Comparing Bulk and Layer Confined RNiO₃ to Disentangle Lattice and Electronic Effects in the Metal-Insulator Transition

The metal-insulator transition (MIT) of transition metal oxides is often associated with a simultaneous lattice and electronic symmetry breaking. We disentangle the effects of the electronic and lattice structure in the MIT of rare earth nickelates (RNiO₃) by comparing bulk and layer-confined NdNiO₃, using a combination of electronic structure and many-body methods[1,2,3]. We find that electronic confinement leads to an increase in the relative role of local interactions that favor an insulating symmetry-broken state. However, heterostructuring with another material leads to an increase in the lattice stiffness with respect to structural disproportionation caused by the interfacial octahedral coupling. Our work explains why nickelate heterostructures can have both a higher MIT temperature despite a weaker structural signature of the insulating state[4]. These results are of general relevance to the physics of transition-metal oxides.
[1]AB Georgescu et al arXiv:1810.00480
[2]OE. Peil et al arXiv:1809:03720
[3]Q Han and AJ Millis PRL 121, 067601(2018)
[4]A Disa et al PRM 1,024410(2017)