Abstract Topological semimetals with hosting multiple types of fermions has attracted considerable attention currently. For such materials, however, the signatures for different fermions such as the nontrivial surface states are usually tangled together, which troubles their experimental detections. Here, by using the first-principles calculation, we propose that the CsCl-type compound ErAs host multiple fermionic states near the Fermi level. Most importantly, all these fermionic states can exhibit clear surface signature. When spin–orbit coupling (SOC) is not included, ErAs totally shows three pairs of triply degenerate nodal points (TDNPs) and six nodal lines. Especially, three of the nodal lines host both type-I and type-II band crossings, namely hybrid nodal lines. The TDNPs and nodal lines in ErAs are characterized with clear Fermi arcs and drumhead surface states. After considering SOC, it emerges three pairs of Dirac points in ErAs. These Dirac points can also show clear Fermi arc surface states, which strongly favors their experimental detections.

中文翻译：

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在 CsCl 型化合物 ErAs 中具有清晰非平凡表面特征的多个费米子态

摘要 目前，承载多种费米子的拓扑半金属引起了广泛关注。然而，对于此类材料，不同费米子的特征（例如非平凡的表面态）通常会纠缠在一起，这给它们的实验检测带来了麻烦。在这里，通过使用第一性原理计算，我们提出 CsCl 型化合物 ErAs 在费米能级附近拥有多个费米子态。最重要的是，所有这些费米子态都可以表现出清晰的表面特征。当不包括自旋轨道耦合 (SOC) 时，ErAs 总共显示三对三重简并节点 (TDNP) 和六个节点线。特别是，其中三个节点线同时包含 I 型和 II 型带交叉，即混合节点线。ErA 中的 TDNP 和节点线具有清晰的费米弧和鼓面表面状态。在考虑 SOC 后，在 ErAs 中出现了三对 Dirac 点。这些狄拉克点还可以显示清晰的费米弧表面状态，这对他们的实验检测非常有利。