Topological nodal lines and hybrid Weyl nodes in YCoC$_2$
Abstract
Based on first-principles calculations and effective model analysis, we propose that the noncentrosymmetric superconductor YCoC in normal state is a topological semimetal. In the absence of spin-orbit coupling (SOC), it can host two intersecting nodal rings protected by two mirror planes, respectively. One ring is composed of type-I nodes, where the two crossing bands have opposite slop sign in their dispersions. The other ring consists of both type-I and type-II nodes (the slop signs of the two bands are the same in certain direction). In the presence of SOC, the former nodal ring is gapped totally while the later one evolves into ten pairs of Weyl nodes, with two of them being type-I and eight being type-II. The type-II Weyl nodes are further classified into two kinds with different velocity matrix when described in Weyl equation near the nodes. Fermi arcs from topological surface states are observed in the surface projected energy dispersions. It is notably that YCoC has been reported as a superconductor with critical temperature of 4.2 K. This makes it very attractive since including superconducting into topological semimetal state might result in topological superconductivity and be used to synthesize Majorana zero modes.
Keywords
Cite
@article{arxiv.1905.01757,
title = {Topological nodal lines and hybrid Weyl nodes in YCoC$_2$},
author = {Yuanfeng Xu and Yueqiang Gu and Tiantian Zhang and Chen Fang and Zhong Fang and Xianlei Sheng and Hongming Weng},
journal= {arXiv preprint arXiv:1905.01757},
year = {2019}
}