Orientation-dependent electronic structure in interfacial superconductors LaAlO₃/KTaO₃

Area of Science:

• Condensed Matter Physics
• Materials Science
• Oxide Interfaces

Background:

• Emergent superconductivity at oxide interfaces like LaAlO3/KTaO3 is sensitive to crystallographic orientation.
• The underlying mechanisms for this orientation dependence remain poorly understood.

Purpose of the Study:

• To directly probe the electronic structure of superconducting and non-superconducting LaAlO3/KTaO3 interfaces.
• To elucidate the role of electronic properties and electron-phonon coupling in orientation-dependent superconductivity.

Main Methods:

• Soft X-ray Angle-Resolved Photoemission Spectroscopy (SX-ARPES) to resolve electronic structure.
• Analysis of electron dispersion (k⊥) and spatial distribution of the electron gas.
• Identification and quantification of electron-phonon coupling signatures.

Main Results:

• Mobile electrons contributing to superconductivity exhibit strong k⊥ dispersion.
• A quasi-3D electron gas with significant spatial distribution is present in both superconducting and non-superconducting interfaces.
• Electron-phonon coupling signatures are orientation-dependent and correlate positively with superconducting transition temperature (Tc).

Conclusions:

• The observed orientation-dependent electron-phonon coupling offers a straightforward explanation for varying Tc in LaAlO3/KTaO3 interfaces.
• The findings challenge existing theories and highlight the importance of interfacial engineering for oxide-based electronics.