School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, United Kingdom.
Proc Natl Acad Sci U S A. 2013 Feb 26;110(9):3282-6. doi: 10.1073/pnas.1300599110. Epub 2013 Feb 11.
Capacitance measurements provide a powerful means of probing the density of states. The technique has proved particularly successful in studying 2D electron systems, revealing a number of interesting many-body effects. Here, we use large-area high-quality graphene capacitors to study behavior of the density of states in this material in zero and high magnetic fields. Clear renormalization of the linear spectrum due to electron-electron interactions is observed in zero field. Quantizing fields lead to splitting of the spin- and valley-degenerate Landau levels into quartets separated by interaction-enhanced energy gaps. These many-body states exhibit negative compressibility but the compressibility returns to positive in ultrahigh B. The reentrant behavior is attributed to a competition between field-enhanced interactions and nascent fractional states.
电容测量提供了一种探测态密度的强大手段。该技术在研究二维电子系统方面已被证明特别成功，揭示了许多有趣的多体效应。在这里，我们使用大面积高质量的石墨烯电容器来研究这种材料在零磁场和高磁场下的态密度行为。在零磁场中，由于电子-电子相互作用，线性谱明显的重整化得到了观察。量子化场导致自旋和谷简并的朗道能级分裂成由相互作用增强的能隙分开的四重态。这些多体态表现出负压缩性，但在超高 B 下压缩性恢复为正。这种再进入行为归因于增强的相互作用和新生分数态之间的竞争。
