Quantization condition of strongly correlated electrons in oxide nanostructures

Abstract

Some oxide nanostructures have recently been shown to host quantum well (QW) states that are promising for quantum device applications by designing the wave function of their strongly correlated electrons. However, it is unclear why QW states only appear in certain oxides, limiting the possibilities of wave-function engineering. Here, we demonstrate that the electron mean free path λ is one of the essential conditions to form standing waves of strongly correlated electrons in oxide nanostructures. We have investigated the QW states formed in SrTi1–xVxO3 (STVO) ultrathin films using in situ angle-resolved photoemission spectroscopy. The controllability of λ in STVO while maintaining an atomically flat surface and chemically abrupt interface enables us to examine the evolution of QW states with varying λ. A detailed analysis reveals that the intensity of the QW states is almost linearly correlated to λ and may disappear at the Ioffe–Regel criterion, corresponding to the nearest neighbor inter-vanadium distance in STVO. Our findings provide design guidelines for creating and controlling novel quantum phenomena in oxide nanostructures.