Florian Ungar

Nonlinear cavity feeding and unconventional photon statistics in solid-state cavity QED revealed by many-level real-time path-integral calculations

The generation of photons in a microcavity coupled to a laser-driven quantum dot interacting with longitudinal acoustic (LA) phonons is studied in the regime of simultaneously strong driving and strong dot-cavity coupling. The stationary cavity photon number is found to depend in a non-trivial way on the detuning between the laser and the exciton transition in the dot. In particular, the maximal efficiency of the cavity feeding is obtained for detunings corresponding to transition energies between cavity-dressed states with excitation numbers larger than one. Phonons significantly enhance the cavity feeding at large detunings. In the strong-driving, strong-coupling limit, the photon statistics is highly non-Poissonian. While without phonons a double-peaked structure in the photon distribution is predicted, phonons make the photon statistics thermal-like with very high effective temperatures

Quantum kinetic equations for the ultrafast spin dynamics of excitons in diluted magnetic semiconductor quantum wells after optical excitation

\sim 10^5

Influence of nonmagnetic impurity scattering on spin dynamics in diluted magnetic semiconductors

K, even for low phonon temperatures

Ultrafast spin dynamics in II-VI diluted magnetic semiconductors with spin-orbit interaction

\sim 4

Dependence of quantum kinetic effects in the spin dynamics of diluted magnetic semiconductors on the excitation conditions

K. These results were obtained by numerical calculations where the driving, the dot-cavity coupling and the dot-phonon interactions are taken into account without approximations. This is achieved by a reformulation of an exact iterative path-integral scheme which is applicable for a large class of quantum-dissipative systems and which in our case reduces the numerical demands by 15 orders of magnitude.

Relaxation and coherent oscillations in the spin dynamics of II-VI diluted magnetic quantum wells

Quantum kinetic equations of motion for the description of the exciton spin dynamics in II-VI diluted magnetic semiconductor quantum wells with laser driving are derived. The model includes the magnetic as well as the nonmagnetic carrier-impurity interaction, the Coulomb interaction, Zeeman terms, and the light-matter coupling, allowing for an explicit treatment of arbitrary excitation pulses. Based on a dynamics-controlled truncation scheme, contributions to the equations of motion up to second order in the generating laser field are taken into account. The correlations between the carrier and the impurity subsystems are treated within the framework of a correlation expansion. For vanishing magnetic field, the Markov limit of the quantum kinetic equations formulated in the exciton basis agrees with existing theories based on Fermis golden rule. For narrow quantum wells excited at the

Nonexponential spin decay in a quantum kinetic description of the D'yakonov-Perel' mechanism mediated by impurity scattering

1s

Extracting many-body correlation energies from absorption spectra of diluted magnetic semiconductors

exciton resonance, numerical quantum kinetic simulations reveal pronounced deviations from the Markovian behavior. In particular, the spin decays initially with approximately half the Markovian rate and a non-monotonic decay in the form of an overshoot of up to

Phonon impact on the dynamics of resonantly excited and hot excitons in diluted magnetic semiconductors.

10\,\%

Path-integral approach for nonequilibrium multitime correlation functions of open quantum systems coupled to Markovian and non-Markovian environments

of the initial spin polarization is predicted.