Quantum Anomalous Hall State in Ferromagnetic SrRuO_{3} (111) Bilayers

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid State Physics

Background:

• Strontium ruthenium oxide (SrRuO3) thin films are rare examples of (111)-oriented ferromagnets.
• Investigating the properties of SrRuO3 at reduced dimensions is crucial for understanding fundamental physics and potential applications.

Purpose of the Study:

• To investigate the stability of the ferromagnetic state in SrRuO3 heterostructures under dimensional confinement.
• To explore the emergence of novel electronic phases in ultrathin SrRuO3 films.

Main Methods:

• Utilizing density functional theory (DFT) combined with dynamical mean-field theory (DMFT).
• Simulating SrRuO3 heterostructures down to the bilayer limit.

Main Results:

• The half-metallic ferromagnetic state with an ordered magnetic moment of 2 μB/Ru is preserved down to the bilayer.
• This state remains stable even at elevated temperatures (500 K).
• Spin-orbit coupling opens a gap in the minority band, leading to a predicted quantum anomalous Hall state with Chern number C=1.

Conclusions:

• Ultrathin SrRuO3 films exhibit robust ferromagnetism and dimensional confinement effects.
• The predicted quantum anomalous Hall state emerges intrinsically, without external magnetic fields or impurities.
• These findings open avenues for exploring topological quantum phenomena in oxide heterostructures.