SKM 2023 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 23: Poster II
MM 23.34: Poster
Dienstag, 28. März 2023, 18:15–20:00, P2/OG1+2
Anharmonicity of the antiferrodistortive soft mode in barium zirconate BaZrO3 — •Petter Rosander1, Erik Fransson1, Cosme Milesi-Brault2,3,4, Constance Toulouse2, Frédéric Bourdarot5, Andrea Piovano5, Alexei Bossak6, Mael Guennou2, and Göran Wahnström1 — 1Chalmers University of Technology, Göteborg, Sweden — 2University of Luxembourg, Belvaux, Luxembourg — 3Luxembourg Institute of Science and Technology, Belvaux, Luxembourg — 4Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic — 5Institut Laue-Langevin, Grenoble, France — 6European Synchrotron Radiation Facility, Grenoble, France
Few perovskites adopt the ideal cubic phase at low temperatures. However, a promising candidate to, on average, remain cubic, even at 0K, is barium zirconate. The competing phase is a structure with sequentially tilted oxygen octahedra. This distortion is driven by the soft tilt mode at the R-point of the cubic Brillouin zone.
We report data from inelastic neutron scattering (INS) on a single crystal of barium zirconate. This reveals that the tilt mode softens substantially from 9.4 meV at room temperature to 5.6 meV at 2K. Additionally, the INS measurement unveils that the acoustic phonon mode at the same point in the Brillouin zone is almost temperature independent, which is in stark contrast to the tilt mode. The theoretical calculations show that it is critical to account for quantum fluctuations in order to correctly reproduce the experimental temperature dependence.