Universal Approach to Magnetic Second-Order Topological Insulator

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Physics

Background:

• Topological insulators (TIs) exhibit unique electronic properties protected by topology.
• Second-order topological insulators (SOTIs) possess topologically protected states at lower-dimensional boundaries (e.g., corners).
• Realizing magnetic SOTIs is crucial for exploring novel quantum phenomena and spintronic applications.

Purpose of the Study:

• To propose a universal and practical approach for realizing magnetic SOTIs.
• To identify realistic material candidates for 2D magnetic SOTIs.
• To investigate the properties and experimental accessibility of protected states in magnetic SOTIs.

Main Methods:

• Theoretical approach based on breaking time-reversal symmetry in conventional TIs.
• First-principles calculations to predict and analyze material properties.
• Investigation of spin-orbit coupling and magnetic proximity effects.

Main Results:

• A practical strategy for creating magnetic SOTIs in both 2D and 3D is proposed.
• Bismuthene on EuO(111) is predicted as the first realistic 2D magnetic SOTI system.
• Protected corner states are demonstrated in a boundary gap of ~83 meV, experimentally accessible.

Conclusions:

• The proposed approach offers a viable route to engineer magnetic SOTIs.
• Bismuthene on EuO(111) serves as a promising platform for experimental studies of 2D magnetic SOTIs.
• Tunable topological phase transitions between 1st-order TI and SOTI phases are achievable in this system.