  We propose a scheme to measure the mass of a single particle using the
nonlinear response of a 2D nanoresonator with degenerate eigenmodes. Using
numerical and analytical calculations, we show that by driving a square
graphene nanoresonator into the nonlinear regime, simultaneous determination of
the mass and position of an added particle is possible. Moreover, this scheme
only requires measurements in a narrow frequency band near the fundamental
resonance.
