H. Stolz

Excitonic photoluminescence in semiconductor quantum wells: plasma versus excitons.

Time-resolved photoluminescence spectra after nonresonant excitation show a distinct 1s resonance, independent of the existence of bound excitons. A microscopic analysis identifies exciton and electron-hole plasma contributions. For low temperatures and low densities, the excitonic emission is extremely sensitive to details of the electron-hole-pair population making it possible to identify even minute fractions of optically active excitons.

Many-body dynamics and exciton formation studied by time-resolved photoluminescence

The dynamics of exciton and electron-hole plasma populations is studied via time-resolved photoluminescence after nonresonant excitation. By comparing the peak emission at the exciton resonance with the emission of the continuum, it is possible to experimentally identify regimes where the emission originates predominantly from exciton and/or plasma populations. The results are supported by a microscopic theory which allows one to extract the fraction of bright excitons as a function of time.

Deviations of the exciton level spectrum in cuprous oxide from the hydrogen series

Recent high-resolution absorption spectroscopy on excited excitons in cuprous oxide [Nature (London) 514, 343 (2014)] has revealed significant deviations of their spectrum from that of the ideal hydrogen-like series. Here we show that the complex band dispersion of the crystal, which determines the kinetic energy of electrons and holes, strongly affects the exciton binding energy. Specifically, we show that the nonparabolicity of the band dispersion is the main cause of the deviation from the hydrogen series. Experimental data collected from high-resolution absorption spectroscopy in electric fields validate the assignment of the deviation to the nonparabolicity of the band dispersion.

Signatures of Quantum Coherences in Rydberg Excitons.

Coherent optical control of individual particles has been demonstrated both for atoms and semiconductor quantum dots. Here we demonstrate the emergence of quantum coherent effects in semiconductor Rydberg excitons in bulk Cu_{2}O. Because of the spectral proximity between two adjacent Rydberg exciton states, a single-frequency laser may pump both resonances with little dissipation from the detuning. As a consequence, additional resonances appear in the absorption spectrum that correspond to dressed states consisting of two Rydberg exciton levels coupled to the excitonic vacuum, forming a V-type three-level system, but driven only by one laser light source. We show that the level of pure dephasing in this system is extremely low. These observations are a crucial step towards coherently controlled quantum technologies in a bulk semiconductor.

Characterization of disorder in semiconductors via single-photon interferometry

The method of angular photonic correlations of spontaneous emission is introduced as an experimental, purely optical scheme to characterize disorder in semiconductor nanostructures. The theoretical expression for the angular correlations is derived and numerically evaluated for a model system. The results demonstrate how the proposed experimental method yields direct information about the spatial distribution of the relevant states and thus on the disorder present in the system.

Wave-vector-dependent exchange interaction and its relevance for the effective exciton mass in Cu2O

The wave-vector dependence of electron-hole exchange interaction is investigated. For the yellow 1S exciton in

Absorption and emission of polariton modes in a ZnSe–ZnSSe heterostructure

{mathrm{Cu}}_{2}mathrm{O}

Exciton/plasma fraction from photoluminescence

the exchange is derived up to the order

Wave-Vector-Dependent Exciton Exchange Interaction

{k}^{2}

Entanglement between a Photon and a Quantum Well

. The theoretical predictions are verified experimentally by high-resolution absorption experiments. In agreement with theory the fine structure shows a characteristic dependence on the direction of the wave vector. The exchange splitting of the orthoexciton triplet are distinguished from strain-induced perturbations. The exchange gives rise to an isotropic and an anisotropic correction of the effective exciton mass. This can explain the discrepancies in the measurements of the exciton mass in