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Title: Orbital Engineering in Nickelate Heterostructures Driven by Anisotropic Oxygen Hybridization rather than Orbital Energy Levels

We used resonant inelastic x-ray scattering to investigate the electronic origin of orbital polarization in nickelate heterostructures taking LaTiO3-LaNiO3-3×(LaAlO3), a system with exceptionally large polarization, as a model system. Furthermore, we find that heterostructuring generates only minor changes in the Ni 3d orbital energy levels, contradicting the often-invoked picture in which changes in orbital energy levels generate orbital polarization. Instead, O K-edge x-ray absorption spectroscopy demonstrates that orbital polarization is caused by an anisotropic reconstruction of the oxygen ligand hole states. This also provides an explanation for the limited success of theoretical predictions based on tuning orbital energy levels and implies that future theories should focus on anisotropic hybridization as the most effective means to drive large changes in electronic structure and realize novel emergent phenomena.
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [3] ;  [2] ;  [2] ;  [2] ;  [5] ;  [5] ;  [4] ;  [6] ;  [3] ;  [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States). Dept. of Condensed Matter Physics and Materials Science
  2. National Synchrotron Radiation Research Center, Hsinchu (Taiwan)
  3. Paul Scherrer Inst. (PSI), Villigen (Switzerland). Research Dept.
  4. Yale Univ., New Haven, CT (United States). Dept. of Applied Physics
  5. Yale Univ., New Haven, CT (United States). Dept. of Applied Physics and Dept. of Mechanical Engineering and Materials Science
  6. National Synchrotron Radiation Research Center, Hsinchu (Taiwan); National Tsing Hua Univ., Hsinchu (Taiwan). Dept. of Physics
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0031-9007; PRLTAO; R&D Project: PO011; KC0201060
Grant/Contract Number:
SC00112704; 1047478
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 117; Journal Issue: 14; Journal ID: ISSN 0031-9007
American Physical Society (APS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States