论文标题
在范霍夫场景中的扭曲和非扭曲石墨烯层中的级联过渡
Cascade of transitions in twisted and non-twisted graphene layers within the van Hove scenario
论文作者
论文摘要
由扭曲的双层石墨烯中的可压缩性和STM光谱的测量动机，我们分析了van霍夫奇异性附近巡回费米子的对称性破裂模式。利用Landau功能的近似SU（4）对称性，我们表明旋转/同源阶参数的结构随着级联过渡的填充而增加。我们从不同的旋转/同源订单中计算出对费米子的反馈，并认为每个顺序以特定方式将最初的4倍退化的范霍夫峰分开，这与STM数据和可压缩性测量相一致，从而在扭曲的毛线层中提供了对过渡层的统一解释。我们的结果取决于对SU（4） - 对称Landau功能的通用分析，并且在特定的基础费米模型之外是有效的。我们认为，类似的范霍夫场景解释了非扭曲的Bernal双层和菱形三层石墨烯中的一系列相变。
Motivated by measurements of compressibility and STM spectra in twisted bilayer graphene, we analyze the pattern of symmetry breaking for itinerant fermions near a van Hove singularity. Making use of an approximate SU(4) symmetry of the Landau functional, we show that the structure of the spin/isospin order parameter changes with increasing filling via a cascade of transitions. We compute the feedback from different spin/isospin orders on fermions and argue that each order splits the initially 4-fold degenerate van Hove peak in a particular fashion, consistent with the STM data and compressibility measurements, providing a unified interpretation of the cascade of transitions in twisted bilayer graphene. Our results follow from a generic analysis of an SU(4)-symmetric Landau functional and are valid beyond a specific underlying fermionic model. We argue that an analogous van Hove scenario explains the cascade of phase transitions in non-twisted Bernal bilayer and rhombohedral trilayer graphene.
