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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 7: Dielectric, Elastic and Electromechanical Properties

KFM 7.3: Vortrag

Mittwoch, 29. September 2021, 10:30–10:45, H1

Symmetry breaking by 4f-electron ordering in NdGaO₃ — •Lea Forster¹, Katrin Fürsich², Eva Benckiser², Thomas Lottermoser¹, Manfred Fiebig¹, and Mads C. Weber¹ — ¹ETH Zurich, Switzerland — ²MPI Stuttgart, Germany

Despite intense investigations, the low temperature behavior of 4f electrons in neodymium gallate, NdGaO₃, is not fully understood. Several studies suggest that the 4f electrons affect the physical properties of NdGaO₃ at low temperature, and even a potential structural phase transition has been discussed in light of Raman measurements [1]. In this study, we shed light on these anomalies. We applied optical second harmonic generation (SHG), a highly symmetry-sensitive technique. Furthermore, SHG spectroscopy also gives us an insight into the physical origin of the anomalies. We reveal a strong SHG signal of NdGaO₃ characterized by many spectrally sharp features with increasing intensity toward low temperatures. While the spectral signature identifies the features as 4f transitions, our symmetry analysis reveals a lower symmetry with respect to the expected Pbnm phase of NdGaO₃. We therefore conclude that an orbital ordering of the 4f electrons gives rise to a symmetry breaking in NdGaO₃. This result raises the question whether a similar effect could also appear in other rare-earth compounds.

[1] B. K. De et al., PRB 103, 054106 (2021).