Strong light-matter interaction in graphene induces Floquet-Bloch states, which may also have non-trivial topology [1–4]. Floquet engineering of graphene has been predominantly demonstrated using femtosecond laser pulses, which generate transient, ultra-fast dynamics and short-lived Floquet bands. Here we report transport measurements of epitaxial graphene on SiC irradiated by a continuous-wave mid-infrared laser, using graphene Hall bars fabricated with a top gate that had high transmission in the mid-infrared range [5]. We observed signatures of a long-lived Floquet phase, where a non-equilibrium electronic population is stabilized by the interplay of coherent photoexcitation and incoherent cooling via phonon scattering at the graphene SiC interface and in graphene via graphene acoustic phonons [6]. Our results pave the way to investigations of steady Floquet physics in other types of graphene devices and substrates. One of other types of samples is the twisted bilayer graphene, where the capability to control band structure by varying the twist angle in moiré lattice opens up a new way to explore light-matter interactions [7,8]. The occurrence of flat bands in magic-angle twisted bilayer graphene (MATBLG) enables creation of devices with transport features which can be revealed from their contributions to the photoresponse [9-12]. Recently, we measured the dependence of the mid-infrared photoresponse in MATBLG on gate voltage, while varying light intensity, polarization, and magnetic field, to unveil the complexity of the interplay between light and magnetic field in these systems. 

We acknowledge support from NSF (projects DMR CMP #2104755, DMR CMP #2104770, and OSI #2329006), The National High Magnetic Field Laboratory (NHMFL) is supported by the National Science Foundation through NSF/DMR-1644779, NSF/DMR-2128556 and the State of Florida.