Nonlinear vs. bolometric radiation response and phonon thermal conductance in graphene-superconductor junctions

Abstract: Graphene is a promising candidate for building fast and ultra-sensitive bolometric detectors due to its weak electron-phonon coupling and low heat capacity. In order to realize a practical graphene-based bolometer, several important issues, including the nature of radiation response, coupling efficiency to the radiation and the thermal conductance need to be carefully studied. Addressing these issues, we present graphene-superconductor junctions as a viable option to achieve efficient and sensitive bolometers, with the superconductor contacts serving as hot electron barriers. For a graphene-superconductor device with highly transparent interfaces, the resistance readout in the presence of radio frequency radiation is dominated by non-linear response. On the other hand, a graphene-superconductor tunnel device shows dominantly bolometric response to radiation. For graphene devices fabricated on $SiO_{2}$ substrates, we confirm recent theoretical predictions of $T^{2}$ temperature dependence of phonon thermal conductance in the presence of disorder in the graphene channel at low temperatures.