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arXiv · 1304.5948

Evolution of the SrTiO$_3$ surface electronic state as a function of LaAlO$_3$ overlayer thickness

N. C. Plumb·M. Kobayashi·M. Salluzzo·E. Razzoli·C. Matt·V. N. Strocov·K. -J. Zhou·C. Monney·T. Schmitt·M. Shi·J. Mesot·L. Patthey·M. Radovic
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Abstract

The novel electronic properties emerging at interfaces between transition metal oxides, and in particular the discovery of conductivity in heterostructures composed of LaAlO$_3$ (LAO) and SrTiO$_3$ (STO) band insulators, have generated new challenges and opportunities in condensed matter physics. Although the interface conductivity is stabilized when LAO matches or exceeds a critical thickness of 4 unit cells (u.c.), other phenomena such as a universal metallic state found on the bare surface of STO single crystals and persistent photon-triggered conductivity in otherwise insulating STO-based interfaces raise important questions about the role of the LAO overlayer and the possible relations between vacuum/STO and LAO/STO interfaces. Here, we study how the metallic STO surface state evolves using angle-resolved photoemission spectroscopy (ARPES) in situ prepared samples complemented by resonant inelastic X-ray scattering (RIXS) during the growth of a crystalline LAO overlayer. In all the studied samples, the character of the conduction bands, their carrier densities, the Ti3+ crystal field, and the response to photon irradiation bear strong similarities. Nevertheless, we report here that studied LAO/STO interfaces exhibit an instability toward an apparent 2 x 1 folding of the Fermi surface at and above 4 u.c. thickness threshold, which distinguishes these heterostructures from bare STO and sub-critical-thickness LAO/STO.

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N. C. Plumb, M. Kobayashi, M. Salluzzo, E. Razzoli, C. Matt, V. N. Strocov, K. -J. Zhou, C. Monney, T. Schmitt, M. Shi, J. Mesot, L. Patthey, M. Radovic. 2013-04-22. Evolution of the SrTiO$_3$ surface electronic state as a function of LaAlO$_3$ overlayer thickness. https://doi.org/10.1016/j.apsusc.2017.03.208

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