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

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.

References in corpus (21)

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• Nature of weak magnetism in SrTiO3/LaAlO3 multilayers
• Hard x-ray photoemission and density functional theory study of the internal electric field in SrTiO3/LaAlO3 oxide heterostructures
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• Electrical properties of improper ferroelectrics from first principles
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• Reversible and Persistent Photoconductivity at the NdGaO3/SrTiO3 Conducting Interface

Cited by in corpus (10)

• Origin of two-dimensional electron gases at oxide interfaces: insights from theory
• Two-dimensional electron systems in perovskite oxide heterostructures: Role of the polarity-induced substitutional defects
• Artificial quantum confinement in LAO3/STO heterostructure
• Soft x-ray irradiation induced metallization of layered TiNCl
• A Laser-ARPES View of the 2D Electron Systems at LaAlO3/SrTiO3 and Al/SrTiO3 Interfaces
• Polarity-field driven conductivity in SrTiO${}_3$/LaAlO${}_3$: a hybrid functional study
• Probing the polar-nonpolar oxide interfaces using resonant x-ray standing wave techniques
• Metal to insulator transition at the surface of $V_2{O}_3$ thin films: an in-situ view
• Hidden antiferromagnetism on the light-irradiated surface of bulk SrTiO3 and at the LaAlO3_SrTiO3 interfaces
• A two-dimensional electron gas at the (001) surface of ferromagnetic EuTiO${}_3$(001)