Anomalous spin correlations and excitonic instability of interacting 2D Weyl fermions

Michihiro Hirata, Kyohei Ishikawa, Genki Matsuno, Akito Kobayashi, Kazuya Miyagawa, Masafumi Tamura, Claude Berthier, Kazushi Kanoda

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)1403-1406
Number of pages4
Issue number6369
Publication statusPublished - 2017 Dec 15

ASJC Scopus subject areas

  • General


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