Regensburg 2022 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 10: Focus session: Polar Materials Meet Energy demands

KFM 10.2: Hauptvortrag

Dienstag, 6. September 2022, 10:00–10:30, H5

Negative capacitance and voltage amplification in ferroelectric heterostructures — •Jorge Iniguez — Luxembourg Institute of Science and technology — University of Luxembourg

My group is interested in the behavior of ferroelectric materials that present non-trivial polar orders (vortexes, skyrmions) and properties (chirality, negative capacitance) in situations of reduced dimensionality (ultra-thin layers or films) and/or subject to suitable electrostatic boundary conditions. In this talk I will review our most recent theoretical results for one of the model systems in the field, the PbTiO₃/SrTiO₃ ferroelectric/dielectric superlattices where many of the above effects were first demonstrated. In particular, I will discuss the negative-capacitance response of such materials, with an emphasis on the attendant voltage amplification. I will show that this anomalous behavior is actually quite frequent, occurring in regular multi-domain structures as well as in novel topological states. Further, I will explain its atomistic underpinnings and show how it can be optimized (to obtain voltage amplifications beyond x10) if the polar layers are tuned to display an incipient ferroelectric state.

Most of the work done in collaboration with M. Graf and H. Aramberri (postdocs at the Luxembourg Institute of Science and Technolgoy) and funded by the Luxembourg National Research Fund through Grants INTER/RCUK/18/12601980 and C18/MS/12705883/REFOX. Other key contributors include P. Zubko (UC London), J. Junquera (U. Cantabria), R. Ramesh (UC Berkeley), etc.