发表机构
Università della Calabria; INFN（卡拉布里亚大学; 意大利国家核物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过含时密度泛函理论计算，揭示扭转双层石墨烯在大角度色散带和小角度准平带中分别呈现狄拉克等离激元与带间等离激元，后者能量经标定位于中红外范围。
AI 中文摘要
利用含时密度泛函理论在随机相位近似下，探索了扭转双层石墨烯在大角度色散带和小角度准平带区域的动态介电响应。在参考双层石墨烯层间距下，最大角度结构中的弱耦合保持了狄拉克色散和本征π等离激元。电子掺杂激活了二维狄拉克等离激元，其能量遵循近似的几何扭转角标度，而声学类分支仍嵌入单粒子连续谱中。第一魔角超胞因过大而难以处理，故用一个可处理的晶胞表示，其层间距减小到与角度相关的魔距，此时费米能级附近出现四个准平带。这些带的局部占据产生了一种色散的低能等离激元样激发，但在共振处没有明显的介电零点。相反，识别出一种不同的带间等离激元，由涉及准平流形和邻近高态密度区域的跃迁所支持。能带能量重标定将其特征能量置于魔角附近测得的带间集体激发中红外范围内。
英文摘要
The dynamical dielectric response of twisted bilayer graphene is explored in large-angle dispersive-band and small-angle quasi-flat-band regimes using time-dependent density-functional theory within the random-phase approximation. At the reference bilayer-graphene interlayer distance, weak coupling in the largest-angle structures preserves Dirac dispersions and the intrinsic $π$ plasmon. Electron doping activates a two-dimensional Dirac plasmon with energies obeying approximate geometric twist-angle scaling, while acoustic-like branches remain embedded in the single-particle continuum. The prohibitively large first-magic-angle supercell is represented by a tractable cell with its interlayer separation reduced to the angle-dependent magic distance, where four quasi-flat bands emerge around the Fermi level. Their partial occupation produces a dispersive low-energy plasmon-like excitation without a clear dielectric zero at resonance. A distinct interband plasmon is instead identified, supported by transitions involving the quasi-flat manifold and neighboring high-density-of-states regions. Band-energy rescaling places its characteristic energy in the mid-infrared range of interband collective excitations measured near the magic angle.
