Electronic properties of LaAlO₃/SrTiO₃ n-type interfaces: a GGA+U study

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Chemistry

Background:

• Realistic electronic property descriptions of heterostructures require accounting for electronic correlation effects.
• The GGA+U approach is commonly used to model these effects, particularly on-site Coulomb repulsion.

Purpose of the Study:

• Investigate the role of electronic correlation effects in LaAlO3/SrTiO3 heterostructures.
• Systematically study the impact of Coulomb parameters on Ti 3d and La 4f orbitals.
• Provide deeper insight into the band gap landscape and interference effects.

Main Methods:

• Employed the GGA+U approach to model electronic correlation effects.
• Performed systematic variations of Coulomb parameters for Ti 3d and La 4f orbitals.
• Analyzed the resulting band gap landscape and atomic displacements.

Main Results:

• Identified significant correlations between local Coulomb interaction (La 4f), band gap, and atomic displacements.
• Demonstrated that on-site Coulomb interactions influence LaO interface buckling.
• Showed that interface buckling affects electrostatic potential, leading to electronic state shifts and band gap control.

Conclusions:

• The on-site Coulomb interaction, particularly for La 4f orbitals, is a critical factor in determining the electronic properties of LaAlO3/SrTiO3 heterostructures.
• Atomic displacements at the interface, driven by Coulomb interactions, play a key role in controlling the band gap.
• Previous suggestions for large La 4f Coulomb parameters require re-evaluation in light of these findings.