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DS: Fachverband Dünne Schichten
DS 23: Frontiers in Electronic-Structure Theory - Focus on Electron-Phonon Interactions III (joint session O/CPP/DS/HL)
DS 23.4: Vortrag
Mittwoch, 18. März 2020, 11:30–11:45, GER 38
Intrinsic polarons on polar surfaces — •Michele Reticcioli1,2, Zhichang Wang2, Igor Sokolovic2, Michael Schmid2, Ulrike Diebold2, Martin Setvin2, and Cesare Franchini2,3 — 1University of Vienna, Center for Computational Materials Science, Vienna, Austria — 2Institute of Applied Physics, Technische Universitaet Wien, Vienna, Austria — 3University of Bologna, Department of Physics and Astronomy, Bologna, Italy
Uncompensated charge at the surface boundary of polar materials is conventionally expected to form a two dimensional electron gas (2DEG), as a result of the alternating charged-plane stacking in the ionic crystals, interrupted by the surface cut. By means of density-functional theory calculations and surface-sensitive experiments, we propose a different paradigm able to accommodate the uncompensated charge in a more effective way, establishing a more favorable ground state for the system, that is the polaron formation (local lattice distortions coupled with charge localization). In fact, the intrinsic uncompensated charge tends to spontaneously localize and form polarons, rather than a 2DEG. Only beyond the critical polaron density, excess charge arising from external doping or defects starts to build dispersed electronic states. Here, we show how polarons and 2DEG compete on the polar KTaO3(001) surface.