Radiative Auger process in the single-photon limit

Abstract

An excited electron can relax by emitting a photon. In a radiative Auger process, this optical decay leads to the simultaneous excitation of another particle (shake-up). On a single quantum emitter, radiative Auger has not been observed. Here, we report radiative Auger for trions in individual quantum dots. For the trion, just one electron is left after the optical recombination. The radiative Auger process promotes this Auger electron to a higher shell of the quantum dot, and the emitted photon is red-shifted. We show that the energy splitting between this red-shifted photon and the resonance fluorescence directly measures the single-particle splittings of the quantum dot [1], which is otherwise difficult to acquire. We prove the radiative Auger mechanism by measuring the photon statistics and the magnetic field dispersion of the emission. Going beyond the original work in the X-ray spectrum of atoms, we apply quantum optics techniques to the radiative Auger photons. We show how quantum optics gives access to the single-electron dynamics, notably the relaxation and tunneling rates. All these properties of radiative Auger can be exploited on other semiconductor nanostructures and quantum emitters in the solid-state. [1] M. C. Löbl et al., Nat. Nanotechnol. 15, 558–562 (2020)