  The stimulating connection between the reversal of near field plasmonic
binding force and the role of symmetry breaking has not been investigated in
detail in literature. As both bonding and anti-bonding modes are present in the
visible spectra of well-known spherical plasmonic heterodimer sets, binding
force reversal is commonly believed to occur for all such heterodimers. But our
work suggests a very different proposal. We demonstrate that for the symmetry
broken heterodimer configurations: reversal of lateral (for on-axis
heterodimers) and longitudinal (for off-axis heterodimers: end-fire and nearly
end-fire configurations) near field binding force follow fully distinct
mechanisms; i.e. later one on relative orientation and constructive
dipole-quadrupole resonance but the former one on light polarization and the
induced electric resonance. Interestingly, the reversal of longitudinal near
field binding force can be easily controlled just by changing the direction of
light propagation or just their relative orientation. Though it is commonly
believed that plasmonic forces mostly arise from the surface force and Fano
resonance can be a promising way to achieve binding force reversal; our study
based on Lorentz force dynamics suggests notably opposite proposals (for both
instances) for the case of plasmonic spherical heterodimers. Observations of
this article can be very useful for improved sensors, particle clustering and
aggregation.
