Weak antilocalization of composite fermions in graphene

Abstract

We demonstrate experimentally that composite fermions in monolayer graphene display weak antilocalization. Our experiments deal with fractional quantum Hall (FQH) states in high-mobility, suspended graphene Corbino disks in the vicinity of $\ensuremath{\nu}=1/2$. We find a strong temperature dependence of conductivity $\ensuremath{\sigma}$ away from half filling, which is consistent with the expected electron-electron interaction-induced gaps in the FQH state. At half filling, however, the temperature dependence of conductivity $\ensuremath{\sigma}(T)$ becomes quite weak, as anticipated for a Fermi sea of composite fermions, and we find a logarithmic dependence of $\ensuremath{\sigma}$ on $T$. The sign of this quantum correction coincides with the weak antilocalization of graphene composite fermions, indigenous to chiral Dirac particles.