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DS: Fachverband Dünne Schichten
DS 18: Optical Analysis of Thin Films (Reflection, Ellipsometry, Raman, IR-DUV Spectroscopy, ...): Session I
DS 18.4: Talk
Wednesday, March 14, 2018, 10:45–11:00, H 0111
Raman spectroscopy study of lattice and electron dynamics in a SrIrO3 film — •Kaushik Sen, Kai Kleindienst, Dirk Fuchs, Karsten Wolf, Rolf Heid, and Matthieu Le Tacon — Institute for Solid State Physics, Karlsruhe Institute of Technology, Karlsruhe, Germany
SrIrO3 has been proposed as a candidate to realize the so-called topological insulator phase due to its strong spin-orbit coupling (0.4 eV) and electron-electron correlations (0.5 eV). The narrow bands and their extreme sensitivity to the rotations of IrO6-octahedra place the compound close to a metal-insulator transition. This has motivated us to investigate the lattice dynamics of these systems, which potentially plays an important role in conductivity. We report the lattice and electron dynamics in a 60 nm thick SrIrO3 film using Raman scattering experiments as a function of temperature and light polarizations. With confocal Raman spectroscopy, we measured the temperature dependence of phonons modes with Ag and B2g symmetries. Corresponding atomic displacements are assigned with the help of first-principle lattice dynamics calculations. Finally, an electronic continuum could directly be evident. We particularly focus our attention on the anomalous temperature dependence of the frequency of the B2g phonon around 390 cm−1 (arises from the rotation of IrO6-octahedra, which is out-of-phase along the direction of c-axis). This indicates an anomalous phonon hardening below 50 K, which deviates from the expected anharmonic phonon decay. It further displays a strong Fano asymmetry attesting the coupling of this mode to the underlying continuum.