@article{685422eddb7d470e86861dba212f0f00,
title = "Anomalous spin correlations and excitonic instability of interacting 2D Weyl fermions",
abstract = "The Coulomb interaction in systems of quasi-relativistic massless electrons has an unscreened long-range component at variance with conventional correlated metals.We used nuclear magnetic resonance (NMR) measurements to reveal unusual spin correlations of two-dimensional Weyl fermions in an organic material, causing a divergent increase of the Korringa ratio by a factor of 1000 upon cooling, in marked contrast to conventional metallic behavior. Combined with model calculations, we show that this divergence stems from an interaction-driven velocity renormalization that almost exclusively suppresses zero-momentum spin fluctuations. At low temperatures, the NMR relaxation rate shows an unexpected increase; numerical analyses show that this increase corresponds to internode excitonic fluctuations, a precursor to a transition from massless to massive quasiparticles.",
author = "Michihiro Hirata and Kyohei Ishikawa and Genki Matsuno and Akito Kobayashi and Kazuya Miyagawa and Masafumi Tamura and Claude Berthier and Kazushi Kanoda",
note = "Funding Information: We thank K. Nomura for critical discussions and reading of the manuscript; D. Basko for technical help with RG calculations; M. O. Goerbig for support and discussions; J. S. Kinyon for fruitful discussions; and H. Fukuyama, N. Nagaosa, H. Isobe, H. Kohno, Y. Suzumura, M. Ogata, T. Osada, C. Hotta, H. Yasuoka, D. Liu, H. Nojiri, T. Kihara, H. Mukuda, M. Tokunaga, Y. Maeno, W. Li, M. Potemski, M.-H. Julien, H. Mayaffre, and M. Horvati{\'c} for helpful discussions and comments. Supported by MEXT/JSPS KAKENHI grants 20110002, 21110519, 24654101, 25220709, 15K05166, 15H02108, 17K05532 and 17K14330; JSPS Postdoctoral Fellowship for Research Abroad grant 66, 2013; the MEXT Global Center of Excellence Program at the University of Tokyo (Physical Sciences Frontier grant G04); the Kurata Memorial Hitachi Science and Technology Foundation (G.M. and A.K.); and the Motizuki Fund of the Yukawa Memorial Foundation (M.H.). The data presented in this paper are available upon request to the first author.",
year = "2017",
month = dec,
day = "15",
doi = "10.1126/science.aan5351",
language = "English",
volume = "358",
pages = "1403--1406",
journal = "Science",
issn = "0036-8075",
publisher = "American Association for the Advancement of Science",
number = "6369",
}