Magnetic Semimetals and Quantized Anomalous Hall Effect in EuB_{6}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• The interplay between magnetic order and topological properties in materials is a frontier in condensed matter physics.
• Topological semimetals exhibit unique electronic band structures with significant potential for advanced electronic applications.

Purpose of the Study:

• To predict and characterize novel topological semimetal phases in the ferromagnetic material Europium Hexaboride (EuB$_{6}$).
• To investigate the tunability of topological phases by controlling magnetic ordering direction.

Main Methods:

• First-principles electronic structure calculations.
• Analysis of magnetic moment orientation effects on band topology.
• Computation of topological surface states and anomalous Hall conductivity.

Main Results:

• EuB$_{6}$ transitions to a topological nodal-line semimetal with [001] magnetic moment alignment.
• Rotation to [111] alignment induces a Weyl semimetal phase with three Weyl point pairs.
• A composite phase with coexisting nodal lines and Weyl points is predicted for [110] alignment.

Conclusions:

• Magnetic moment orientation in EuB$_{6}$ offers a powerful knob to control and realize diverse topological semimetal phases.
• Predicted topological surface states and anomalous Hall conductivity are experimentally verifiable.
• Potential for realizing a large-Chern-number quantum anomalous Hall effect in [111]-oriented quantum wells.