Superradiance and subradiance in plasmonic nanochannels

We demonstrate a plasmonic route to superradiance and subradiance effects over distances comparable to the operating wavelength. Superradiant and subradiant modes are excited by a collection of two-level quantum emitters inside plasmonic nanochannels. These channels can provide an effective epsilon-near-zero operation in their cut-off frequency and Fabry-P\'erot resonances at higher frequencies. The related plasmonic resonant modes are found to efficiently enhance the constructive (superradiance) or destructive (subradiance) interference between different quantum emitters located inside the nanochannels. By increasing the number of emitters located in the elongated plasmonic channel, the superradiance effect is enhanced at the epsilon-near-zero operation, leading to a strong increase in the collective spontaneous emission rate. In addition, the separation distance between neighboring emitters and their emission wavelengths can be changed to dynamically control the collective emission properties of the plasmonic system. It is envisioned that the dynamic modification between quantum superradiant and subradiant modes will find applications in quantum communication and computing systems.