Superradiant phase transitions and spontaneous superradiant photon current in a double-cavity system

Abstract As a crucial role in various aspects of quantum transport, quantum pumping usually refers to the controlled movement of particles through external manipulation. This work reports a unique occurrence of self-organized quantum pumping for photons without any external driving in a spin–cavity system, where an assemble of quantum emitters interact with photonic modes confined in two tunneling-coupled cavities. Specifically, undermirror-symmetry breaking of cavity dissipations and spin–cavity coupling strengths, a steady photon current spontaneously emerges between the two cavities when the system reaches its superradiant phase. Investigation shows that cavity dissipation, which acts as a pump, assists the system to sustainably extract photons from the surroundings and generate a superradiant photon current with photon loss via dissipation channels. Generating with Z 2 spontaneous symmetry breaking, this kind of counter-intuitive photon current provides a spontaneous regime for the occurrence of current in real space.