Anomalous spin correlations and excitonic instability of interacting 2D Weyl fermions
Anomalous spin correlations and excitonic instability of interacting 2D Weyl fermions
复制标题
DOI：
10.1126/science.aan5351
复制
发表时间：
2017-02
期刊：
影响因子：
56.9
通讯作者：
M. Hirata;K. Ishikawa;Genki Matsuno;A. Kobayashi;K. Miyagawa;M. Tamura;C. Berthier;K. Kanoda
中科院分区：
文献类型：
--
作者：
M. Hirata;K. Ishikawa;Genki Matsuno;A. Kobayashi;K. Miyagawa;M. Tamura;C. Berthier;K. Kanoda
长期以来，在材料的签名中，在材料的签名中寻找相关性，这些材料具有线性分散的材料，这些能量分散剂，这些效果（例如，这些效果都在研究中，这些效果仍然令人沮丧。 Ent one with enhanced electronic correlations. The unusual temperature dependence of spin-related properties in this material indicated strong correlations among the linearly dispersing electronics. Science, this issue p. 1403 Nuclear magnetic resonance measurements show correlations among linearly dispersing electronics in a layered organic material. The Coulomb interaction in systems of quasi-relativistic massless electronics has an unscreened long-range component at variance with常规的相关金属。我们使用核磁共振（NMR）测量结果揭示了有机材料中二维Weyl fermions的异常自旋相关性，从而在冷却后与传统的金属行为相比，在冷却时，korringa比率增加了1000倍。典型在低温下抑制零孔自旋波动。
Finding correlations in a Dirac-cone material Researchers have long been on the lookout for signatures of electron-electron interactions in materials whose electrons have linear energy dispersions represented by Dirac cones, such as graphene. However, these effects have remained frustratingly small. Hirata et al. used nuclear magnetic resonance to study the layered organic material α-(BEDT-TTF)2I3, in which a phase featuring Dirac cones is known to be adjacent to one with enhanced electronic correlations. The unusual temperature dependence of spin-related properties in this material indicated strong correlations among the linearly dispersing electrons. Science, this issue p. 1403 Nuclear magnetic resonance measurements show correlations among linearly dispersing electrons in a layered organic material. 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.