Direct imaging of the electron liquid at oxide interfaces

Area of Science:

• Condensed Matter Physics
• Materials Science
• Surface Science

Background:

• Symmetry breaking in oxide heterostructures leads to interfacial orbital reconstruction.
• Orbital reconstruction influences electron confinement and properties at interfaces.
• LaAlO3/SrTiO3 interfaces host two-dimensional electron liquids with varying properties.

Purpose of the Study:

• To investigate the impact of crystal symmetry on electron confinement at oxide interfaces.
• To resolve the spatial distribution and quantum confinement of interfacial electrons.
• To compare electron behavior at (001) and (111) LaAlO3/SrTiO3 interfaces.

Main Methods:

• Utilizing inline electron holography for sub-nanometer resolution imaging.
• Analyzing charge density maps of two-dimensional electron liquids.
• Comparing experimental results with density functional theory calculations.

Main Results:

• Demonstrated selective orbital occupation and spatial quantum confinement of electrons.
• Observed narrow electron confinement (~1.0 nm) at the (001) interface.
• Revealed broader electron confinement (~3.3 nm) with density maximum away from the interface at the (111) interface.

Conclusions:

• Inline electron holography effectively visualizes electron behavior at oxide interfaces.
• Crystal symmetry significantly dictates the spatial extent of two-dimensional electron liquids.
• Findings align with theoretical predictions, validating the experimental approach.