Extensive hydrogen incorporation is not necessary for superconductivity in topotactically reduced nickelates

Purnima P Balakrishnan; Dan Ferenc Segedin; Lin Er Chow; P Quarterman; Shin Muramoto; Mythili Surendran; Ranjan K Patel; Harrison LaBollita; Grace A Pan; Qi Song; Yang Zhang; Ismail El Baggari; Koushik Jagadish; Yu-Tsun Shao; Berit H Goodge; Lena F Kourkoutis; Srimanta Middey; Antia S Botana; Jayakanth Ravichandran; A Ariando; Julia A Mundy; Alexander J Grutter

doi:10.1038/s41467-024-51479-3

Extensive hydrogen incorporation is not necessary for superconductivity in topotactically reduced nickelates

Nat Commun. 2024 Aug 27;15(1):7387. doi: 10.1038/s41467-024-51479-3.

Authors

Purnima P Balakrishnan^#¹, Dan Ferenc Segedin^#², Lin Er Chow^#³, P Quarterman⁴, Shin Muramoto⁵, Mythili Surendran^{6

7}, Ranjan K Patel⁸, Harrison LaBollita⁹, Grace A Pan², Qi Song², Yang Zhang¹⁰, Ismail El Baggari¹⁰, Koushik Jagadish⁶, Yu-Tsun Shao^{6

11}, Berit H Goodge^{12

13

14}, Lena F Kourkoutis^{12

13}, Srimanta Middey⁸, Antia S Botana⁹, Jayakanth Ravichandran^{15

16

17}, A Ariando¹⁸, Julia A Mundy¹⁹, Alexander J Grutter²⁰

Affiliations

¹ NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA. [email protected].
² Department of Physics, Harvard University, Cambridge, MA, 02138, USA.
³ Department of Physics, Faculty of Science, National University of Singapore, Singapore, 117551, Singapore.
⁴ NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
⁵ Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
⁶ Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, 90089, USA.
⁷ Core Center for Excellence in Nano Imaging, University of Southern California, Los Angeles, CA, 90089, USA.
⁸ Department of Physics, Indian Institute of Science, Bengaluru, 560012, India.
⁹ Department of Physics, Arizona State University, Tempe, AZ, 85287, USA.
¹⁰ The Rowland Institute at Harvard, Harvard University, Cambridge, MA, 02138, USA.
¹¹ Core Center for Excellence in Nano Imaging, University of Southern California, 925 Bloom Walk, Los Angeles, CA, 90089, USA.
¹² School of Applied and Engineering Physics, Cornell University, Ithaca, NY, 14853, USA.
¹³ Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, 14853, USA.
¹⁴ Max Planck Institute for Chemical Physics of Solids, 01187, Dresden, Germany.
¹⁵ Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, 90089, USA. [email protected].
¹⁶ Core Center for Excellence in Nano Imaging, University of Southern California, Los Angeles, CA, 90089, USA. [email protected].
¹⁷ Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, 90089, USA. [email protected].
¹⁸ Department of Physics, Faculty of Science, National University of Singapore, Singapore, 117551, Singapore. [email protected].
¹⁹ Department of Physics, Harvard University, Cambridge, MA, 02138, USA. [email protected].
²⁰ NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA. [email protected].

^# Contributed equally.

Abstract

A key open question in the study of layered superconducting nickelate films is the role that hydrogen incorporation into the lattice plays in the appearance of the superconducting state. Due to the challenges of stabilizing highly crystalline square planar nickelate films, films are prepared by the deposition of a more stable parent compound which is then transformed into the target phase via a topotactic reaction with a strongly reducing agent such as CaH₂. Recent studies, both experimental and theoretical, have introduced the possibility that the incorporation of hydrogen from the reducing agent into the nickelate lattice may be critical for the superconductivity. In this work, we use secondary ion mass spectrometry to examine superconducting La_1-xX_xNiO₂ / SrTiO₃ (X = Ca and Sr) and Nd₆Ni₅O₁₂ / NdGaO₃ films, along with non-superconducting NdNiO₂ / SrTiO₃ and (Nd,Sr)NiO₂ / SrTiO₃. We find no evidence for extensive hydrogen incorporation across a broad range of samples, including both superconducting and non-superconducting films. Theoretical calculations indicate that hydrogen incorporation is broadly energetically unfavorable in these systems, supporting our conclusion that extensive hydrogen incorporation is not generally required to achieve a superconducting state in layered square-planar nickelates.