Yimei Zhu, Atomically Resolved Interfacial Coupling and Polarization of ABO3 Heterostructures

Yimei Zhu

Department of Condensed Mater Physics and Materials Science
Brookhaven National Laboratory, Upton, NY 11973 USA

Interfaces with subtle difference in atomic and electronic structures in perovskite ABO3 heterostructures often yield intriguingly different properties, yet their exact roles remain elusive. In this presentation, we report an integrated study of unusual transport, magnetic, and structural properties of Pr0.67Sr0.33MnO3 films and La0.67Sr0.33MnO3 films of various thicknesses on SrTiO3 (STO) substrate. In particular, using atomically resolved imaging and electron energy-loss spectroscopy, we measure interface related local lattice distortion, BO6 octahedral rotation and cation-anion displacement induced polarization. In the very thin Pr0.67Sr0.33MnO3 film, an unexpected interface-induced ferromagnetic polaronic insulator phase was observed during the cubic-to-tetragonal phase transition of STO, due to the enhanced electron-phonon interaction and atomic disorder in the film. For the very thin La0.67Sr0.33MnO3 films we reveal a remarkably deep polarization in non-ferroelectric STO near the interface due to its build-in electric field. Combining the experimental results including electron holography with first principles calculations, we propose that the observed deep polarization and field are originated from oxygen vacancies that extend beyond a dozen unit-cells from the interface, thus providing important evidence of the role of defects in the emergent interface properties of transition metal oxides.

The work was supported by DOE-BES-MSE under Contract DE-AC02-98CH10886. Collaborations with L. Wu, B. Zhang, G. M. Chow, Z. Wang, J. Tao, L. Yu, M-G. Han, J. Zhang, and E. W. Plummer are acknowledged.

Plenary lectures - YUCOMAT 2017

member since 2008