Abstract
The metal-insulator transition and the underlying electronic and orbital structure in quantum wells based on were investigated by dc 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 metal-insulator transition are found to be strongly enhanced under quantum confinement by sandwiching with the wide-gap dielectric , 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 orbital splitting when interfaced with the confining layer.
- Received 26 November 2011
DOI:https://doi.org/10.1103/PhysRevLett.109.107402
© 2012 American Physical Society