论文标题

EUCD $ _2 $的自旋结构中的单对Weyl节点为$ _2 $

Single pair of Weyl nodes in the spin-canted structure of EuCd$_2$As$_2$

论文作者

Taddei, K. M., Yin, L., Sanjeewa, L. D., Li, Y., Xing, J., Cruz, C. dela, Phelan, D., Sefat, A. S., Parker, D.

论文摘要

在Weyl材料中,时间逆转对称性破坏Weyl半法是独特的,在允许的Weyl点数量最少,从而提供了相关物理的最明显特征。在这里,我们提出中子衍射,密度功能理论和传输测量结果,表明在环境场,应变和压力下,EUCD $ _2 $为$ _2 $,是一种具有单对Weyl点的材料。我们的工作揭示了一个磁性结构(磁性空间$ c2'/m'$),欧盟瞬间指向[210]方向的平面内和倾斜的$ \ sim $ 30 $^{\ circ} $脱机。使用该结构的密度功能理论计算表明,相对于平面内顺序,观察到的倾斜大大改变了相关的电子带,从而导致一组定义良好的Weyl点。此外,我们发现倾斜角可以调整韦尔点在费米水平上方的距离,而低倾斜角的距离最小。最后,对异常霍尔效应和纵向磁化的转运测量表明特性表明了手性异常,因此支持中子散射和DFT结果,表明EUCD $ _2 $,因为$ _2 $接近Weyl“ hydogen otogen” hydogogen otogen Atom的理想情况。

Time reversal symmetry breaking Weyl semimetals are unique among Weyl materials in allowing the minimal number of Weyl points thus offering the clearest signatures of the associated physics. Here we present neutron diffraction, density functional theory and transport measurement results which indicate that EuCd$_2$As$_2$ , under ambient field, strain and pressure, is such a material with a single pair of Weyl points. Our work reveals a magnetic structure (magnetic space group $C2'/m'$) with Eu moments pointing along the [210] direction in-plane and canted $\sim$ 30$^{\circ}$ out-of-plane. Density functional theory calculations using this structure show that the observed canting drastically alters the relevant electronic bands, relative to the in-plane order, leading to a single set of well defined Weyl points. Furthermore, we find the canting angle can tune the distance of the Weyl points above the Fermi level, with the smallest distance at low canting angles. Finally, transport measurements of the anomalous Hall Effect and longitudinal magnetoresistance exhibit properties indicative of a chiral anomaly, thus supporting the neutron scattering and DFT results suggesting EuCd$_2$As$_2$ is close to the ideal situation of the Weyl "Hydrogen atom".

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