  We theoretically investigate the properties of crossing for two perpendicular
subwavelength plasmonic slot waveguides. We show that, when encountering nano
intersection, the crosstalk for the direct crossing is around 25%, almost same
as throughout. In terms of symmetry considerations and resonant-tunnelling
effect, we design compact cavity-based structures. Our results show that the
crosstalk is eliminated and the throughput reaches the unity on resonance.
Simulations results are in agreement with those from the coupled-model theory.
When taking into account of the material loss, due to the unchanged symmetry
properties of the modes, the crosstalk is still suppressed. Our results may
open a way to construct nanoscale crossings for high-density nanoplasmonic
integration circuits.
