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Nat Commun. 2018 May 10;9(1):1854. doi: 10.1038/s41467-018-04080-4.

Chiral Landau levels in Weyl semimetal NbAs with multiple topological carriers.

Yuan X1,2, Yan Z3, Song C1,2, Zhang M4,5, Li Z5,6, Zhang C1,2, Liu Y1,2, Wang W1,2, Zhao M1,2, Lin Z1,2, Xie T1,2, Ludwig J7, Jiang Y7, Zhang X8, Shang C8, Ye Z1,2, Wang J1,2, Chen F1,2, Xia Z8, Smirnov D7, Chen X5,6, Wang Z3,6, Yan H9,10, Xiu F11,12,13.

Author information

1
State Key Laboratory of Surface Physics and Department of Physics, Fudan University, 200433, Shanghai, China.
2
Collaborative Innovation Center of Advanced Microstructures, Fudan University, 200433, Shanghai, China.
3
Institute for Advanced Study, Tsinghua University, 100084, Beijing, China.
4
International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China.
5
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, 100190, Beijing, China.
6
Collaborative Innovation Center of Quantum Matter, 100871, Beijing, China.
7
National High Magnetic Field Laboratory, Tallahassee, Florida, 32310, USA.
8
Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, 430074, Wuhan, China.
9
State Key Laboratory of Surface Physics and Department of Physics, Fudan University, 200433, Shanghai, China. Hgyan@fudan.edu.cn.
10
Collaborative Innovation Center of Advanced Microstructures, Fudan University, 200433, Shanghai, China. Hgyan@fudan.edu.cn.
11
State Key Laboratory of Surface Physics and Department of Physics, Fudan University, 200433, Shanghai, China. Faxian@fudan.edu.cn.
12
Collaborative Innovation Center of Advanced Microstructures, Fudan University, 200433, Shanghai, China. Faxian@fudan.edu.cn.
13
Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, 200433, Shanghai, China. Faxian@fudan.edu.cn.

Abstract

Recently, Weyl semimetals have been experimentally discovered in both inversion-symmetry-breaking and time-reversal-symmetry-breaking crystals. The non-trivial topology in Weyl semimetals can manifest itself with exotic phenomena, which have been extensively investigated by photoemission and transport measurements. Despite the numerous experimental efforts on Fermi arcs and chiral anomaly, the existence of unconventional zeroth Landau levels, as a unique hallmark of Weyl fermions, which is highly related to chiral anomaly, remains elusive owing to the stringent experimental requirements. Here, we report the magneto-optical study of Landau quantization in Weyl semimetal NbAs. High magnetic fields drive the system toward the quantum limit, which leads to the observation of zeroth chiral Landau levels in two inequivalent Weyl nodes. As compared to other Landau levels, the zeroth chiral Landau level exhibits a distinct linear dispersion in magnetic field direction and allows the optical transitions without the limitation of zero z momentum or [Formula: see text] magnetic field evolution. The magnetic field dependence of the zeroth Landau levels further verifies the predicted particle-hole asymmetry of the Weyl cones. Meanwhile, the optical transitions from the normal Landau levels exhibit the coexistence of multiple carriers including an unexpected massive Dirac fermion, pointing to a more complex topological nature in inversion-symmetry-breaking Weyl semimetals. Our results provide insights into the Landau quantization of Weyl fermions and demonstrate an effective tool for studying complex topological systems.

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