Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06511, USA and Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA.
Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06511, USA and Department of Applied Physics, Yale University, New Haven, Connecticut 06511, USA and Department of Physics, Columbia University, New York, New York 10027, USA and Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA.
Phys Rev Lett. 2015 Jan 16;114(2):026801. doi: 10.1103/PhysRevLett.114.026801. Epub 2015 Jan 12.
We experimentally demonstrate a novel approach to substantially modify orbital occupations and symmetries in electronically correlated oxides. In contrast to methods using strain or confinement, this orbital tuning is achieved by exploiting charge transfer and inversion symmetry breaking using atomically layered heterostructures. We illustrate the technique in the LaTiO_{3}-LaNiO_{3}-LaAlO_{3} system; a combination of x-ray absorption spectroscopy and ab initio theory reveals electron transfer and concomitant polar fields, resulting in a ∼50% change in the occupation of Ni d orbitals. This change is sufficiently large to remove the orbital degeneracy of bulk LaNiO_{3} and creates an electronic configuration approaching a single-band Fermi surface. Furthermore, we theoretically show that such three-component heterostructuring is robust and tunable by choice of insulator in the heterostructure, providing a general method for engineering orbital configurations and designing novel electronic systems.
我们实验证明了一种新颖的方法，可以在电子相关氧化物中显著改变轨道占据和对称性。与使用应变或限制的方法不同，这种轨道调谐是通过利用原子层状异质结构中的电荷转移和反转对称性破坏来实现的。我们在 LaTiO_{3}-LaNiO_{3}-LaAlO_{3} 系统中说明了该技术；X 射线吸收光谱和第一性原理理论的结合揭示了电子转移和伴随的极场，导致 Ni d 轨道占据的变化约为 50%。这种变化足以消除块状 LaNiO_{3}的轨道简并性，并产生接近单带费米表面的电子构型。此外，我们从理论上表明，这种三组分异质结构是稳健的，并且可以通过异质结构中绝缘体的选择进行调谐，为工程轨道构型和设计新型电子系统提供了一种通用方法。
