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TT: Fachverband Tiefe Temperaturen

TT 72: SrTiO₃: A Versatile Material from Bulk Quantum Paraelectric to 2D Superconductor II (joint session TT/KFM/MA/O)

TT 72.3: Talk

Thursday, March 21, 2024, 15:30–15:45, H 0104

Dislocation-based filamentary superconductivity in reduced SrTiO₃ — •Christian Rodenbücher¹, Gustav Bihlmayer², Carsten Korte¹, and Kristof Szot³ — ¹Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research (IEK-14), 52425 Jülich, Germany — ²Forschungszentrum Jülich GmbH, Peter Grünberg Institut (PGI-1), 52425 Jülich, Germany — ³University of Silesia, Institute of Physics, 41-500 Chorzów, Poland

Exposure of SrTiO₃ single crystals to reducing conditions at elevated temperatures leads to the generation of metallic filaments forming along of dislocations, which act as preferential reduction sites. This effect can be enhanced when stimulating the local deoxidation by electric fields. This results in an agglomeration of metallic filaments in nano-bundles, which are embedded in the insulating surrounding crystal matrix. Despite removing only 10¹⁴⁻¹⁵ oxygen atoms from the dislocation network, electro-reduced crystals are superconducting with a transition temperature of 0.2 K, and their residual resistance is lower than that of purely thermally-reduced crystals. As the total amount of oxygen removed during electro-reduction is much smaller than the smallest reported carrier concentration for superconducting SrTiO_3−x so far, our findings challenge traditional explanations of superconductivity in metal oxides. Combining conductivity characterization by atomic force microscopy with theoretical analysis of the dislocation cores, we propose a model explaining the superconducting properties by the coexistence of metallic dislocation cores with polar insulating regions allowing for polaronic coupling in the bundles.

Keywords: strontium titanate; reduction; dislocations; filaments; metallicityc