Discovery of a Weyl fermion state with Fermi arcs in niobium arsenide

By Su-Yang Xu, N. Alidoust, I. Belopolski, Zhujun Yuan, G. Bian, Tay-Rong Chang, Hao Zheng, V. Strocov, D. Sanchez, G. Chang and 14 more. Nature Physics, 2015

785 citations recorded by the source corpus.

Three types of fermions play a fundamental role in our understanding of nature: Dirac, Majorana and Weyl. Whereas Dirac fermions have been known for decades, the latter two have not been observed as any fundamental particle in high-energy physics, and have emerged as a much-sought-out treasure in condensed matter physics. A Weyl semimetal is a novel crystal whose low-energy electronic excitations behave as Weyl fermions. It has received worldwide interest and is believed to open the next era of condensed matter physics after graphene and three-dimensional topological insulators. However, experimental research has been held back because Weyl semimetals are extremely rare in nature. Here, we present the experimental discovery of the Weyl semimetal state in an inversion-symmetry-breaking single-crystalline solid, niobium arsenide (NbAs). Utilizing the combination of soft X-ray and ultraviolet photoemission spectroscopy, we systematically study both the surface and bulk electronic structure of NbAs. We experimentally observe both the Weyl cones in the bulk and the Fermi arcs on the surface of this system. Our ARPES data, in agreement with our theoretical band structure calculations, identify the Weyl semimetal state in NbAs, which provides a real platform to test the potential of Weyltronics. Experiments show that niobium arsenide is a Weyl semimetal.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/742d7a57dcc56170e79cb5b83d7ef98a21605e2c

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Citations in the corpus

Topological Semimetals from First Principles (2018, background): “A decisive advance came in 2015, when the observation of a T -invariant Weyl semimetal phase was reported in TaAs and related materials (94, 95, 96, 97, 98, 99) based on earlier theoretical predictions (7, 33).”
Heusler 4.0: Tunable Materials (2016, background): “Weyl semimetals (WSM) are a class of topological semimetals, beyond topological insulators, where the conduction and valence bands cross in the vicinity of the Fermi level (88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100).”
Angle-resolved photoemission studies of quantum materials (2020, neutral): “We note that while topological surface states have been observed in Dirac semimetals (Xu et al., 2015e; Yi et al., 2015a), they do not enjoy the same level of protection as in Weyl semimetals due to the fact that the surfaces can break the spatial symmetries that preserve the crossings in the bulk…”
Topological semimetals with helicoid surface states (2015, neutral): “[37] Su-Yang Xu, Nasser Alidoust, Ilya Belopolski, Zhu-”
Weyl and Dirac semimetals in three-dimensional solids (2017, methodology): “One can see the role of electronegativity difference for instance in a comparison between Na3Sb and Na3Bi.”