Photon-assisted shot noise in graphene for THz photo-detection

F.D. Parmentier, L. Serkovic-Loli, P. Roulleau and D.C. Glattli

Service de Physique de l'Etat Condensé, DSM/IRAMIS/SPEC, CNRS UMR 3680, CEA Saclay

When subjected to electromagnetic radiation, the fluctuation of the current across a quantum conductor increases. This additional noise, called photon-assisted shot noise, arises from the generation and subsequent partition of an out-of-equilibrium energy distribution function in the leads of the conductor caused by the impinging radiation. Measuring the photon-assisted shot noise allows to characterize this radiation; in particular, one expects singularities in the shot noise whenever the DC electric potential applied to the conductor is equal to the frequency of the radiation multiplied by Planck’s constant. The physics of photon-assisted shot noise has been thoroughly investigated at microwave frequencies up to 20 GHz, and its robustness suggests that it could be used to realize wide bandwidth, frequency-resolved photodetectors working in the THz regime, and operated at liquid Helium temperatures. Here, we present first measurements of the noise generated in a graphene nanoribbon subjected to a THz radiation. Our results show signatures of photon-assisted shot noise, as well as a non negligible role of heating in the sample. This validates the principle of our THz detector, and offers new insights into energy relaxation in graphene.