Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
Science. 2011 May 20;332(6032):937-40. doi: 10.1126/science.1202647.
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 (LaNiO(3)) and the wide-gap insulator lanthanum aluminate (LaAlO(3)) with atomically precise layer sequences. We used optical ellipsometry and low-energy muon spin rotation to show that superlattices with LaNiO(3) 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 LaNiO(3) 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.
在强关联电子材料中，集体量子相之间的竞争强烈依赖于电子系统的维度，这很难通过标准的固态化学来控制。我们已经制备了具有原子级精确层序的顺磁金属镍酸镧（LaNiO(3)）和宽带隙绝缘体氧化铝镧（LaAlO(3)）的超晶格。我们使用光学椭圆偏振和低能μ子自旋旋转来表明，当温度降低时，厚度仅有两个单元的 LaNiO(3)超晶格经历了一系列集体金属-绝缘体和反铁磁转变，而具有较厚 LaNiO(3)层的样品在所有温度下都保持金属性和顺磁性。因此，金属氧化物超晶格允许控制关联电子系统的维度和集体相行为。
