2013/02/16 by G. L. Yu, R. Jalil, Branson Belle +12 · 1 citation
Physics and Astronomy · #cond-mat.mes-hall
paper · pdf · doi:10.1073/pnas.1300599110
published as Proc. Natl Acad. Sci. USA 110, 3282-3286 (2013)
arxiv created 2013/02/16 · arxiv updated 2013/03/06
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.