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Dimensionality Control of Electronic Phase Transitions in Nickel-Oxide Superlattices

Boris, A.V., Matiks, Y., Benckiser, E., Frano, A., Popovich, P., Hinkov, V., Wochner, P., Castro-Colin, M., Detemple, E., Malik, V.K., Bernhard, C., Prokscha, T., Suter, A., Salman, Z., Morenzoni, E., Cristiani, G., Habermeier, H.-U., Keimer, B.
Science 2011 v.332 no.6032 pp. 937-940
electrons, ferrimagnetic materials, lanthanum, phase transition, temperature
The competition between collective quantum phases in materials with strongly correlated electrons depends sensitively on the dimensionality of the electron system, which is difficult to control by standard solid-state chemistry. We have fabricated superlattices of the paramagnetic metal lanthanum nickelate (LaNiO₃) and the wide-gap insulator lanthanum aluminate (LaAlO₃) with atomically precise layer sequences. We used optical ellipsometry and low-energy muon spin rotation to show that superlattices with LaNiO₃ as thin as two unit cells undergo a sequence of collective metal-insulator and antiferromagnetic transitions as a function of decreasing temperature, whereas samples with thicker LaNiO₃ layers remain metallic and paramagnetic at all temperatures. Metal-oxide superlattices thus allow control of the dimensionality and collective phase behavior of correlated-electron systems.