  We investigate lateral recoil forces exerted on nanoparticles located near
plasmonic platforms with in-plane nonreciprocal response. To this purpose, we
first develop a comprehensive theoretical framework based on the Lorentz force
within the Rayleigh approximation combined with nonreciprocal Green's functions
and then derive approximate analytical expressions to model lateral recoil
forces, demonstrating their explicit dependence on the dispersion relation of
the system and unveiling the mechanisms that govern them. In particular, a
dominant lateral recoil force component appears due to the momentum imbalance
of nonreciprocal surface plasmons supported by the platform. This force can be
orders of magnitude larger than other recoil force components, acts only along
or against the direction of the external bias, and is quasi-independent of the
direction, polarization, and wavelength of the incident plane wave. Lateral
recoil forces are explored using drift-biased graphene metasurfaces, a platform
that is also proposed to sort nanoparticles as a function of their size.
Nonreciprocal plasmonic systems may enable new venues to trap, bind, and
manipulate nanoparticles and to alleviate some of the challenges of
conventional optical tweezers.
