The role of electron-electron interactions in two-dimensional Dirac fermions
The role of electron-electron interactions in two-dimensional Dirac fermions
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DOI：
10.1126/science.aao2934
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发表时间：
2018-03
期刊：
影响因子：
56.9
通讯作者：
Ho-Kin Tang;J. Leaw;J. N. Rodrigues;I. Herbut;P. Sengupta;P. Sengupta;F. Assaad;S. Adam;S. Adam
中科院分区：
文献类型：
--
作者：
Ho-Kin Tang;J. Leaw;J. N. Rodrigues;I. Herbut;P. Sengupta;P. Sengupta;F. Assaad;S. Adam;S. Adam
尽管石墨烯通常被认为是一种电子与电子之间的相互作用可以忽略不计的材料，但它的一些特性无法用如此简单的图像来解释。Tang等人进行了全面的量子蒙特卡罗数值计算，考虑了像石墨烯这样具有二维（2D）狄拉克电子的系统中的远程和接触相互作用。不同的二维狄拉克材料系统，如拓扑绝缘体和各种衬底上的石墨烯，位于所得相图的不同部分。一种非微扰量子蒙特卡罗方法探讨了石墨烯和相关材料中相互作用的后果。电子-电子相互作用在二维狄拉克费米子系统中的作用仍然是个谜。利用结合库仑相互作用的接触和远程部分的非摄动数值和分析技术，我们确定了前面讨论过的两种状态：向强相关莫特绝缘体的格罗斯- neveu跃迁和具有对数发散费米速度的半金属状态，这些状态由随机相位近似精确描述。我们预测狄拉克费米子的实验实现跨越了这个交叉，这决定了费米速度是通过相互作用增加还是减少。我们解释了几个长期存在的谜团，包括为什么石墨烯中观察到的费米速度始终比从头计算得到的值大20%左右，以及为什么不同衬底上的石墨烯表现出不同的行为。
Computers tease out interaction effects Although graphene is often thought of as a material in which electron-electron interactions are negligible, some of its properties cannot be explained by such a simple picture. Tang et al. undertook comprehensive quantum Monte Carlo numerical calculations that consider both long-range and contact interactions in systems that, like graphene, have two-dimensional (2D) Dirac electrons. Different 2D Dirac materials systems, such as topological insulators and graphene on various substrates, reside in different parts of the resulting phase diagram. Science, this issue p. 570 A nonperturbative quantum Monte Carlo method probes the consequences of interactions in graphene and related materials. The role of electron-electron interactions in two-dimensional Dirac fermion systems remains enigmatic. Using a combination of nonperturbative numerical and analytical techniques that incorporate both the contact and long-range parts of the Coulomb interaction, we identify the two previously discussed regimes: a Gross-Neveu transition to a strongly correlated Mott insulator and a semimetallic state with a logarithmically diverging Fermi velocity accurately described by the random phase approximation. We predict that experimental realizations of Dirac fermions span this crossover and that this determines whether the Fermi velocity is increased or decreased by interactions. We explain several long-standing mysteries, including why the observed Fermi velocity in graphene is consistently about 20% larger than values obtained from ab initio calculations and why graphene on different substrates shows different behaviors.