High sensitivity variable-temperature infrared nanoscopy of conducting oxide interfaces

Abstract

Probing the local transport properties of two-dimensional electron systems (2DES) confined at buried interfaces requires a non-invasive technique with a high spatial resolution operating in a broad temperature range. In this paper, we investigate the scattering-type scanning near field optical microscopy as a tool for studying the conducting LaAlO3/SrTiO3 interface from room temperature down to 6 K. We show that the near-field optical signal, in particular its phase component, is highly sensitive to the transport properties of the electron system present at the interface. Our modelling reveals that such sensitivity originates from the interaction of the AFM tip with coupled plasmon-phonon modes with a small penetration depth. The model allows us to quantitatively correlate changes in the optical signal with the variation of the 2DES transport properties induced by cooling and by electrostatic gating. To probe the spatial resolution of the technique, we image conducting nano-channels written in insulating heterostructures with a voltage-biased tip of an atomic force microscope.

19 pages, 5 figures

References in corpus (6)

• Electric Field Control of the LaAlO${}_3$/SrTiO${}_3$ Interface Ground State
• Highly confined low-loss plasmons in graphene-boron nitride heterostructures
• Highly efficient and tuneable spin-to-charge conversion through Rashba coupling at oxide interfaces
• Electron-phonon interaction and charge carrier mass enhancement in SrTiO3
• Intrinsic instability of electronic interfaces with strong Rashba coupling
• Direct Imaging of Sketched Conductive Nanostructures at the LaAlO3/SrTiO3 Interface