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arXiv · 2101.01413

Observation of unconventional six-fold, four-fold and three-fold excitations in rare-earth-metal carbide Re2C3

Lei Jin·Ying Liu·Xiaoming Zhang·Xuefang Dai·Guodong Liu
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Abstract

Unconventional fermions, such as three-fold, four-fold, six-fold, and eight-fold fermions have attracted intense attention in recent years. However, the concrete materials hosting unconventional fermions are still in urgent scarcity. In this work, based first-principle calculations and symmetry analysis, we reveal rich unconventional fermions in existing compound Re2C3 (Re = Y, La, Ce, Pr, Nd, Sm, Tb, Dy, Ho, Er, Tm, Yb, Lu). We show that these compounds host quadratic dispersive three-fold (TP), linear dispersive four-fold (FP) and six-fold points (SP) near the Fermi level in their electric band structures when spin-orbital coupling (SOC) is not included. Notably, the FP is charge-2 Dirac-like point. More importantly, among compound Re2C3, the compound Yb2C3 has very clean band structure, and its unconventional fermions are closed to the Fermi level. We also find that a uniaxial strain can transform the unconventional fermions into other types fermions, depending on the directions of strain. When SOC is considered, a SP transform to an eightfold degenerate point and a fourfold degenerate point. Overall, our work provides a family of realistic materials to study the unconventional fermions.

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Lei Jin, Ying Liu, Xiaoming Zhang, Xuefang Dai, Guodong Liu. 2021-01-05. Observation of unconventional six-fold, four-fold and three-fold excitations in rare-earth-metal carbide Re2C3. https://arxiv.org/abs/2101.01413

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