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

Abstract

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 $C{2}^{\prime }/m^{\prime }$) 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".

8 pages, 4 figures

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• EuCd${}_2$As${}_2$: a magnetic semiconductor
• Intrinsic Magnetic Topological Materials
• Spin-carrier coupling induced ferromagnetism and giant resistivity peak in EuCd${}_2$P${}_2$
• Topological Hall Effect Driven by Short-Range Magnetic Orders in EuZn${}_2$As${}_2$
• The discovery of three-dimensional Van Hove singularity
• Carrier-induced transition from antiferromagnetic insulator to ferromagnetic metal in the layered phosphide EuZn${}_2$P${}_2$
• Absence of Weyl nodes in EuCd${}_2$As${}_2$ revealed by the carrier density dependence of the anomalous Hall effect
• Influence of magnetism, strain and pressure on the band topology of EuCd${}_2$As${}_2$
• Absence of metallicity and bias-dependent resistivity in low-carrier-density EuCd2As2
• Recent advances in understanding and manipulating magnetic and electronic properties of Eu$M_2{X}_2$ ($M$ = Zn, Cd; $X$ = P, As)
• Spectroscopic signatures of magnetization-induced band renormalization and strong spin-charge-lattice coupling in EuZn${}_2$As${}_2$
• Electronic Transport and Fermi Surface Topology of Zintl Phase Compound SrZn2Ge2
• Structural and magnetic properties of CoTeMoO${}_6$ revisited
• Temperature Dependent Evolution of the Electronic Structure in EuZn2As2 across the Neel Transition