Kavli Affiliate: Ankit Disa
| First 5 Authors: Alexandru B. Georgescu, Oleg E. Peil, Ankit Disa, Antoine Georges, Andrew J. Millis
| Summary:
In complex oxide materials, changes in electronic properties are often
associated with changes in crystal structure, raising the question of the
relative roles of the electronic and lattice effects in driving the
metal-insulator transition. This paper presents a combined theoretical and
experimental analysis of the dependence of the metal-insulator transition of
NdNiO$_3$ on crystal structure, specifically comparing properties of bulk
materials to one and two layer samples of NdNiO$_3$ grown between multiple
electronically inert NdAlO$_3$ counterlayers in a superlattice. The comparison
amplifies and validates a theoretical approach developed in previous papers and
disentangles the electronic and lattice contributions, through an independent
variation of each. In bulk NdNiO$_3$ the correlations are not strong enough to
drive a metal-insulator transition by themselves: a lattice distortion is
required. Ultra-thin films exhibit two additional electronic effects and one
lattice-related effect. The electronic effects are quantum confinement, leading
to dimensional reduction of the electronic Hamiltonian, and an increase in
electronic bandwidth due to counterlayer induced bond angle changes. We find
that the confinement effect is much more important. The lattice effect is an
increase in stiffness due to the cost of propagation of the lattice
disproportionation into the confining material.
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