Realization of Practical Eightfold Fermions and Fourfold van Hove Singularity in TaCo$_2$Te$_2$
Abstract
Space groups describing the symmetry of lattice structure allow the emergence of fermionic quasiparticles with various degeneracy in the band structure. Theoretical efforts have predicted many materials hosting fermions with the highest degeneracy, i.e., eightfold fermions, yet lacking experimental realization. Here, we explore the band degeneracies in TaCoTe crystals. Through systematic experimental and theoretical analyses, we establish TaCoTe as a nonsymmorphic crystal with negligible spin-orbit coupling (SOC) and long-range magnetic order. These critical properties guarantee the first realization of practical eightfold fermions and fourfold van Hove singularity, as directly observed by photoemission spectroscopy. TaCoTe serves as a topological quantum critical platform, which can be tuned into various magnetic, topologically trivial, and nontrivial phases by adding strain, magnetic field, or SOC. The latter is demonstrated by our first-principles calculations, which show that enhancing SOC in TaCoTe will promote the experimental observation of bulk hourglass fermions. Our results establish TaCoTe as a unique platform to explore states of matter intertwining magnetism, correlation, symmetry, and band topology.
Keywords
Cite
@article{arxiv.2208.02967,
title = {Realization of Practical Eightfold Fermions and Fourfold van Hove Singularity in TaCo$_2$Te$_2$},
author = {Hongtao Rong and Zhenqiao Huang and Xin Zhang and Shiv Kumar and Fayuang Zhang and Chengcheng Zhang and Yuan Wang and Zhanyang Hao and Yongqing Cai and Le Wang and Cai Liu and Xiao-Ming Ma and Shu Guo and Bing Shen and Yi Liu and Shengtao Cui and Kenya Shimada and Quansheng Wu and Junhao Lin and Yugui Yao and Zhiwei Wang and Hu Xu and Chaoyu Chen},
journal= {arXiv preprint arXiv:2208.02967},
year = {2024}
}