Tuning the electronic and thermoelectric response of oxide superlattices by confinement, strain and interface polarity*

Transition metal oxides are prospective candidates for energy conversion applications e.g. as thermoelectrics owing to their chemical and thermal stability and in particular to their complex correlated nature. Nanostructuring and reduced dimensionality can lead to further performance enhancement. By combining DFT+U calculations and Boltzmann transport theory we explore the implications of interface polarity, confinement and strain on the thermoelectric properties of perovskite superlattices. Taking as an example LaNiO₃/SrTiO₃(001), we demonstrate that compatible n- and p-type materials can be realized by selective choice of the layer stacking at polar interfaces [1]. On the other hand, a strongly enhanced thermoelectric response is obtained in nonpolar LaNiO₃/LaAlO₃(001) superlattices due to the confinement-driven metal-to-insulator transition [2]. This concept is further extended to (SrXO₃)₁/(SrTiO₃)_n(001) SL with X = V, Cr, and Mn [3]. Last but not least, the thermoelectric response of topologically nontrivial phases is discussed.
[1] B. Geisler, A. Blanca-Romero and R. Pentcheva, Phys. Rev. B 95, 125301 (2017); patent pending
[2] B. Geisler and R. Pentcheva, Phys. Rev. Materials 2, 055403 (2018); PR Applied 11, 044047 (2019).
[3] M. Verma, B. Geisler, and R. Pentcheva, Phys. Rev. B 100, 165126 (2019).