Intersubband polaritonics revisited

We revisited the intersubband polaritonics - the branch of mesoscopic physics having a huge potential for optoelectronic applications in the infrared and terahertz domains - and found that, contrary to the general opinion, the Coulomb interactions play crucial role in the processes of light-matter coupling in the considered systems. Electron-electron and electron-hole interactions radically change the nature of the elementary excitations in these systems. We show that intersubband polaritons represent the result of the coupling of a photonic mode with collective excitations, and not non-interacting electron-hole pairs as it was supposed in the previous works on the subject.