Site-specific structure at multiple length scales in kagome quantum spin liquid candidates

Rebecca W. Smaha, Idris Boukahil, Charles J. Titus, Jack Mingde Jiang, John P. Sheckelton, Wei He, Jiajia Wen, John Vinson, Suyin Grass Wang, Yu-Sheng Chen, Simon J. Teat, Thomas P. Devereaux, C. Das Pemmaraju, and Young S. Lee
Phys. Rev. Materials 4, 124406 – Published 14 December 2020
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Abstract

Realizing a quantum spin liquid (QSL) ground state in a real material is a leading issue in condensed matter physics research. In this pursuit, it is crucial to fully characterize the structure and influence of defects, as these can significantly affect the fragile QSL physics. Here, we perform a variety of cutting-edge synchrotron x-ray scattering and spectroscopy techniques, and we advance new methodologies for site-specific diffraction and L-edge Zn absorption spectroscopy. The experimental results along with our first-principles calculations address outstanding questions about the local and long-range structures of the two leading kagome QSL candidates, Zn-substituted barlowite Cu3ZnxCu1x(OH)6FBr and herbertsmithite Cu3Zn(OH)6Cl2. On all length scales probed, there is no evidence that Zn substitutes onto the kagome layers, thereby preserving the QSL physics of the kagome lattice. Our calculations show that antisite disorder is not energetically favorable and is even less favorable in Zn-barlowite compared to herbertsmithite. Site-specific x-ray diffraction measurements of Zn-barlowite reveal that Cu2+ and Zn2+ selectively occupy distinct interlayer sites, in contrast to herbertsmithite. Using the first measured Zn L-edge inelastic x-ray absorption spectra combined with calculations, we discover a systematic correlation between the loss of inversion symmetry from pseudo-octahedral (herbertsmithite) to trigonal prismatic coordination (Zn-barlowite) with the emergence of a new peak. Overall, our measurements suggest that Zn-barlowite has structural advantages over herbertsmithite that make its magnetic properties closer to an ideal QSL candidate: its kagome layers are highly resistant to nonmagnetic defects while the interlayers can accommodate a higher amount of Zn substitution.

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  • Received 3 October 2020
  • Accepted 17 November 2020

DOI:https://doi.org/10.1103/PhysRevMaterials.4.124406

©2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Rebecca W. Smaha1,2,*, Idris Boukahil3,4,†, Charles J. Titus3,†, Jack Mingde Jiang1,5,†, John P. Sheckelton1, Wei He1,6, Jiajia Wen1, John Vinson7, Suyin Grass Wang8, Yu-Sheng Chen8, Simon J. Teat9, Thomas P. Devereaux1,6, C. Das Pemmaraju4, and Young S. Lee1,5,‡

  • 1Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
  • 2Department of Chemistry, Stanford University, Stanford, California 94305, USA
  • 3Department of Physics, Stanford University, Stanford, California 94305, USA
  • 4Theory Institute for Materials and Energy Spectroscopies, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
  • 5Department of Applied Physics, Stanford University, Stanford, California 94305, USA
  • 6Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA
  • 7Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA
  • 8NSF's ChemMatCARS, Center for Advanced Radiation Sources, c/o Advanced Photon Source/ANL, The University of Chicago, Argonne, Illinois 60439, USA
  • 9Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

  • *rsmaha@stanford.edu
  • These authors contributed equally to this work
  • youngsl@stanford.edu

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Issue

Vol. 4, Iss. 12 — December 2020

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