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arXiv · 2512.05664

Improving 2D-ness to enhance thermopower in oxide superlattices

Dongwon Shin·Inseo Kim·Min-Su Kim·Yu-Qiao Zhang·Woo Tack Lim·Si-Young Choi·Minseok Choi·Hiromichi Ohta·Woo Seok Choi
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Abstract

The transport dynamics of itinerant charge carriers and their interactions with the environment. For two-dimensional oxide thermoelectrics, predominantly represented by doped SrTiO3-based superlattices, reduced spatial dimensions and increased effective mass are known to enhance thermopower (S). However, because of their large effective Bohr radius resulting from their high dielectric constant, SrTiO3-based systems have limitations in exhibiting the 2D characteristic. Here, we focus on EuTiO3 as an alternative perovskite platform in which fractional LaxEu1-xTiO3/EuTiO3 artificial superlattices demonstrate the improvement in 2D nature for the dimensionality-induced improvement of S. We observed a quasi-2D thermopower S2D of -950 uV K-1 and S2D/S3D of ~20 resulting from the improved 2D confinement. Thermopower measurements, combined with hybrid density functional theory calculations, show the enhanced S originates from the confinement of Ti 3dxy-states within the LaxEu1-xTiO3 layers and the associated increase in the 2D density of states. In detail, a smaller effective Bohr radius and modified electronic band structures, in conjunction with the presence of the Eu 4f-states in EuTiO3 which modified the local electronic potential and strengthened the spatial confinement of Ti 3d-states. This approach to improving the dimensional confinement establishes a small effective Bohr radius and Eu 4f-state assisted 2D confinement provides valuable insights into the design of high-performance applications in artificial oxide superlattices.

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Dongwon Shin, Inseo Kim, Min-Su Kim, Yu-Qiao Zhang, Woo Tack Lim, Si-Young Choi, Minseok Choi, Hiromichi Ohta, Woo Seok Choi. 2025-12-05. Improving 2D-ness to enhance thermopower in oxide superlattices. https://doi.org/10.1088/1361-6633%2Fae2f96.

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