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arXiv · 1912.00346

Direct observation of six-fold exotic fermions in topological semimetal PdSb$_2$

Sun Zhipeng·Hua Chenqiang·Liu Xiaolei·Liu Zhengtai·Ye Mao·Qiao Shan·Liu Zhonghao·Liu Jishan·Guo Yanfeng·Lu Yunhao·Shen Dawei
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Abstract

Pyrite-type PdSb$_2$ with a nonsymmorphic cubic structure has been predicted to host six-fold-degenerate exotic fermions beyond the Dirac and Weyl fermions. Though magnetotransport measurements on PdSb$_2$ suggest its topologically nontrivial character, direct spectroscpic study of its band structure remains absent. Here, by utilizing high-resolution angle-resolved photoemission spectroscopy, we present a systematic study on its bulk and surface electronic structure. Through careful comparison with first-principles calculations, we verify the existence of six-fold fermions in PdSb$_2$, which are formed by three doubly degenerate bands centered at the $R$ point in the Brillouin zone. These bands exhibit parabolic dispersion close to six-fold fermion nodes, in sharp contrast to previously reported ones in chiral fermion materials. Furthermore, our data reveal no protected Fermi arcs in PdSb$_2$, which is compatible with its achiral structure. Our findings provide a remarkable platform for study of new topological fermions and indicate their potential applications.

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Sun Zhipeng, Hua Chenqiang, Liu Xiaolei, Liu Zhengtai, Ye Mao, Qiao Shan, Liu Zhonghao, Liu Jishan, Guo Yanfeng, Lu Yunhao, Shen Dawei. 2019-12-09. Direct observation of six-fold exotic fermions in topological semimetal PdSb$_2$. https://doi.org/10.1103/physrevb.101.155114

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