Resistively detected microwave absorption in highly twisted bilayer graphene*

Resistively detected microwave absorption measurements of high-mobility two-dimensional (2D) electron systems are a powerful tool to explore the high-frequency spectroscopic and non-equilibrium response of correlated electron states in these systems. We have performed low-temperature magneto-transport experiments on a hexagonal boron nitride and dual graphite encapsulated twisted graphene bilayer while simultaneously irradiating the sample with microwave frequency photons. In this device the twist angle between the graphene flakes is relatively large, leading to a low-energy decoupling of the layers. Dual graphite gates allow us independent control of both the charge carrier density in the bilayer and a displacement electric field perpendicular to the 2D stack. We find that the differential magneto-conductance of the device, defined as the difference in conductance with and without microwave irradiation, shows well-defined oscillations in a large filling factor range down to the lowest Landau level. The dependence of these conductance oscillations on the magnetic field, displacement field, filling factor and microwave frequency will be discussed