Atomic-scale control of oxide heteroepitaxy is of growing importance from the viewpoints of fundamental physics and device applications. Many of intriguing physical phenomena occur in naturally layered structures of transition-metal oxides, leading to recent focuses on "epitaxial" design of new compounds upon the layer-by-layer growth of artificial superstructures. We have been studying magnetotransport properties of high-mobility electrons at polar oxide heterointerfaces. In the first case, we have created a metallic state in atomically abrupt heterointerface between two band insulators, SrTiO3 and LaAlO3 [1], in which naturally arising polarity discontinuity introduces high-mobility electrons in SrTiO3. Dramatic magnetoresistance oscillations appeared at low temperatures. Moreover, electric-field induced metal-insulator and superconductor-insulator transitions have been demonstrated. The second example is ZnO/MgZnO heterostructures, in which we have recently succeeded in observing fractional quantum Hall effect [2]. These results have implications for all oxide heteroepitaxial devices. In particular, the high mobilities achieved present the possibility to combine the world of oxides (superconductors, multiferroics, colossal magnetoresistance) with the world of semiconductor heterostructures.
[1] A. Ohtomo and H. Y. Hwang, Nature 427, 423-426 (2004). [2] A. Tsukazaki, A. Ohtomo, M. Kawasaki, et al. Nat. Mater. 9, 889-893 (2010)
各種検索
サポート
ヘルプ