Berlin 2018 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 5: Heusler compounds, semimetals and oxides (joint session MA/TT)
MA 5.10: Vortrag
Montag, 12. März 2018, 12:00–12:15, EB 301
Optical properties of pyrochlore iridates: signatures of electron correlation and spin-orbit-lattice coupling — •Alexander Boris1, Alexander Yaresko1, Timofei Larkin1, Ksenia Rabinovich1, Aleksandra Krajewska1,2, Tomohiro Takayama1,2, Hidenori Takagi1,2, and Bernhard Keimer1 — 1Max Planck Institute for Solid State Research, Stuttgart, Germany — 2University of Stuttgart, Stuttgart, Germany
Spectroscopic ellipsometry is used to determine the dielectric function of A2Ir2O7 (A = In,Lu,Y) polycrystalline samples in the wide spectral range from 10 meV to 6.5 eV at temperatures from 7 K to 300 K. Comparing the spectra with the results of relativistic LSDA+U band structure calculations, we quantitatively classify pyrochlore A2Ir2O7 as spin-orbital Jeff=1/2 Mott insulators with the on-site Coulomb interaction U≈ 1.5 eV and electronic bandwidths W=0.3÷0.5 eV. Exciton doublets with pronounced Fano line shapes were identified in Y2Ir2O7 and Lu2Ir2O7 upon cooling below the magnetic ordering temperatures TN= 150 K and 145 K, respectively. Our results indicate considerable effects of long-range Coulomb interaction and spin-orbit-lattice coupling in the 5d pyrochlore compounds and the need for a detailed analysis of their influence on the Jeff=1/2 states. Newly synthesized In2Ir2O7 does not exhibit the absorption edge and phonon anomalies below TN= 45 K and thus serves as a reference.