Dipole-dipole shift of quantum emitters coupled to surface plasmons of a nanowire

Placing quantum emitters close to a metallic nanowire, an effective interaction can be achieved over distances large compared to the resonance wavelength due to the strong coupling between emitters and the surface plasmon modes of the wire. This leads to modified collective decay rates, as well as to Lamb and dipole-dipole shifts. In this paper, we present a general method for calculating these level shifts, which we subsequently apply to the case of a pair of atoms coupled to the guided modes of a nanowire.