  Transport properties of graphene - superconductor junction has been studied
extensively to understand the interplay of the relativistic Dirac
quasiparticles and superconductivity. Though shot noise measurements in
graphene has been performed to realize many theoretical predictions, both at
zero magnetic field as well as quantum Hall (QH) regime, its junction with
superconductor remain unexplored. Here, we have carried out the shot noise
measurements in an edge contacted bilayer graphene - Niobium superconductor
junction at zero magnetic field as well as QH regime. At the Dirac point we
have observed a Fano factor ~ 1/3 above the superconducting gap and a
transition to an enhanced Fano factor ~ 0.5 below the superconducting gap. By
changing the carrier density we have found a continuous reduction of Fano
factor for both types of carriers, however the enhancement of Fano factor
within the superconducting gap by a factor of ~ 1.5 is always preserved. The
enhancement of shot noise is also observed in the QH regime, where the current
is carried by the edge state, below the critical magnetic field and within the
superconducting gap. These observations clearly demonstrate the enhanced charge
transport at the graphene-superconductor interface.
