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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: Vortrag

Mittwoch, 14. März 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 A_g and B_2g 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 B_2g 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.