Weyl nodes are topological objects in three-dimensional metals. Whereas the energy of the lowest Landau band of a conventional Fermi pocket increases with magnetic field due to the zero-point energy (1/2ℏω), the lowest Landau band of Weyl cones stays at zero energy unless a strong magnetic field couples Weyl fermions of opposite chirality. In the Weyl semimetal TaP, which possesses two types of Weyl nodes (four pairs of W1 and eight pairs of W2 nodes), we observed such a magnetic coupling between the electron pockets arising from the W1 Weyl fermions. As a result, their lowest Landau bands move above the chemical potential, leading to a sharp sign reversal in the Hall resistivity at a specific magnetic field corresponding to the separation in momentum space of the W1 Weyl nodes, . By contrast, annihilation is not observed for the hole pocket because the separation of the W2 Weyl nodes is much larger. These findings reveal the nontrivial topology of Weyl fermions in high-field transport measurements and demonstrate the observation of Weyl node annihilation, which is a unique topological phenomenon associated with Weyl fermions.

Weyl节点是三维金属中的拓扑对象。而与磁场由于零点能常规费米口袋增加（1/2最低兰道带的能量ℏ ω），外尔的最低朗道带在零能量锥体停留除非强磁场耦合外尔具有相反手性的费米子。在拥有两种类型的Weyl节点（四对W1和八对W2节点）的Weyl半金属TaP中，我们观察到了由W1 Weyl费米子引起的电子腔之间的这种磁耦合。结果，它们的最低Landau能带移动到化学势之上，导致在对应于W1 Weyl节点动量空间分离的特定磁场下，霍尔电阻率出现急剧的符号反转，。相比之下，由于W2 Weyl节点的间距大得多，因此没有观察到空穴消失的现象。这些发现揭示了高场输运测量中Weyl费米子的非平凡拓扑结构，并证明了Weyl节点an灭的观察，这是与Weyl费米子有关的独特拓扑现象。