Metal-insulator transition and orbital reconstruction in Mott quantum wells of NdNiO$_{3}$

TL;DR

This study investigates how quantum confinement and boundary conditions in NdNiO$_{3}$ quantum wells influence the metal-insulator transition and orbital structure, revealing that interface engineering can control electronic phases.

Contribution

It demonstrates that the boundary conditions in NdNiO$_{3}$ quantum wells critically determine the electronic ground state and transition behavior, highlighting the role of interface design in correlated oxides.

Findings

Quantum well boundary conditions significantly affect the MIT.

Sandwich structures enhance charge ordering and MIT.

Surface interfaces suppress long-range orderings.

Abstract

The metal-insulator transition (MIT) and the underlying electronic and orbital structure in $e_{g}^{1}$ quantum wells based on NdNiO$_{3}$ was investigated by d.c. transport and resonant soft x-ray absorption spectroscopy. By comparing quantum wells of the same dimension but with two different confinement structures, we explicitly demonstrate that the quantum well boundary condition of correlated electrons is critical to selecting the many-body ground state. In particular, the long-range orderings and the MIT are found to be strongly enhanced under quantum confinement by sandwiching NdNiO$_{3}$ with the wide-gap dielectric LaAlO$_{3}$, while they are suppressed when one of the interfaces is replaced by a surface (interface with vacuum). Resonant spectroscopy reveals that the reduced charge fluctuations in the sandwich structure are supported by the enhanced propensity to charge ordering due to the suppressed $e_g$ orbital splitting when interfaced with the confining LaAlO$_{3}$ layer.