Metal-insulator transition in nanostructured SrTiO$_3$/LaAlO$_3$

ORAL

Abstract

It is well known that an insulator-to-metal transition occurs at SrTiO$_3$/LaAlO$_3$ epitaxial heterostructures when the number of LaAlO$_3$ layers reaches a critical value of four. With first-principles calculations, we show that instead of requiring the threshold number of layers to trigger metallicity, the so-called 1+2 overlayer heterostructure also exhibits metallic states. Interestingly, we demonstrate that these metallic states form a two-dimensional electron gas at the overlayer heterostructure. We understand that these fascinating phenomena originate from a modified ``polar catastrophe" model, where the overlayer heterostructure accumulates an electrostatic potential more rapidly than regular heterostructures, leading to the reduction of number of LAO layers. Using this model, we further show that the thinner 1+1 overlayer heterostructure exhibits a similar 2DEG. Our work provides a novel approach of inducing 2DEGs in oxide heterostructures, which are beneficial for modern electronics applications.

*HZ,PRCK,VRC and PG were sponsored by the LDRD at ORNL for the U.S. DOE and HX by the University of Tennessee JDRD and UT/ORNL-JIAM programs.

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Authors

  • Houlong Zhuang

    • CNMS, Oak Ridge National Laboratory
    • Center for Nanophase Materials Sciences, Oak Ridge National Laboratory
    • Oak Ridge National Lab

  • Valentino Cooper

    • MSTD, Oak Ridge National Laboratory
    • Oak Ridge National Lab
    • Materials Science and Technology Division, ORNL
    • Oak Ridge National Laboratory
    • Materials Science and Technology Division; Oak Ridge National Laboratory

  • P. Ganesh

    • CNMS, Oak Ridge National Laboratory
    • ORNL, Oak Ridge, TN, USA
    • Oak Ridge National Laboratory
    • Oak Ridge National Lab
    • Center for Nanophase Materials Sciences, Oak Ridge National Laboratory
    • Center for Nanophase Materials Sciences, ORNL

  • Haixuan Xu

    • Department of Materials Science and Engineering, The University of Tennessee
    • Department of Materials Science and Engineering, The University of Tennessee, Knoxville

  • Paul Kent

    • CNMS and CSMD, Oak Ridge National Laboratory
    • Oak Ridge National Laboratory
    • Computer Science and Mathematics Division; Center for Nanophase Materials Sciences, ORNL
    • Oak Ridge National Lab
    • Center for Nanophase Materials Sciences, Oak Ridge National Laboratory