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Mechanisms of charge transfer and redistribution in LaAlO3/SrTiO3 revealed by high-energy optical conductivity

Author

Listed:
  • T.C. Asmara

    (NUSNNI-NanoCore, National University of Singapore
    National University of Singapore
    Singapore Synchrotron Light Source, National University of Singapore)

  • A. Annadi

    (NUSNNI-NanoCore, National University of Singapore
    National University of Singapore)

  • I. Santoso

    (NUSNNI-NanoCore, National University of Singapore
    National University of Singapore
    Singapore Synchrotron Light Source, National University of Singapore)

  • P.K. Gogoi

    (NUSNNI-NanoCore, National University of Singapore
    National University of Singapore
    Singapore Synchrotron Light Source, National University of Singapore)

  • A. Kotlov

    (Hamburger Synchrotronstrahlungslabor (HASYLAB) at Deutsches Elektronen-Synchrotron (DESY))

  • H.M. Omer

    (Singapore Synchrotron Light Source, National University of Singapore)

  • M. Motapothula

    (NUSNNI-NanoCore, National University of Singapore
    National University of Singapore
    Center for Ion Beam Applications (CIBA), National University of Singapore)

  • M.B.H. Breese

    (National University of Singapore
    Singapore Synchrotron Light Source, National University of Singapore
    Center for Ion Beam Applications (CIBA), National University of Singapore)

  • M. Rübhausen

    (NUSNNI-NanoCore, National University of Singapore
    Institut für Angewandte Physik, Universität Hamburg
    Center for Free Electron Laser Science (CFEL))

  • T. Venkatesan

    (NUSNNI-NanoCore, National University of Singapore
    National University of Singapore
    National University of Singapore)

  • Ariando

    (NUSNNI-NanoCore, National University of Singapore
    National University of Singapore)

  • A. Rusydi

    (NUSNNI-NanoCore, National University of Singapore
    National University of Singapore
    Singapore Synchrotron Light Source, National University of Singapore)

Abstract

In condensed matter physics the quasi two-dimensional electron gas at the interface of two different insulators, polar LaAlO3 on nonpolar SrTiO3 (LaAlO3/SrTiO3) is a spectacular and surprising observation. This phenomenon is LaAlO3 film thickness dependent and may be explained by the polarization catastrophe model, in which a charge transfer of 0.5e− from the LaAlO3 film into the LaAlO3/SrTiO3 interface is expected. Here we show that in conducting samples (≥4 unit cells of LaAlO3) there is indeed a ~0.5e− transfer from LaAlO3 into the LaAlO3/SrTiO3 interface by studying the optical conductivity in a broad energy range (0.5–35 eV). Surprisingly, in insulating samples (≤3 unit cells of LaAlO3) a redistribution of charges within the polar LaAlO3 sublayers (from AlO2 to LaO) as large as ~0.5e− is observed, with no charge transfer into the interface. Hence, our results reveal the different mechanisms for the polarization catastrophe compensation in insulating and conducting LaAlO3/SrTiO3 interfaces.

Suggested Citation

  • T.C. Asmara & A. Annadi & I. Santoso & P.K. Gogoi & A. Kotlov & H.M. Omer & M. Motapothula & M.B.H. Breese & M. Rübhausen & T. Venkatesan & Ariando & A. Rusydi, 2014. "Mechanisms of charge transfer and redistribution in LaAlO3/SrTiO3 revealed by high-energy optical conductivity," Nature Communications, Nature, vol. 5(1), pages 1-10, May.
    • Handle: RePEc:nat:natcom:v:5:y:2014:i:1:d:10.1038_ncomms4663
    DOI: 10.1038/ncomms4663
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