AI 中文总结
研究菱形四层石墨烯中的维格纳结晶，用投影哈特里 - 福克及含时哈特里 - 福克计算，发现向列型维格纳晶体，确定其相图区域、能带结构等特性及稳定性，还给出了实验识别稳定相的方法。
AI 中文摘要
近期实验报道了菱形石墨烯中存在维格纳晶体（WCs）的证据。在此，我们使用投影哈特里 - 福克（HF）计算和含时哈特里 - 福克（TDHF）计算来研究菱形四层石墨烯中的维格纳结晶。首先进行HF计算，发现向列型WCs（nWCs）自发打破三重旋转对称性\(C_3\)以及\(C_3\)不变的WCs。相图中有两个nWC区域。nWCs和\(C_3\)不变的WCs都是谷极化态且陈数为零，HF能带结构中有正的间接带隙。接着进行TDHF计算测试WC态的局部稳定性，发现所有\(C_3\)不变的WCs和一半的nWCs是局部稳定的，其余nWCs对每单元有两个电子的WC态或金属态不稳定。预测的稳定nWC相可通过扫描隧道显微镜观察其各向异性电荷分布或通过角度分辨输运测量依赖方向的脱钉电压来实验识别。
英文摘要
Recent experiments have reported evidence for Wigner crystals (WCs) in rhombohedral graphene. Here, we investigate Wigner crystallization in rhombohedral tetralayer graphene using projected Hartree-Fock (HF) calculations and time-dependent Hartree-Fock (TDHF) calculations. We first perform HF calculations with one electron per Wigner unit cell, and find nematic WCs (nWCs) that spontaneously break the threefold rotational symmetry $C_3$ and $C_3$-invariant WCs. In particular, there are two nWC regions in the phase diagram: one larger region at large displacement fields and low electron densities, and another smaller region at intermediate fields and high densities. Both the nWCs and the $C_3$-invariant WCs are valley-polarized states with zero Chern number, and have positive indirect gaps in the HF band structure. We then perform TDHF calculations to further test the local stability of the WC states. We find that all $C_3$-invariant WCs and half of the nWCs are locally stable, while the remaining nWCs are unstable towards WCs with two electrons per unit cell or metallic states. The predicted stable nWC phase can be identified experimentally by scanning tunneling microscopy through its anisotropic charge distribution or by angle-resolved transport measurements via a direction-dependent depinning voltage.
Comments8+14 pages, 4+6 figures
