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Interface engineering of novel quantum phenomena in digital transition metal oxide heterostructures

Transition metal oxides (TMOs) have long been one of the main subjects of material science because of their novel functionalities such as high-Tc superconductivity in cuprates and the colossal magnetoresistance effect in manganites. A new era for the study of novel oxides was opened by the recent developments in thin film growth techniques with the atomic precision. A variety of heterostructures involving TMOs have been fabricated and characterized, leading to, for example, the discovery of 2-dimensional electron gases at interfaces between two dissimilar insulators [1]. Thus, further novel phenomena may emerge in such TMO heterostructures. In this talk, I will present our recent theoretical developments on oxide heterostructures along with this direction. Specifically, I consider bilayers of TMOs grown along the [111] crystallographic axis. A variety of novel phenomena are predicted, including quantum spin Halll effects [2] and anomalous Hall effects [3]. The effect of strong correlation is also discussed in the presence of strong spin-orbit coupling. For some cases, the low-energy effective Hamiltonian is given by the sum of the Heisenberg interaction and the Kitaev interaction [4]. Detailed phase behavior for such a model is discussed for a wide range of parameters [5].

[1] A. Ohtomo & H. Y. Hwang, Nature 427, 423?426 (2004).

[2] D. Xiao, W. Zhu, Y. Ran, N. Nagaosa, and S. Okamoto, Nat. Commun. 2:596 doi: 10.1038/ncomms1602 (2011).

[3] K.-Y. Yang, W. Zhu, D. Xiao, S. Okamoto, Z. Wang, and Y. Ran, Phys. Rev. B 84, 201104(R) (2011).

[4] S. Okamoto, arXiv:1210.2290.

[5] S. Okamoto, arXiv:1212.5218

Research supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division.