Confinement-driven metal-insulator transition and polarity-controlled conductivity of epitaxial LaNiO3/LaAlO3 (111) superlattices

2016 
Recently, topological conductivity has been predicted theoretically in LaNiO3(111)-based superlattices. Here we report high-quality epitaxial LaNiO3/LaAlO3 superlattices on (111)-oriented SrTiO3 and LaAlO3 single crystals. For both substrates a metal-insulator transition with decreasing number of LaNiO3 monolayers is found. While the electrical transport is dominated by two-dimensional variable range hopping for superlattices grown on polar mismatched SrTiO3(111), it switches to a thermally activated single gap behavior on polar matched LaAlO3(111). The gap energy of the polar double-layer LaNiO3 superlattices can be tuned via the thickness of the insulating LaAlO3 layers.
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