In materials chiral fermions such as Weyl fermions are characterized by nonzero chiral charges, which are singular points of Berry curvature in momentum space. Recently, new types of chiral fermions beyond Weyl fermions have been discovered in structurally chiral crystals CoSi, RhSi and PtAl. Here, we have synthesized RhSn single crystals, which have opposite structural chirality to the CoSi crystals we previously studied. Using angle-resolved photoemission spectroscopy, we show that the bulk electronic structures of RhSn are consistent with the band calculations and observe evident surface Fermi arcs and helical surface bands, confirming the existence of chiral fermions in RhSn. It is noteworthy that the helical surface bands of the RhSn and CoSi crystals have opposite handedness, meaning that the chiral fermions are reversed in the crystals of opposite structural chirality. Our discovery establishes a direct connection between chiral fermions in momentum space and chiral lattices in real space.
@article{arxiv.1912.02383,
title = {Chiral fermion reversal in chiral crystals},
author = {Hang Li and Sheng Xu and Zhi-Cheng Rao and Li-Qin Zhou and Zhi-Jun Wang and Shi-Ming Zhou and Shang-Jie Tian and Shun-Ye Gao and Jia-Jun Li and Yao-Bo Huang and He-Chang Lei and Hong-Ming Weng and Yu-Jie Sun and Tian-Long Xia and Tian Qian and Hong Ding},
journal= {arXiv preprint arXiv:1912.02383},
year = {2019}
}