Alexander Boris (MPI-FKF)
The competition between collective quantum phases in materials with strongly correlated electron depends critically 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 LaNiO3 and the wide-gap insulator LaAlO3 with atomically precise layer sequences. Using low-energy muon spin rotation and optical ellipsometry, we show that superlattices with LaNiO3 as thin as two unit cells undergo a sequence of collective charge- and spin-ordering transitions as a function of decreasing temperature, whereas samples with thicker LaNiO3 layers remain paramagnetic and metallic at all temperatures. Metal-oxide superlattices thus allow facile control of the dimensionality and collective phase behavior of correlated-electron systems.