Stability of Weyl node merging processes under symmetry constraints

Abstract

Changes in the number of Weyl nodes in Weyl semimetals occur through merging processes, usually involving a pair of oppositely charged nodes. More complicated processes involving multiple Weyl nodes are also possible, but they typically require fine tuning and are thus less stable. In this work, we study how symmetries affect the allowed merging processes and their stability, focusing on the combination of a two-fold rotation and time-reversal ($C_2\mathcal{T}$) symmetry. We find that, counter-intuitively, processes involving a merging of three nodes are more generic than processes involving only two nodes. Our work suggests that multi-Weyl-merging may be observed in a large variety of quantum materials, and we discuss SrSi${}_2$ and bilayer graphene as potential candidates

References in corpus (7)

• Unconventional quantum Hall effect and Berry's phase of 2pi in bilayer graphene
• Phase transition between the quantum spin Hall and insulator phases in 3D: emergence of a topological gapless phase
• The electronic properties of bilayer graphene
• Topological nodal line semimetals
• Weyl semimetals from noncentrosymmetric topological insulators
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Cited by in corpus (3)

• Symmetry-adapted models for multifold fermions with spin-orbit coupling
• Optical conductivity and band gap in the double-Weyl candidate SrSi2 at ambient pressure
• The geometry of the Hermitian matrix space and the Schrieffer--Wolff transformation