Photon-emission statistics induced by electron tunneling in plasmonic nanojunctions

We investigate the statistics of photons emitted by tunneling electrons in a single electronic level plasmonic nanojunction. We compute the waiting-time distribution of successive emitted photons w(tau). When the cavity damping rate kappa is larger than the electronic tunneling rate Gamma, we show that in the photon-antibunching regime, w(tau) indicates that the average delay time between two successive photon-emission events is given by 1/Gamma. This is in contrast with the usually considered second-order correlation function of emitted photons, g((2))(tau), which displays the single timescale 1/kappa. Our analysis shows a relevant example for which w(tau) gives independent information on the photon-emission statistics with respect to g((2))(tau), leading to physical insight into the problem. We discuss how this information can be extracted from experiments even in the presence of a nonperfect photon-detection yield.