Interaction phenomena in graphene seen through quantum capacitance

TL;DR

This study uses quantum capacitance measurements on high-quality graphene to explore many-body effects, revealing spectrum renormalization, Landau level splitting, and reentrant compressibility behavior under magnetic fields.

Contribution

It provides new insights into electron-electron interactions and many-body phenomena in graphene through detailed capacitance measurements in various magnetic fields.

Findings

Renormalization of the linear spectrum due to interactions

Splitting of Landau levels into quartets with energy gaps

Reentrant compressibility behavior in high magnetic fields

Abstract

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.