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TT: Fachverband Tiefe Temperaturen

TT 20: Focus Session: The Nickel Age of Superconductivity: Cuprates Reloaded or Something New?

TT 20.6: Vortrag

Dienstag, 17. März 2020, 12:15–12:30, HSZ 03

Topotactic hydrogen in nickelate superconductors and akin infinite-layer oxides ABO₂ — •Karsten Held¹, Liang Si^1,2, Wen Xiao², Josef Kaufmann¹, Yi Lu³, Jan M. Tomczak¹, and Zhicheng Zhong² — ¹Institute for Solid State Physics, TU Wien, Austria — ²Chinese Academy of Science NIMTE, Ningbo, China — ³Institute for Theoretical Physics, Heidelberg University, Germany

The seminal work by Li et al. [1] opens the door wide to the nickelate age of superconductivity. But it appears to be most difficult to reproduce. Since the chemical reduction of ABO₃ (A: rare earth; B transition metal) with CaH₂ may result in both, ABO₂ and ABO₂H, we calculate [2] the topotactic H binding energy by density functional theory (DFT). We find intercalating H to be energetically favorable for LaNiO₂ and NdNiO₂ but not for Sr-doped NdNiO₂.

This topotactical hydrogen turns the electronic structure upside down. Our DFT+dynamical mean field theory calculations show [2] that 3d⁹ LaNiO₂ is similar to (doped) cuprates, whereas 3d⁸ LaNiO₂H is a two-orbital Mott insulator, similar to LaNiO₃|LaAlO₃ heterostructures prior to engineering their bandstructure to a cuprate-like one [3]. Topotactic H might hence explain why some nickelates are superconducting and others are not.

[1] D. Li et al., Nature 572, 624 (2019).

[2] L. Si, W. Xiao, J. Kaufmann, J.M. Tomczak, Y. Lu, Z. Zhong, K. Held, arXiv:1911.06917.

[3] P. Hansmann, X. Yang, A. Toschi, G. Khaliullin, O. K. Andersen, and K. Held, Phys. Rev. Lett. 103, 016401 (2009).