Strain-driven disproportionation at a correlated oxide metal-insulator transition

Authors

T. H. Kim, University of Wisconsin–Madison
Tula R. Paudel, UNLFollow
R. J. Green, University of British Columbia, University of Saskatchewan
K. Song, Korea Institute of Materials Science
H.-S. Lee, Korea Institute of Materials Science
S.-Y. Choi, Pohang University of Science and Technology
J. Irwin, University of Wisconsin–Madison
B. Noesges, The Ohio State University
L. J. Brillson, The Ohio State University
M. S. Rzchowski, University of Wisconsin–Madison
G. A. Sawatzky, University of British Columbia
Evgeny Y. Tsymbal, University of Nebraska at LincolnFollow
C. B. Eom, University of Wisconsin–Madison

Date of this Version

3-9-2020

Citation

T. H. KIM et al. PHYSICAL REVIEW B 101, 121105(R) (2020). DOI: 10.1103/PhysRevB.101.121105

Comments

Used by permission.

Abstract

Metal-to-insulator phase transitions in complex oxide thin films are exciting phenomena which may be useful for device applications, but in many cases the physical mechanism responsible for the transition is not fully understood. Here we demonstrate that epitaxial strain generates local disproportionation of the NiO₆ octahedra, driven through changes in the oxygen stoichiometry, and that this directly modifies the metal-to-insulator phase transition in epitaxial (001) NdNiO₃ thin films. Theoretically, we predict that the Ni-O-Ni bond angle decreases, while octahedral tilt and local disproportionation of the NiO₆ octahedra increases resulting in a small band gap in an otherwise metallic system. This is driven by an increase in oxygen vacancy concentration in the rare-earth nickelates with increasing in-plane biaxial tensile strain. Experimentally, we find an increase in pseudocubic unit-cell volume and resistivity with increasing biaxial tensile strain, corroborating our theoretical predictions. With electron-energy-loss spectroscopy and x-ray absorption, we find a reduction of the Ni valence with increasing tensile strain. These results indicate that epitaxial strain modifies the oxygen stoichiometry of rare-earth perovskite thin films and through this mechanism affects the metal-to-insulator phase transition in these compounds.