Weyl fermions1,2,3 have been observed as three-dimensional, gapless topological excitations in weakly correlated, inversion-symmetry-breaking semimetals4,5. However, their realization in spontaneously time-reversal-symmetry-breaking phases of strongly correlated materials has so far remained hypothetical2,6,7. Here, we report experimental evidence for magnetic Weyl fermions in Mn3Sn, a non-collinear antiferromagnet that exhibits a large anomalous Hall effect, even at room temperature8. Detailed comparison between angle-resolved photoemission spectroscopy (ARPES) measurements and density functional theory (DFT) calculations reveals significant bandwidth renormalization and damping effects due to the strong correlation among Mn 3d electrons. Magnetotransport measurements provide strong evidence for the chiral anomaly of Weyl fermions—namely, the emergence of positive magnetoconductance only in the presence of parallel electric and magnetic fields. Since weak magnetic fields (approximately 10 mT) are adequate to control the distribution of Weyl points and the large fictitious fields (equivalent to approximately a few hundred T) produced by them in momentum space, our discovery lays the foundation for a new field of science and technology involving the magnetic Weyl excitations of strongly correlated electron systems such as Mn3Sn.
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This work was supported by CREST (JPMJCR15Q5), Japan Science and Technology Agency, Grants-in-Aid for Scientific Research (Grant Nos. 16H02209, 25707030), by Grants-in-Aid for Scientific Research on Innovative Areas ‘J-Physics’ (Grant Nos. 15H05882 and 15H05883), and ‘Topological Materials Science’ (Grant No. 16H00979), and Grants-in-Aid for Young Scientists A (Grants No. 16H06013) and B (Grants No. 17K14319), and Grant-in-Aid for Exploratory Research (Grants No. 16K13829), and Program for Advancing Strategic International Networks to Accelerate the Circulation of Talented Researchers (Grant No. R2604) from the Japanese Society for the Promotion of Science, and Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan. P.G. was supported by JQI-NSF-PFC and LPS-MPO-CMTC. The use of the facilities of the Materials Design and Characterization Laboratory at the Institute for Solid State Physics, The University of Tokyo, is gratefully acknowledged. We thank S. Kunisada, M. Sakano and E. Golias for technical supports to perform ARPES measurements. The soft X-ray synchrotron radiation experiments were performed with the approval of JASRI (Proposal Nos. 2015B2002, 2016A1296, 2016B1262). The vacuum ultraviolet experiments were performed under the approval of the Photon Factory Program Advisory Committee (Proposal No. 2016G622). We thank Helmholtz-Zentrum Berlin (HZB) for the allocation of synchrotron radiation beam time.