论文标题
中性魔术角双层石墨烯：condon不稳定性和手性共振
Neutral magic-angle bilayer graphene: Condon instability and chiral resonances
论文作者
论文摘要
我们讨论了扭曲的双层石墨烯在中立点接近连续体模型（CM）中的完整光学响应。首先，我们确定与基础$ d_3 $对称性一致的三个不同的通道，从而产生总，磁性和手性响应。其次，我们在魔术角$θ_m$附近计算了数值计算的完整光学响应，该响应将CM直接映射到有效的两波段模型上。此外，我们表明，$θ_m$附近CM的地面不稳定是不稳定的，这是一种所谓的Condon不稳定。第三，由于较大的逆流，具有典型波数的声激发比光学的激发具有更大的能量，并且在某些频率下，它们的能量密度可能会大大增强，在某些频率下，我们将其表示为{\ IT手性共振}。最后，我们讨论了光学响应的对称关系及其对手性反应的后果。
We discuss the full optical response of twisted bilayer graphene at the neutrality point close to the magic angle within the continuum model (CM). Firstly, we identify three different channels consistent with the underlying $D_3$ symmetry, yielding the total, magnetic, and chiral response. Secondly, we numerically calculate the full optical response in the immediate vicinity of the magic angle $θ_m$ which provides a direct mapping of the CM onto an effective two-band model. We, further, show that the ground-state of the CM in the immediate vicinity of $θ_m$ is unstable towards transverse current fluctuations, a so-called Condon instability. Thirdly, due to the large counterflow, the acoustic plasmonic excitations with typical wave numbers have larger energies than the optical ones and their energy density may be largely enhanced at certain frequencies which we denominate as {\it chiral resonances}. Finally, we discuss symmetry relations for the optical response and their consequences for the chiral response.
