Phonon-enhanced graphene photoresponse for mid-infrared light

The mid-infrared spectral region is crucial for fundamental research and spectroscopy as well as for technology, for example for applications in thermal imaging for defense or medical purposes. Graphene enables new routes in the field of mid-infrared detection due to its broadband absorption, tunable optical properties and flexibility [1, 2]. Moreover, several relevant energy scales for graphene lie the in the mid-infrared range, such as the Fermi energy tunable by a standard back-gate, the energy of graphene and substrate optical phonons and the energy of graphene plasmons. This recently led to the observation of interesting phenomena such as tunable plasmon excitations [3] and plasmon-phonon hybridization [4,5]. However, the role of bulk and surface phonons of the substrate on the photoresponse of unbiased graphene is not fully understood.