近日，美国哈佛大学Amir Yacoby团队研究了扭曲三层石墨烯中轻电子和重电子之间的可调谐相互作用。相关论文于2025年6月26日发表在《自然—物理学》杂志上。
在具有多个能带的系统中，具有不同有效质量的电子之间的相互作用驱动了在单能带系统中不会发生的相关现象。魔角扭曲三层石墨烯是探索这种效应的可调平台，在其平带中容纳重电子，在色散带中容纳离域的轻狄拉克电子。该系统中的超导性比没有色散带的莫尔材料跨越了更宽的相空间范围，这表明带间相互作用会影响相关相的稳定。
研究组通过扫描单电子晶体管显微镜进行局部压缩性测量，研究了魔角扭曲三层石墨烯中轻电子和重电子之间的相互作用。他们确定，尽管平带扇区存在间隙，但在几个整数莫尔带填充物附近的弱不可压缩特征在费米能级上承载了有限数量的轻狄拉克电子。在接近电荷中性的较高磁场下，他们发现一个相变序列在近10 μm，但表现出复杂的空间依赖性。计算表明，狄拉克扇形可以被视为类似于自旋和谷自由度的类似物。
附：英文原文
Title: Tunable interplay between light and heavy electrons in twisted trilayer graphene
Author: Pierce, Andrew T., Xie, Yonglong, Park, Jeong Min, Cai, Zhuozhen, Watanabe, Kenji, Taniguchi, Takashi, Jarillo-Herrero, Pablo, Yacoby, Amir
Issue&Volume: 2025-06-26
Abstract: In systems with multiple energy bands, the interplay between electrons with different effective masses drives correlated phenomena that do not occur in single-band systems. Magic-angle twisted trilayer graphene is a tunable platform for exploring such effects, hosting both heavy electrons in its flat bands and delocalized light Dirac electrons in dispersive bands. Superconductivity in this system spans a wider range of phase space than moiré materials without dispersive bands, suggesting that interband interactions influence the stabilization of correlated phases. Here we investigate the interplay between the light and heavy electrons in magic-angle twisted trilayer graphene by performing local compressibility measurements with a scanning single-electron-transistor microscope. We establish that weak incompressibility features near several integer moiré band fillings host a finite population of light Dirac electrons at the Fermi level, despite a gap opening in the flat band sector. At higher magnetic field near charge neutrality, we find a phase transition sequence that is robust over nearly 10μm but exhibits complex spatial dependence. Calculations establish that the Dirac sector can be viewed as flavour analogous to the spin and valley degrees of freedom.
DOI: 10.1038/s41567-025-02956-z
Source: https://www.nature.com/articles/s41567-025-02956-z