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Cooperative effects of strain and electron correlation in epitaxial VO2 and NbO2
Authors:
Wei-Cheng
Lee
(Binghamton University)
,
Matthew
Wahila
(Binghamton University)
,
Shantanu
Mukherjee
(Indian Institute of Technology Madras)
,
Christopher N.
Singh
(Binghamton University)
,
Tyler
Eustance
(Binghamton University)
,
Anna
Regoutz
(Imperial College London)
,
Hanjong
Paik
(Cornell University)
,
Jos E.
Boschker
(Leibniz-Institut für Kristallzüchtung)
,
Fanny
Rodolakis
(Argonne National Laboratory)
,
Tien-Lin
Lee
(Diamond Light Source)
,
Darrell G.
Schlom
(Cornell University)
,
Louis F. J.
Piper
(Binghamton University)
Co-authored by industrial partner:
No
Type:
Journal Paper
Journal:
Journal Of Applied Physics
, VOL 125
State:
Published (Approved)
Published:
February 2019
Diamond Proposal Number(s):
20647
,
21430
Abstract: We investigate the electronic structure of epitaxial VO 2 2 films in the rutile phase using density functional theory combined with the slave-spin method (DFT + SS). In DFT + SS, multi-orbital Hubbard interactions are added to a DFT-fit tight-binding model, and slave spins are used to treat electron correlations. We find that while stretching the system along the rutile c c -axis results in a band structure favoring anisotropic orbital fillings, electron correlations favor equal filling of the t 2g t2g orbitals. These two distinct effects cooperatively induce an orbital-dependent redistribution of the electron occupations and spectral weights, driving strained VO 2 2 toward an orbital selective Mott transition (OSMT). The simulated single-particle spectral functions are directly compared to V L-edge resonant X-ray photoemission spectroscopy of epitaxial 10 nm VO 2 2 /TiO 2 2 (001) and (100) strain orientations. Excellent agreement is observed between the simulations and experimental data regarding the strain-induced evolution of the lower Hubbard band. Simulations of rutile NbO 2 2 under similar strain conditions are performed, and we predict that an OSMT will not occur in rutile NbO 2 2 . Our prediction is supported by the high-temperature hard x-ray photoelectron spectroscopy measurement on relaxed NbO 2 2 (110) thin films with no trace of the lower Hubbard band. Our results indicate that electron correlations in VO 2 2 are important and can be modulated even in the rutile phase before the Peierls instability sets in.
Journal Keywords: Epitaxy; X-ray photoelectron spectroscopy; Transition metal oxides; Electronic correlation; Tight-binding model; Phase transitions; Electronic bandstructure; Density functional theory
Subject Areas:
Physics,
Materials
Instruments:
I09-Surface and Interface Structural Analysis
Added On:
22/03/2019 16:15
Discipline Tags:
Surfaces
Physics
Hard condensed matter - structures
Materials Science
interfaces and thin films
Technical Tags:
Spectroscopy
X-ray Photoelectron Spectroscopy (XPS)
Hard X-ray Photoelectron Spectroscopy (HAXPES)