标题： SU(4)对称模型中AB双层石墨烯的有序态 显示英文标题

标题： Ordered states in AB bilayer graphene in SU(4)-symmetric model

摘要： 我们应用SU(4)对称模型来研究AB堆叠双层石墨烯(AB-BLG)中的可能有序态。系统的哈密顿量在某些假设下具有这种对称性。在这种模型中，多分量序参量可以表示为一个$4\times4$矩阵$\hat{Q}$。利用平均场近似法，我们推导出一个关于$\hat{Q}$的自洽方程。在所得到的方程的可能解中，包括异常量子霍尔态、自旋、电荷、自旋谷密度波、层间激子相及其组合。我们认为，所提出的这种方法是分类AB-BLG中有序态的一个有用的工具。SU(4)对称模型的有序态表现出广泛的简并性。通过考虑被忽略的非SU(4)对称项、无序、衬底以及其他扰动，这些简并性可以被消除。有序态对这些因素有不同的敏感度。这表明，对于AB-BLG而言，基态的有序类型是一种非普适性质，易受到外在条件具体细节的影响。 显示英文摘要

摘要： We apply SU(4)-symmetric model to examine possible ordered states in AB stacked bilayer graphene (AB-BLG). The Hamiltonian of the system possesses this symmetry under certain assumptions. In such a model the multicomponent order parameter can be presented as a $4\times4$ matrix $\hat{Q}$. Using a mean field approximation, we derive a self-consistency equation for $\hat{Q}$. Among possible solutions of the obtained equation there are anomalous quantum Hall states, spin, charge, spin-valley density waves, inter-layer excitonic phases and their combinations. We argue that the proposed approach is a useful tool for classification of the ordered states in AB-BLG. The ordered states of the SU(4)-symmetric model demonstrate extensive degeneracies. The degeneracies can be removed by taking into account the neglected non-SU(4)-symmetric terms, disorder, substrate, as well as other perturbations. The ordered states have varying sensitivity to these factors. This suggests that, for AB-BLG, a ground state ordering type is a non-universal property, susceptible to particulars of extrinsic conditions.