non-classical noise and light emission of an ac-driven tunnel junction

The non-symmetrized noise is crucial for the analysis of light emission in nanojunctions. The latter represent non-classical photon emitters whose description requires a full quantum approach [1]. It was found experimentally that light emission can occur with a photon energy exceeding the applied dc voltage [2], which intuitively should be forbidden due to Pauli principle. This overbias light emission cannot be described by the single-electron physics, but can be explained by 2-electron or even 3-electron process, correlated by a local antenna mode in analogy to the well-known dynamical Coulomb blockade (DCB) [3]. Here, we obtain the non-symmetrized noise for junctions driven by an arbitrarily shaped periodic voltage. We find that when the junction is driven, overbias light emission occurs and exhibits intriguing different features compared to the dc case. For example, multiple peaks appear at integers of the ac driving frequency. Our work generalizes the DCB theory to light emission in driven tunnel junctions and opens the avenue to engineered quantum light sources, which can be tuned purely by applied voltages.

References:
1. M. H. Devoret et al. PRL 1990
2. G. Schull et al. PRL 2009
3. F. Xu et al. PRL 2014, PRB 2016; P.-J. Peters et al. PRL 2018