Formation in the Relativistic Mott Insulator Sr2IrO4" (2014). Physics and Astronomy Faculty Publications. 302.