Stability of Weyl Node Merging Processes under Symmetry Constraints.

Area of Science:

• Condensed Matter Physics
• Quantum Materials
• Topological Materials

Background:

• Weyl semimetals host Weyl nodes, whose number changes via merging processes.
• Merging typically involves pairs of oppositely charged nodes, with complex multi-node mergers being less stable and requiring fine-tuning.

Purpose of the Study:

• To investigate the influence of symmetries on Weyl node merging processes and their stability.
• To focus on the combined effect of twofold rotation and time-reversal (C_{2}T) symmetry.

Main Methods:

• Theoretical analysis of symmetry constraints on Weyl node merging.
• Examination of multi-Weyl node merging processes.

Main Results:

• Symmetries, specifically C_{2}T, allow for more generic multi-Weyl node merging.
• Counterintuitively, three-node merging processes are found to be more generic than two-node merging.
• Stability of merging processes is directly linked to the involved symmetries.

Conclusions:

• Multi-Weyl node merging is not limited to fine-tuned scenarios and can be more generic under specific symmetries.
• Quantum materials like SrSi_{2} and bilayer graphene are potential candidates for observing multi-Weyl merging.
• The findings expand the understanding of topological phase transitions in quantum materials.