SKM 2023 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 50: Focus Session: Superconducting Nickelates II

TT 50.2: Vortrag

Donnerstag, 30. März 2023, 15:15–15:30, HSZ 03

Insights into the electronic structure of oxygen reduced and doped nickelates from core-level spectroscopy — •Rebecca Pons — Max-Planck Institut für Festkörperforschung, Stuttgart, Germany — Stewart Blusson Quantum Matter Institute, UBC Vancouver, Canada

With the observation of superconductivity in Sr-doped infinite-layer nickelate Nd_0.8Sr_0.2NiO₂ research interest in this material class intensified. We used ozone assisted molecular beam epitaxy to grow RNiO₃ thin films (R=La,Pr) and investigated the subsequent topotactic soft-chemistry reaction, needed to synthesize the square-planar phase, at different stages of reduction by x-ray absorption spectroscopy. We observe the evolution of the Ni oxidation state and that the process is laterally homogeneous down to length scales of 50 nm. To reach the superconducting phase hole doping of the infinite-layer nickelates is required with an optimal doping level around x=0.2. This can be achieved by self-doping in quintuple-layer Ruddlesden-Popper nickelates or alkaline-earth doping, Ca or Sr, in infinite-layer films. Using angle-resolved photoemission spectroscopy (ARPES) we studied changes in the Fermi surface upon alkaline-earth doping in (La,Ca)NiO₃.