Symmetry-protected triplet Weyl complexes
Abstract
The Nielsen-Ninomiya theorem dictates that Weyl nodes must appear in pairs of opposite chirality to preserve global charge neutrality. However, in crystals, specific crystalline symmetries can stabilize multi-Weyl nodes, circumventing this pairwise constraint and enabling compensated Weyl complexes with mixed chiral charges. The minimal configuration of this type is a triplet Weyl complex (TWC), comprising exactly three Weyl nodes. Here, we systematically investigate the symmetry conditions required to realize TWCs. By screening all 1651 magnetic space groups (MSGs) in both spinless and spinful systems, we establish that: (i) Only TWCs with charge magnitudes of {1,1,2} and {1,2,3} are permitted; (ii) the {1,1,2} configuration can be realized in 166 spinless MSGs and 70 spinful MSGs; and (iii) the {1,2,3}-TWCs, which has not been reported before, can occur in 10 MSGs for both spinless and spinful cases. We explicitly demonstrate the existence of {1,2,3}-TWC in a tight-binding model. Furthermore, we present the first electronic realization of {1,1,2}-TWC topological semimetal state in the chiral carbon allotrope DZQH-C36, in which the three Weyl nodes form a collinear configuration, leading to a characteristic ``S''-shaped surface Fermi arc pattern. Our findings uncover novel topological states featuring mixed chiral charges and provide guidance for exploring their physics in concrete material systems.
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BibTeX
@misc{bai2026symmetryprotected,
title = {{Symmetry-protected triplet Weyl complexes}},
author = {Yun-Yun Bai and Ke-Xin Pang and Yan Gao and Weikang Wu and Shengyuan A. Yang},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.05120},
eprint = {2609.05120},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.05120},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Symmetry-protected triplet Weyl complexes
AU - Yun-Yun Bai
AU - Ke-Xin Pang
AU - Yan Gao
AU - Weikang Wu
AU - Shengyuan A. Yang
PY - 2026
DA - 2026/09/04
PB - arXiv
DO - 10.48550/arxiv.2609.05120
UR - https://arxiv.org/abs/2609.05120
AB - The Nielsen-Ninomiya theorem dictates that Weyl nodes must appear in pairs of opposite chirality to preserve global charge neutrality. However, in crystals, specific crystalline symmetries can stabilize multi-Weyl nodes, circumventing this pairwise constraint and enabling compensated Weyl complexes with mixed chiral charges. The minimal configuration of this type is a triplet Weyl complex (TWC), comprising exactly three Weyl nodes. Here, we systematically investigate the symmetry conditions required to realize TWCs. By screening all 1651 magnetic space groups (MSGs) in both spinless and spinful systems, we establish that: (i) Only TWCs with charge magnitudes of {1,1,2} and {1,2,3} are permitted; (ii) the {1,1,2} configuration can be realized in 166 spinless MSGs and 70 spinful MSGs; and (iii) the {1,2,3}-TWCs, which has not been reported before, can occur in 10 MSGs for both spinless and spinful cases. We explicitly demonstrate the existence of {1,2,3}-TWC in a tight-binding model. Furthermore, we present the first electronic realization of {1,1,2}-TWC topological semimetal state in the chiral carbon allotrope DZQH-C_36, in which the three Weyl nodes form a collinear configuration, leading to a characteristic ``S''-shaped surface Fermi arc pattern. Our findings uncover novel topological states featuring mixed chiral charges and provide guidance for exploring their physics in concrete material systems.
ER -