  Plasmonic, as a rapidly growing research field, provides new pathways to
guide and modulate highly confined light in the microwave to the optical range
of frequencies. We demonstrate a plasmonic slot waveguide, at the nanometer
scale, based on high transition temperature superconductor BSCCO, to
facilitates the manifestation of the chip-scale millimeter waves to terahertz
integrated circuitry operating at cryogenic temperatures. We investigate the
effect of geometrical parameters on the modal characteristics of the BSCCO
plasmonic slot waveguide between 100 GHz and 500 GHz. In addition, we
investigate the thermal sensing of the modal characteristics of the nanoscale
superconducting slot waveguide and show that at a lower frequency, the
fundamental mode of the waveguide has a larger propagation length, a lower
effective refractive index, and a strongly localized modal energy. Moreover, we
find that our device offers a larger SPP propagation length and higher field
confinement than the gold plasmonic waveguides at broad temperature ranges
below BSCCO Tc. The proposed device can open up a new route towards realizing
cryogenic low-loss photonic integrated circuitry at the nanoscale.
