Structural signatures of the insulator-to-metal transition in BaCo1xNixS2

Emily C. Schueller, Kyle D. Miller, William Zhang, Julia L. Zuo, James M. Rondinelli, Stephen D. Wilson, and Ram Seshadri
Phys. Rev. Materials 4, 104401 – Published 1 October 2020
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Abstract

The solid solution BaCo1xNixS2 exhibits an insulator-to-metal transition close to x=0.21. Questions of whether this transition is coupled with structural changes remain open. Here we follow the structural evolution as a function of the Ni content x using synchrotron powder x-ray diffraction and pair distribution function analyses to reveal significant basal sulfide anion displacements occurring preferentially along the CoS5 pyramidal edges comprising the edge-connected bond network in BaCo1xNixS2. These displacements decrease in magnitude as x increases and are nearly quenched in x=1BaNiS2. Density-functional-theory-based electronic structure calculations on x=0BaCoS2 suggest that these displacements arise as a dynamic first-order Jahn-Teller effect owing to partial occupancy of nominally degenerate Co2+dxz and dyz orbitals, leading to local structural symmetry breaking in the xy-plane of the Co-rich phases. The Jahn-Teller instability is associated with the opening of a band gap that is further strengthened by electronic correlation. The Jahn-Teller effect is reduced upon increased electron filling as x1, indicating that the local structure and band filling cooperatively result in the observed insulator-to-metal transition.

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  • Received 14 July 2020
  • Accepted 14 September 2020

DOI:https://doi.org/10.1103/PhysRevMaterials.4.104401

©2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Emily C. Schueller1, Kyle D. Miller2, William Zhang1, Julia L. Zuo1, James M. Rondinelli2, Stephen D. Wilson1, and Ram Seshadri1,3

  • 1Materials Department and Materials Research Laboratory, University of California, Santa Barbara, Santa Barbara, California 93106, USA
  • 2Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
  • 3Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, USA

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Vol. 4, Iss. 10 — October 2020

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