# High sensitivity variable-temperature infrared nanoscopy of conducting oxide interfaces

## TL;DR

This study demonstrates that scattering-type near-field optical microscopy can non-invasively and with high spatial resolution probe the local transport properties of conducting oxide interfaces over a wide temperature range, revealing detailed electronic behavior.

## Contribution

The paper introduces a novel application of near-field optical microscopy for quantitative, high-resolution analysis of 2D electron systems at buried oxide interfaces across broad temperatures.

## Key findings

- Near-field optical phase is highly sensitive to 2DES transport properties.
- Modeling links optical signals to plasmon-phonon interactions and electron transport.
- Spatial imaging of nano-channels demonstrates technique's resolution and applicability.

## 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.