Regensburg 2025 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 52: Nickelates and Other Complex Oxides

TT 52.3: Vortrag

Freitag, 21. März 2025, 10:00–10:15, H31

Surface effects in infinite layer nickelates — •Leonard M. Verhoff¹, Liang Si^1,2, and Karsten Held¹ — ¹Institute of Solid State Physics, TU Wien, Vienna, Austria — ²School of Physics, Northwest University, Xi’an, China

Nickelates have emerged as a compelling platform for studying high-temperature superconductivity, drawing comparisons to cuprates. Infinite layer rare-earth (R) nickelates, RNiO₂, consist of an alternating stacking of NiO₂ layers and rare-earth spacing layers along the crystallographic z-axis. While their bulk structure has been extensively studied computationally, the samples that exhibit superconductivity in experiments are thin nickelate films. They are synthesized through a chemical reduction process that removes apical oxygen from perovskite RNiO₃, often grown on substrates such as SrTiO₃ (001).
We explore emerging surface effects by studying the formation of various surfaces within the framework of DFT. While perfect stoichiometry favors a NiO₂-terminated surface, the presence of excess apical oxygen in the surface region – possibly a remnant of the chemical reduction process – might favor an RO-terminated surface. The atomic structures of the studied surfaces strongly influence the local electronic structure in the surface region. These surface effects indicate the absence of an electron pocket around the Γ point – even for NdNiO₂ surfaces, in contrast to DFT and dynamical mean field theory bulk calculations.
We acknowledge support through a joint German and Austrian Science Funds (DFG and FWF) project; IWF project ID I5398.

Keywords: DFT; Nickelates; Surface