Mapping spin-charge conversion to the band structure in a topological oxide two-dimensional electron gas

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Traditional spintronics uses ferromagnetic metals.
• Spin-orbitronics leverages spin-orbit coupling in non-magnetic systems for spin-charge conversion.
• The standard Rashba model inadequately explains large conversion effects and their electronic structure origins.

Purpose of the Study:

• To demonstrate and characterize a significant spin-to-charge conversion effect in an engineered strontium titanate (SrTiO3) two-dimensional electron gas (2DEG).
• To investigate the relationship between this conversion effect and the material's band structure under gate modulation.
• To explore the role of orbital mixing and topological properties in enhancing spin-charge conversion.

Main Methods:

• Fabrication of an interface-engineered, high-carrier-density SrTiO3 2DEG.
• Experimental measurement of spin-to-charge conversion efficiency.
• Gate-dependent characterization of the electronic band structure.
• Theoretical analysis linking conversion effects to band structure features like orbital mixing and avoided band crossings.

Main Results:

• Observation of a very large spin-to-charge conversion effect in the SrTiO3 2DEG.
• Demonstration that conversion efficiency is gate-tunable and strongly correlated with the band structure.
• Identification of enhanced Rashba-like splitting from orbital mixing and topologically non-trivial band crossings as key amplification mechanisms.

Conclusions:

• Oxide 2DEGs, specifically SrTiO3, exhibit significant spin-to-charge conversion, making them promising for spin-based information readout in novel memory and transistor devices.
• Topological properties and orbital mixing are crucial for maximizing spin-charge conversion efficiency in spintronics.
• This work highlights the potential of complex oxides and topology in advancing spintronic applications.