The pseudo-relativistic chiral electrons in 2D graphene and 3D topological semimetals, known as the massless Dirac or Weyl fermions, constitute various intriguing issues in modern condensed-matter physics. In particular, the issues linked to the Coulomb interaction between the chiral electrons attract great attentions due to their unusual features, namely, the interaction is not screened and has a long-ranged property near the charge-neutrality point, in clear contrast to its screened and short-ranged properties in the conventional correlated materials. In graphene, this long-range interaction induces an anomalous logarithmic renormalization of the Fermi velocity, which causes a nonlinear reshaping of its Dirac cone. In addition, for strong interactions, it even leads to the predictions of an excitonic condensation with a spontaneous mass generation. The interaction, however, would seem to be not that large in graphene, so that the latter phenomenon appears to have not yet been observed. Contrastingly, the interaction is probably large in the pressurized organic material α-(BEDT-TTF)₂I₃, where a 2D massless-Dirac-fermion phase emerges next to a correlated insulating phase. Therefore, an excellent testing ground would appear in this material for the studies of both the velocity renormalization and the mass generation, as well as for those of the short-range electronic correlations. In this review, we give an overview of the recent progress on the understanding of such interacting chiral electrons in 2D, by placing particular emphasis on the studies in graphene and α-(BEDT-TTF)₂I₃. In the first half, we briefly summarize our current experimental and theoretical knowledge about the interaction effects in graphene, then turn attentions to the understanding in α-(BEDT-TTF)₂I₃, and highlight its relevance to and difference from graphene. The second half of this review focusses on the studies linked to the nuclear magnetic resonance experiments and the associated model calculations in α-(BEDT-TTF)₂I₃. These studies allow us to discuss the anisotropic reshaping of a tilted Dirac cone together with various electronic correlations, and the precursor excitonic dynamics growing prior to a condensation. We see these provide unique opportunities to resolve the momentum dependence of the spin excitations and fluctuations that are strongly influenced by the long-range interaction near the Dirac points.

2D 石墨烯和 3D 拓扑半金属中的伪相对论手征电子，被称为无质量狄拉克或外尔费米子，构成了现代凝聚态物理学中的各种有趣问题。特别是手性电子之间的库仑相互作用问题因其不寻常的特征而备受关注，即相互作用没有被屏蔽，并且在电荷中性点附近具有长程性质，与其屏蔽形成鲜明对比。和传统相关材料的短程特性。在石墨烯中，这种长程相互作用引起费米速度的异常对数重整化，从而导致其狄拉克锥的非线性重塑。此外，对于强相互作用，它甚至导致了对自发质量产生的激子凝聚的预测。然而，这种相互作用在石墨烯中似乎没有那么大，因此后一种现象似乎还没有被观察到。相比之下，在加压有机材料中的相互作用可能很大α -(BEDT-TTF) ₂ I ₃，其中二维无质量狄拉克费米子相出现在相关绝缘相旁边。因此，该材料将出现一个极好的试验场，用于研究速度重整化和质量生成，以及短程电子相关性的研究。在这篇综述中，我们通过特别强调石墨烯和α -(BEDT-TTF) ₂ I ₃的研究，概述了在二维中理解这种相互作用的手性电子的最新进展。在前半部分，我们简要总结了我们目前关于石墨烯相互作用效应的实验和理论知识，然后将注意力转向对石墨烯的理解。α -(BEDT-TTF) ₂ I ₃，并突出其与石墨烯的相关性和不同之处。本综述的后半部分重点关注与核磁共振实验相关的研究以及α -(BEDT-TTF) ₂ I _{3 中}的相关模型计算。这些研究使我们能够讨论倾斜狄拉克锥的各向异性重塑以及各种电子相关性，以及凝聚之前增长的前体激子动力学。我们看到这些提供了独特的机会来解决受狄拉克点附近长程相互作用强烈影响的自旋激发和波动的动量依赖性。