Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                

Ultrafast modification of the polarity at LaAlO3/SrTiO3 interfaces

A. Rubano, T. Günter, M. Fiebig, F. Miletto Granozio, L. Marrucci, and D. Paparo
Phys. Rev. B 97, 035438 – Published 25 January 2018
PDFHTMLExport Citation
Abstract
Authors
Article Text
  • INTRODUCTION
  • SHG THEORY FOR SURFACES AND INTERFACES
  • EXPERIMENT
  • RESULTS
  • DISCUSSION
  • CONCLUSIONS
  • ACKNOWLEDGMENTS
    • References

    Abstract

    Oxide growth with semiconductorlike accuracy has led to atomically precise thin films and interfaces that exhibit a plethora of phases and functionalities not found in the oxide bulk material. This has yielded spectacular discoveries such as the conducting, magnetic, and even superconducting LaAlO3/SrTiO3 interfaces separating two prototypical insulating perovskite materials. All these investigations, however, consider the static state at the interface, although studies on fast oxide interface dynamics would introduce a powerful degree of freedom to understanding the nature of the LaAlO3/SrTiO3 interface state. Here, we show that the polarization state at the LaAlO3/SrTiO3 interface can be optically enhanced or attenuated within picoseconds. Our observations are explained by a model based on charge propagation effects in the interfacial vicinity and transient polarization buildup at the interface.

    • Figure
    • Figure
    • Figure
    • Figure
    • Figure
    • Figure
    • Figure
    • Received 20 December 2016
    • Revised 4 January 2018

    DOI:https://doi.org/10.1103/PhysRevB.97.035438

    ©2018 American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Electric polarizationPhotoconductivitySurface states
    1. Physical Systems
    Interfaces
    1. Techniques
    Pump-probe spectroscopy
    Condensed Matter, Materials & Applied Physics

    Authors & Affiliations

    A. Rubano1,5, T. Günter2, M. Fiebig2,3, F. Miletto Granozio1,4, L. Marrucci1,5, and D. Paparo5,*

    • 1Dipartimento di Fisica, Università di Napoli “Federico II,” Complesso Universitario di Monte S. Angelo, via Cintia, 80126 Napoli, Italy
    • 2Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, Nussallee 14-16, 53115 Bonn, Germany
    • 3Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland
    • 4CNR-SPIN, Complesso Universitario di Monte S. Angelo, via Cintia, 80126 Napoli, Italy
    • 5Institute of Applied Science and Intelligent Systems, Via Campi Flegrei 34, 80078 Pozzuoli

    • *d.paparo@isasi.cnr.it

    Article Text (Subscription Required)

    Click to Expand

    References (Subscription Required)

    Click to Expand
    Issue

    Vol. 97, Iss. 3 — 15 January 2018

    Reuse & Permissions
    Access Options
    Author publication services for translation and copyediting assistance advertisement

    Authorization Required

    Log In
    Other Options
    ×

    Images

    • Figure 1
      Figure 1

      SHG pump-probe layout and geometry of the input/output light polarizations. The high-pass filter blocks the fundamental beam. The latter is removed during the photoinduced reflectivity measurements.

      Reuse & Permissions
    • Figure 2
      Figure 2

      (a) and (b) Temporal evolution of Δχ¯ext/χ¯ext for Nph=5.65×1020cm−3. Solid lines are fits (see text for details). Note the striking difference of the dynamics between insulating (orange and blue points) and conductive (green points) samples that points to a complex interplay of different photoinduced mechanisms better explained in the text.

      Reuse & Permissions
    • Figure 3
      Figure 3

      Time dependence of the relative change in the SHG signal in STO after an optical excitation generating a photocarrier density of Nph=1.13×1020cm−3 (data points). The fits reproduce this measured change (orange line) and its respective contributions from the charge-propagation (red line) and transient-polarization (blue line) mechanisms. SHG susceptibilities χ¯ probe (c) and (d) the local state at the interface and (a) and (b) the extended environment around it.

      Reuse & Permissions
    • Figure 4
      Figure 4

      Pump-induced changes in reflectivity as a function of the photocarrier density for the samples: (a) LS6, (b) LS2, and (c) STO.

      Reuse & Permissions
    • Figure 5
      Figure 5

      Dependence of the relative change in the SHG susceptibility of the charge-propagation and transient-polarization contributions as defined in Eq. (3) on the density of the optical excitation Nph. Symbols represent fits of Eq. (3) to measured data as in Fig. 3. The amplitudes have been normalized to the corresponding value of χ¯ at time t<0. Solid lines are fits (see text). Here and in Fig. 6 error bars indicate statistical errors at 68.3% of the confidence level obtained through a χ2 test as described in Ref. [30]. The error bars are missing when their extension is not larger than symbol size.

      Reuse & Permissions
    • Figure 6
      Figure 6

      Dependence of the relaxation constants defined in Eq. (3) on the density of the optical excitation in the three types of samples. Solid lines are fits (see text). Dot-dashed lines indicate values of relaxation constants that did not reveal a dependence on the photocarrier density and were therefore replaced with a single fitting parameter over all the photocarrier density range.

      Reuse & Permissions
    • Figure 7
      Figure 7

      Nonequilibrium charge dynamics near the LAO/STO and air/STO interfaces. (a) Band bending and different extension of the charge concentration associated, respectively, with the dxy-like and dxz,yz-like subbands of STO at the interface (as adapted from Refs. [18, 23]). We notice that the medium beyond the dashed line may be either air, like in bare STO, or a LAO overlayer. (b) Screening drift as the first process contributing to the charge-propagation mechanism. (c) Photo-Dember effect as the second process contributing to the charge-propagation mechanism (as adapted from Ref. [32]). (d) Interfacial charge trapping as the process contributing to the transient-polarization mechanism. Note the positive charge of the trapping center that induces an electric field that adds in phase to the existing quantum-well field, thus enhancing the interfacial polarity.

      Reuse & Permissions
    ×

    Sign up to receive regular email alerts from Physical Review B

    Log In

    Cancel
    ×

    Search

    Article Lookup

    Paste a citation or DOI
    Enter a citation
    ×