Quantum Oscillations in Microwave Conductance of Graphene

We report measurements of the microwave-frequency, low-temperature conductance of mechanically-exfoliated graphene on SiO$_2$/Si. The two-terminal microwave conductance ($G$) of a graphene flake is calculated from signals transmitted through a planar metal film pattern which resides on the SiO$_2$ surface and connects to the graphene. At high magnetic field, we observe quantum oscillations of $G$ vs the magnetic field and the graphene carrier density. We find $G$ to be independent of the frequency ($f$) from DC up to 8.5 GHz. This result is consistent with the low $f$ limit, $2\pi f\tau<<1$, where $\tau$ is the scattering time.