Dynamical Coulomb blockade theory of plasmon-mediated light emission from a tunnel junction

TL;DR

This paper extends a model of plasmon-mediated light emission from tunnel junctions to finite temperatures, showing thermal effects can obscure overbias photon emission, which requires very low temperatures to observe.

Contribution

The authors develop a finite-temperature extension of their dynamical Coulomb blockade model for overbias photon emission in tunnel junctions.

Findings

Thermal smearing masks overbias emission at higher temperatures.

Low temperatures ($k_BT \\ll eV, \\hbar\omega_0$) are necessary to detect correlated tunneling.

The model aligns with experimental conditions for observing overbias emission.

Abstract

Inelastic tunneling of electrons can generate the emission of photons with energies intuitively limited by the applied bias voltage. However, experiments indicate that more complex processes involving the interaction of electrons with plasmon polaritons lead to photon emission with overbias energies. We recently proposed a model of this observation in Phys. Rev. Lett. \textbf{113}, 066801 (2014), in analogy to the dynamical Coulomb blockade, originally developed for treating the electromagnetic environment in mesoscopic circuits. This model describes the correlated tunneling of two electrons interacting with a local plasmon-polariton mode, represented by a resonant circuit, and shows that the overbias emission is due to the non-Gaussian fluctuations. Here we extend our model to study the overbias emission at finite temperature. We find that the thermal smearing strongly masks the overbias emission. Hence, the detection of the correlated tunneling processes requires temperatures $k_BT$ much lower than the bias energy $eV$ and the plasmon energy $\hbar\omega_0$, a condition which is fortunately realized experimentally.