Fine-tuning orbitals by breaking symmetry
“Tuning” the structure and composition of Transition-metal Oxides (TMO) gives researchers new insights into their behavior and potential for practical applications in electronics and materials science.
By using the XSD 33-ID-D,E beamline at the APS researchers are now controlling and manipulating orbital properties of TMO.
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 LaTiO3−LaNiO3−LaAlO3 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 LaNiO3 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.
Ankit S. Disa, Divine P. Kumah, Andrei Malashevich, Hanghui Chen, Dario A. Arena, Eliot D. Specht, Sohrab Ismail-Beigi, F. J. Walker, and Charles H. Ahn, “Orbital Engineering in Symmetry-Breaking Polar Heterostructures,” Physical Review Letters 114, 026801. DOI: 10.1103/PhysRevLett.114.026801, Published January 12, 2015.