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|Title:||ALS Special Seminar | Hyang Keun Yoo|
|When:||02/28/2014 2:00 PM - 3:00 PM|
|Description:||ALS/CXRO Special Seminar|
Fri, Feb 28, 2014
6-2202 Conf Rm
Hyang Keun Yoo
Center for Correlated Electron Systems, Institute for Basic Science (IBS)/
Department of Physics and Astronomy, Seoul National University
Artificial control of the electronic structures
in strongly correlated LaNiO3 films investigated by in situ ARPES
Control over the electronic properties via heterostructuring has attracted much attention in correlated oxide systems. Recently, the electronic structure of the tensile-strained two-dimensional (2D) LaNiO3 (LNO) heterostructure has been theoretically predicted to have an orbital ordered insulating ground state, analogous to that of high-Tc cuprate superconductors. To clarify this intriguing electronic ground state in 2D LNO, we performed in situ ARPES studies on LNO ultrathin films.
(1) By using LaAlO3, NdGaO3, and SrTiO3 substrates, we could obtain 10-unit cells (UC)-thick LNO films which were under compressive, nearly free, and tensile strains, respectively. The eg bands of the LNO film are renormalized due to strong electronic correlations, and their positions are shifted depending on the strain states. Particularly, with tensile strain, the band crosses the Fermi level and changes the Fermi surface topology. As a result, in tensile-strained LNO film, we are able to observe Fermi surface superstructure which may be induced by spin density wave fluctuations. (2) We also prepared the LNO ultrathin films on SrTiO3 substrate with varying the film thickness from 1 to 10 UC. We observed that the dimensional crossover of the band structure occurs around 3 UC of LNO film. However, the theoretically predicted orbital ordering has not been achieved in 2D LNO ultrathin films. Instead, we found that its electronic structure becomes quasi-one-dimensional. The details are discussed more in presentation.