Tuning A Strain-Induced Orbital Selective Mott Transition In Epitaxial Vo2
PHYSICAL REVIEW B(2016)
Abstract
We present evidence of strain-induced modulation of electron correlation effects and increased orbital anisotropy in the rutile phase of epitaxial VO2/TiO2 films from hard x-ray photoelectron spectroscopy and soft V L-edge x-ray absorption spectroscopy, respectively. By using the U(1) slave spin formalism, we further argue that the observed anisotropic correlation effects can be understood by a model of orbital selective Mott transition at a filling that is noninteger but close to the half filling. Because the overlaps of wave functions between d orbitals are modified by the strain, orbital-dependent renormalizations of the bandwidths and the onsite energy occur. These renormalizations generally result in different occupation numbers in different orbitals. We find that if the system has a noninteger filling number near the half filling such as for VO2, certain orbitals could reach an occupation number closer to half filling under the strain, resulting in a strong reduction in the quasiparticle weight Z(alpha) of that orbital. Our work demonstrates that such an orbital selective Mott transition, defined as the case with Z(alpha) = 0 in some but not all orbitals, could be accessed by epitaxial-strain engineering of correlated electron systems.
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Key words
Spin-Orbit Coupling,Spin State Transition,Metal-Insulator Transition
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