• Open Access

Electronic Character of Charge Order in Square-Planar Low-Valence Nickelates

Y. Shen, J. Sears, G. Fabbris, J. Li, J. Pelliciari, M. Mitrano, W. He, Junjie Zhang, J. F. Mitchell, V. Bisogni, M. R. Norman, S. Johnston, and M. P. M. Dean
Phys. Rev. X 13, 011021 – Published 21 February 2023
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Abstract

Charge order is a central feature of the physics of cuprate superconductors and is known to arise from a modulation of holes with primarily oxygen character. Low-valence nickelate superconductors also host charge order, but the electronic character of this symmetry breaking is unsettled. Here, using resonant inelastic x-ray scattering at the Ni L2 edge, we identify intertwined involvements of Ni 3dx2y2, 3d3z2r2, and O 2pσ orbitals in the formation of diagonal charge order in an overdoped low-valence nickelate La4Ni3O8. The Ni 3dx2y2 orbitals, strongly hybridized with planar O 2pσ, largely shape the spatial charge distribution and lead to Ni site-centered charge order. The 3d3z2r2 orbitals play a small, but non-negligible role in the charge order as they hybridize with the rare-earth 5d orbitals. Our results reveal that the low-energy physics and ground-state character of these nickelates are more complex than those in cuprates.

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  • Received 19 August 2022
  • Revised 20 December 2022
  • Accepted 10 January 2023

DOI:https://doi.org/10.1103/PhysRevX.13.011021

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Y. Shen1,*, J. Sears1, G. Fabbris2, J. Li3, J. Pelliciari3, M. Mitrano4, W. He1, Junjie Zhang5,6, J. F. Mitchell5, V. Bisogni3, M. R. Norman5, S. Johnston7,8, and M. P. M. Dean1,7,†

  • 1Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
  • 2Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA
  • 3National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, USA
  • 4Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
  • 5Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
  • 6Institute of Crystal Materials, Shandong University, Jinan, Shandong 250100, China
  • 7Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37966, USA
  • 8Institute of Advanced Materials and Manufacturing, The University of Tennessee, Knoxville, Tennessee 37996, USA

  • *yshen@bnl.gov
  • mdean@bnl.gov

Popular Summary

Electrons in copper-based high-temperature superconductors tend to arrange themselves in periodic structures leading to a modulation in their charge density. These arrangements significantly affect the physical properties of these materials. Thus, it is natural to ask whether similar charge order exists in the newly found low-valence nickelate superconductors and what the corresponding electronic characteristics are. Here, we report that charge modulation does exist in one such superconductor and that the low-energy physics and ground-state character of these nickelates are more complex than those in cuprates.

Answering these questions requires an experimental tool that can detect charge modulations and resolve the contributions from different electronic orbitals. We show that resonant inelastic x-ray scattering provides one such tool. Applying it to La4Ni3O8, the trilayer member of the low-valence nickelate family, we find that charge modulation mostly takes place on nickel orbitals with appreciable contributions from the surrounding oxygen sites. The rare-earth atoms, which lie above and below the nickel-oxygen layers, play a minimal, although nonzero, role in charge order formation.

Our results establish the essential electronic ingredients for the charge order in low-valence nickelates, paving the way to a comprehensive understanding of this new family of superconductors and their relationship to the cuprates.

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Vol. 13, Iss. 1 — January - March 2023

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