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L. Schneebeli

Bio: L. Schneebeli is an academic researcher from University of Marburg. The author has contributed to research in topics: Exciton & Terahertz radiation. The author has an hindex of 5, co-authored 12 publications receiving 161 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, the second-rung resonance of the Jaynes-Cummings ladder was analyzed and optimum excitation conditions were determined using a microscopic theory, and the computed photon-statistics spectrum displays gigantic, experimentally robust resonances at the energetic positions of the second rung emission.
Abstract: It is shown that spectrally resolved photon-statistics measurements of the resonance fluorescence from realistic semiconductor quantum-dot systems allow for high contrast identification of the two-photon strong-coupling states. Using a microscopic theory, the second-rung resonance of Jaynes-Cummings ladder is analyzed and optimum excitation conditions are determined. The computed photon-statistics spectrum displays gigantic, experimentally robust resonances at the energetic positions of the second-rung emission.

58 citations

Journal ArticleDOI
TL;DR: Terahertz pulses are used to induce resonant transitions between the eigenstates of optically generated exciton populations in a high-quality semiconductor quantum well sample, yielding an effective terahertz transition between the 1s and 2s populations.
Abstract: We use terahertz pulses to induce resonant transitions between the eigenstates of optically generated exciton populations in a high-quality semiconductor quantum well sample. Monitoring the excitonic photoluminescence, we observe transient quenching of the $1s$ exciton emission, which we attribute to the terahertz-induced $1s$-to-$2p$ excitation. Simultaneously, a pronounced enhancement of the $2s$ exciton emission is observed, despite the $1s$-to-$2s$ transition being dipole forbidden. A microscopic many-body theory explains the experimental observations as a Coulomb-scattering mixing of the $2s$ and $2p$ states, yielding an effective terahertz transition between the $1s$ and $2s$ populations.

29 citations

Journal ArticleDOI
TL;DR: It is shown that spectrally resolved photon-statistics measurements of the resonance fluorescence from realistic semiconductor quantum-dot systems allow for high contrast identification of the two-photon strong-coupling states.
Abstract: Maxwell-Bloch and luminescence equations are presented which describe vacuum Rabi splitting and the quantum rungs on the Jaynes-Cummings ladder for strongly-coupled dot-cavity systems. Resonance fluorescence conditions are considered where an optical pump is exciting the dot-cavity system while the re-emitted light is detected. An analytical formula for the vacuum Rabi splitting is derived and a pumping mechanism for the direct generation of the second rung is presented and analyzed. An optimum pumping frequency and optimum pumping intensity are identified for the generation of the second rung. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

13 citations

Journal ArticleDOI
TL;DR: In this paper, a microscopic theory is developed to analyze the results of time-resolved terahertz quenching studies of the magnetoexcitonic photoluminescence from GaAs/AlGaAs quantum wells.
Abstract: Time-resolved terahertz quenching studies of the magnetoexcitonic photoluminescence from GaAs/AlGaAs quantum wells are performed. A microscopic theory is developed to analyze the experiments. Detailed experiment-theory comparisons reveal a remarkable magnetic-field controllability of the Coulomb and terahertz interactions in the excitonic system.

7 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, a many-body theory based on an equation-of-motion approach for the interacting electron, hole, photon, and phonon system is reviewed, and the infinite hierarchy of coupled equations for the relevant correlation functions is systematically truncated using a cluster-expansion scheme.

373 citations

Journal ArticleDOI
TL;DR: In this paper, the authors observed a continuous change in photon correlations from strong antibunching to bunching by tuning either the probe laser or the cavity mode frequency, which is explained by the photon blockade and tunnelling in the anharmonic Jaynes-Cummings model.
Abstract: Researchers observe a continuous change in photon correlations from strong antibunching to bunching by tuning either the probe laser or the cavity mode frequency. These results, which demonstrate unprecedented strong single-photon nonlinearities in quantum dot cavity system, are explained by the photon blockade and tunnelling in the anharmonic Jaynes–Cummings model.

324 citations

Journal ArticleDOI
21 Oct 2019-Nature
TL;DR: A gated, ultralow-loss, frequency-tunable microcavity device that establishes a route to the development of semiconductor-based quantum photonics, such as single-photon sources and photon–photon gates.
Abstract: The strong-coupling regime of cavity quantum electrodynamics (QED) represents the light–matter interaction at the fully quantum level. Adding a single photon shifts the resonance frequencies—a profound nonlinearity. Cavity QED is a test bed for quantum optics1–3 and the basis of photon–photon and atom–atom entangling gates4,5. At microwave frequencies, cavity QED has had a transformative effect6, enabling qubit readout and qubit couplings in superconducting circuits. At optical frequencies, the gates are potentially much faster; the photons can propagate over long distances and can be easily detected. Following pioneering work on single atoms1–3,7, solid-state implementations using semiconductor quantum dots are emerging8–15. However, miniaturizing semiconductor cavities without introducing charge noise and scattering losses remains a challenge. Here we present a gated, ultralow-loss, frequency-tunable microcavity device. The gates allow both the quantum dot charge and its resonance frequency to be controlled electrically. Furthermore, cavity feeding10,11,13–17, the observation of the bare-cavity mode even at the quantum dot–cavity resonance, is eliminated. Even inside the microcavity, the quantum dot has a linewidth close to the radiative limit. In addition to a very pronounced avoided crossing in the spectral domain, we observe a clear coherent exchange of a single energy quantum between the ‘atom’ (the quantum dot) and the cavity in the time domain (vacuum Rabi oscillations), whereas decoherence arises mainly via the atom and photon loss channels. This coherence is exploited to probe the transitions between the singly and doubly excited photon–atom system using photon-statistics spectroscopy18. The work establishes a route to the development of semiconductor-based quantum photonics, such as single-photon sources and photon–photon gates. Strong coupling between a gated semiconductor quantum dot and an optical microcavity is observed in an ultralow-loss frequency-tunable microcavity device.

172 citations

Journal ArticleDOI
TL;DR: The large exciton binding energy in MoS2 enables two distinctly different excitation methods: above-band gap excitation and quasi-resonant excitation of excitonic resonances below the single-particle band gap.
Abstract: We discuss the photoluminescence (PL) of semiconducting transition metal dichalcogenides on the basis of experiments and a microscopic theory The latter connects ab initio calculations of the single-particle states and Coulomb matrix elements with a many-body description of optical emission spectra For monolayer MoS2, we study the PL efficiency at the excitonic A and B transitions in terms of carrier populations in the band structure and provide a quantitative comparison to an (In)GaAs quantum well-structure Suppression and enhancement of PL under biaxial strain is quantified in terms of changes in the local extrema of the conduction and valence bands The large exciton binding energy in MoS2 enables two distinctly different excitation methods: above-band gap excitation and quasi-resonant excitation of excitonic resonances below the single-particle band gap The latter case creates a nonequilibrium distribution of carriers predominantly in the K-valleys, which leads to strong emission from the A-exciton transition and a visible B-peak even if the band gap is indirect For above-band gap excitation, we predict a strongly reduced emission intensity at comparable carrier densities and the absence of B-exciton emission The results agree well with PL measurements performed on monolayer MoS2 at excitation wavelengths of 405 nm (above) and 532 nm (below the band gap)

171 citations

Journal ArticleDOI
TL;DR: In this article, the authors introduce a semiconductor theory, originating from a microscopic Hamiltonian, to describe lasing from quantum dots embedded in microcavities, which includes modified contributions of spontaneous and stimulated emission as well as many-body effects.
Abstract: When it comes to laser phenomena in quantum-dot-based systems, usually atomic models are employed to analyze the characteristic behavior. We introduce a semiconductor theory, originating from a microscopic Hamiltonian, to describe lasing from quantum dots embedded in microcavities. The theory goes beyond two-level atomic models and includes modified contributions of spontaneous and stimulated emission as well as many-body effects. An extended version, which incorporates carrier-photon correlations, provides direct access to the photon autocorrelation function and thereby on the statistical properties of the laser emission. In comparison to atomic models, we find deviations in the dependence of the input/output curve on the spontaneous emission coupling $\ensuremath{\beta}$. Modifications of the photon statistics are discussed for high-quality microcavities with a small number of emitters.

166 citations