Seminar: Matthias Löbl

Semiconductor quantum dots are excellent emitters of single photons and have potential applications in photonic quantum computing and quantum communication. For such applications, the quantum dots ideally emit single photons at one frequency. However, solid-state emitters typically show weak red-shifted emission into the phonon sideband. Here, we present another mechanism that leads to red-shifted photon emission, the so-called radiative Auger process [1]. We observe this process on negatively charged excitons in single quantum dots [2]. Upon the optical recombination of the negative exciton, radiative Auger promotes the second electron of the exciton to a higher shell and red-shifts the emitted photon. We show that the red-shifted emission directly measures the shell structure of the quantum emitter. Furthermore, we measure the photon statistics of the radiative Auger photons. Such measurements give access to the single-electron dynamics, for instance, the p-s relaxation time of an electron in the quantum dot. Finally, we show that the radiative Auger transition can be optically driven and that radiative Auger and fundamental transition form a Lambda-system [3].

[1] T. Aberg et al. Phys. Rev. Lett. 22, 1346 (1969); F. Bloch, Phys. Rev. 48, 187 (1935)
[2] M. C. Löbl et al. Nat. Nanotechnol. 15, 558–562 (2020)
[3] C. Spinnler et al. Nat. Commun. 12, 6575 (2021)