5 years ago

Magnetic-tunnelling-induced Weyl node annihilation in TaP

Magnetic-tunnelling-induced Weyl node annihilation in TaP
Jinglei Zhang, Chi-Cheng Lee, Hsin Lin, Shuang Jia, Hai-Zhou Lu, Guoqing Chang, Z. Z. Du, Cheng-Long Zhang, Xin-Cheng Xie, Shin-Ming Huang, Su-Yang Xu, M. Zahid Hasan, Titus Neupert, Chi Zhang, Haiwen Liu, Ziquan Lin, Yiyang Feng, Hong Lu, Junfeng Wang, Chuang-Han Hsu, Cheng Guo, Liang Li, C. M. Wang
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 (1/2planckω), 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.

Publisher URL: http://dx.doi.org/10.1038/nphys4183

DOI: 10.1038/nphys4183

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