发表机构
Abrikosov Center for Theoretical Physics, MIPT; Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences（阿布里科索夫理论物理中心，莫斯科物理技术学院; 俄罗斯科学院理论与应用电动力学研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文构建无参数变分平均场理论，研究偏置掺杂Bernal双层石墨烯的多体电子相，重现实验关键特征，提出低偏置掺杂区存在更多奇异分数金属相需进一步实验探索。
AI 中文摘要
本文对掺杂且受电偏置的Bernal堆叠（AB）双层石墨烯中的多体电子相开展理论研究。我们构建了无拟合参数的变分平均场理论，对于电子-电子相互作用，采用无参数的随机相位近似来建模短程屏蔽库仑排斥；剩余长程库仑势能由样品几何决定，表现为平行板电容器。我们直接基于实验可控的位移场$\frak D$构建该理论，而非基于相互作用重整化的层间电势差，这使得理论更适合与实验直接对比。所得相图十分丰富，包含多个通过一级和二级相变连接的分数金属态；在较高偏置和掺杂下，出现三种不同的分数金属态，我们按掺杂区域数量和序参量对称性对这些相进行分类。我们的无参数拟合结果重现了近期实验的关键定性与定量特征，包括与分数金属序丧失相关的能量尺度；在较低偏置和掺杂下，该模型稳定了具有更奇特对称性破缺模式的宽范围分数金属相，这表明有必要对后者区域开展进一步实验探索。
英文摘要
The paper presents a theoretical study of many-body electronic phases in doped and electrically biased Bernal-stacked (AB) bilayer graphene. We develop a variational mean-field theory with no fitted parameters. For the electron-electron interaction, we employ a parameter-free random-phase approximation to model the short-range screened Coulomb repulsion. The remaining long-range Coulomb potential energy is dictated by the geometry of the sample, behaving as a parallel-plate capacitor. We formulate the theory directly in terms of the experimentally controlled displacement field $\frak D$ rather than the interaction-renormalized interlayer potential difference. It makes our theory better suited for direct comparison with experiment. The resulting phase diagram is quite rich. It hosts several fractional-metal states connected by first- and second-order transitions. At higher bias and doping, three distinct fractional metallic states emerge. We classify these phases by the number of doped sectors and the symmetry of the order parameters. Our results - obtained without any parameter fitting - reproduce key qualitative and quantitative features of recent experiments. This includes the energy scale associated with the loss of fractional metallic order. At lower bias and doping, the model stabilizes a broad spectrum of fractional-metal phases with more exotic symmetry-breaking patterns. This suggests that further experimental exploration of the latter regime is warranted.
Comments13 pages, 3 figures
