The spontaneous emission properties of a two-level emitter embedded in a negative permeability slab near the interface between a negative permeability slab and a negative permittivity slab are investigated. When the impedances of the two slabs are matched and the dissipation of the material is small, the structure forms a very good single-mode cavity for surface plasmons. The extremely high local density of states of surface plasmons results in ultrastrong coupling between the atom and the surface plasmons, and then large vacuum Rabi frequency. A damped vacuum Rabi oscillation occurs in the dynamic evolution of the excited atom close to the interface. The atomic emission spectrum displays an asymmetric two-peak structure with the peak separation equal to the vacuum Rabi frequency.

• Received 26 February 2012

DOI:https://doi.org/10.1103/PhysRevA.86.033819