Determination of the Mott-Hubbard gap in GdTiO3
Date
2015-08-06
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Publisher
American Physical Society
Abstract
The band gaps of rare-earth titanates are commonly reported to be 0.2–0.7 eV. These values are based on optical
reflectivity measurements, from which the onset of optical absorption is derived. Here we report experimental
and theoretical results on GdTiO3 (GTO) indicating that the gap is significantly larger. Photoluminescence (PL)
measurements show a strong peak near 1.8 eV, consistent with an observed onset in PL excitation (PLE) at about
the same energy. First-principles calculations, based either on density-functional theory (DFT) with a hybrid
functional or on DFT+U, consistently show that the gap is close to 2 eV. We also propose an interpretation
of the previously reported optical absorption spectra. Given the similarities in electronic structure between the
rare-earth titanates, our results for GTO have repercussions for the other members of the series. The results also
affect the design of complex-oxide heterostructures involving these materials.
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Citation
Bjaalie, Lars, et al. "Determination of the Mott-Hubbard gap in GdTiO 3." Physical Review B 92.8 (2015): 085111.