@article{KimZhangWangetal.2016, author = {Kim, Seonghoon and Zhang, Bo and Wang, Zhaorong and Fischer, Julian and Brodbeck, Sebastian and Kamp, Martin and Schneider, Christian and H{\"o}fling, Sven and Deng, Hui}, title = {Coherent Polariton Laser}, series = {Physical Review X}, volume = {6}, journal = {Physical Review X}, number = {011026}, doi = {10.1103/PhysRevX.6.011026}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-166597}, year = {2016}, abstract = {The semiconductor polariton laser promises a new source of coherent light, which, compared to conventional semiconductor photon lasers, has input-energy threshold orders of magnitude lower. However, intensity stability, a defining feature of a coherent state, has remained poor. Intensity noise many times the shot noise of a coherent state has persisted, attributed to multiple mechanisms that are difficult to separate in conventional polariton systems. The large intensity noise, in turn, limits the phase coherence. Thus, the capability of the polariton laser as a source of coherence light is limited. Here, we demonstrate a polariton laser with shot-noise-limited intensity stability, as expected from a fully coherent state. This stability is achieved by using an optical cavity with high mode selectivity to enforce single-mode lasing, suppress condensate depletion, and establish gain saturation. Moreover, the absence of spurious intensity fluctuations enables the measurement of a transition from exponential to Gaussian decay of the phase coherence of the polariton laser. It suggests large self-interaction energies in the polariton condensate, exceeding the laser bandwidth. Such strong interactions are unique to matter-wave lasers and important for nonlinear polariton devices. The results will guide future development of polariton lasers and nonlinear polariton devices.}, language = {en} } @article{RedlichLingnauHolzingeretal.2016, author = {Redlich, Christoph and Lingnau, Benjamin and Holzinger, Steffen and Schlottmann, Elisabeth and Kreinberg, S{\"o}ren and Schneider, Christian and Kamp, Martin and H{\"o}fling, Sven and Wolters, Janik and Reitzenstein, Stephan and L{\"u}dge, Kathy}, title = {Mode-switching induced super-thermal bunching in quantum-dot microlasers}, series = {New Journal of Physics}, volume = {18}, journal = {New Journal of Physics}, number = {063011}, doi = {10.1088/1367-2630/18/6/063011}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-166286}, year = {2016}, abstract = {The super-thermal photon bunching in quantum-dot (QD) micropillar lasers is investigated both experimentally and theoretically via simulations driven by dynamic considerations. Using stochastic multi-mode rate equations we obtain very good agreement between experiment and theory in terms of intensity profiles and intensity-correlation properties of the examined QD micro-laser's emission. Further investigations of the time-dependent emission show that super-thermal photon bunching occurs due to irregular mode-switching events in the bimodal lasers. Our bifurcation analysis reveals that these switchings find their origin in an underlying bistability, such that spontaneous emission noise is able to effectively perturb the two competing modes in a small parameter region. We thus ascribe the observed high photon correlation to dynamical multistabilities rather than quantum mechanical correlations.}, language = {en} } @article{NitscheKimRoumposetal.2016, author = {Nitsche, Wolfgang H. and Kim, Na Young and Roumpos, Georgios and Schneider, Christian and H{\"o}fling, Sven and Forchel, Alfred and Yamamoto, Yoshihisa}, title = {Spatial correlation of two-dimensional bosonic multimode condensates}, series = {Physical Review A}, volume = {93}, journal = {Physical Review A}, number = {5}, doi = {10.1103/PhysRevA.93.053622}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-188897}, pages = {53622}, year = {2016}, abstract = {The Berezinskii-Kosterlitz-Thouless (BKT) theorem predicts that two-dimensional bosonic condensates exhibit quasi-long-range order which is characterized by a slow decay of the spatial coherence. However previous measurements on exciton-polariton condensates revealed that their spatial coherence can decay faster than allowed under the BKT theory, and different theoretical explanations have already been proposed. Through theoretical and experimental study of exciton-polariton condensates, we show that the fast decay of the coherence can be explained through the simultaneous presence of multiple modes in the condensate.}, language = {en} } @article{LundtKlembtCherotchenkoetal.2016, author = {Lundt, Nils and Klembt, Sebastian and Cherotchenko, Evgeniia and Betzold, Simon and Iff, Oliver and Nalitov, Anton V. and Klaas, Martin and Dietrich, Christof P. and Kavokin, Alexey V. and H{\"o}fling, Sven and Schneider, Christian}, title = {Room-temperature Tamm-plasmon exciton-polaritons with a WSe\(_{2}\) monolayer}, series = {Nature Communications}, volume = {7}, journal = {Nature Communications}, doi = {10.1038/ncomms13328}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-169470}, year = {2016}, abstract = {Solid-state cavity quantum electrodynamics is a rapidly advancing field, which explores the frontiers of light-matter coupling. Metal-based approaches are of particular interest in this field, as they carry the potential to squeeze optical modes to spaces significantly below the diffraction limit. Transition metal dichalcogenides are ideally suited as the active material in cavity quantum electrodynamics, as they interact strongly with light at the ultimate monolayer limit. Here, we implement a Tamm-plasmon-polariton structure and study the coupling to a monolayer of WSe\(_{2}\), hosting highly stable excitons. Exciton-polariton formation at room temperature is manifested in the characteristic energy-momentum dispersion relation studied in photoluminescence, featuring an anti-crossing between the exciton and photon modes with a Rabi-splitting of 23.5 meV. Creating polaritonic quasiparticles in monolithic, compact architectures with atomic monolayers under ambient conditions is a crucial step towards the exploration of nonlinearities, macroscopic coherence and advanced spinor physics with novel, low-mass bosons.}, language = {en} } @article{HeIffLundtetal.2016, author = {He, Yu-Ming and Iff, Oliver and Lundt, Nils and Baumann, Vasilij and Davanco, Marcelo and Srinivasan, Kartik and H{\"o}fling, Sven and Schneider, Christian}, title = {Cascaded emission of single photons from the biexciton in monolayered WSe\(_{2}\)}, series = {Nature Communications}, volume = {7}, journal = {Nature Communications}, doi = {10.1038/ncomms13409}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-169363}, year = {2016}, abstract = {Monolayers of transition metal dichalcogenide materials emerged as a new material class to study excitonic effects in solid state, as they benefit from enormous Coulomb correlations between electrons and holes. Especially in WSe\(_{2}\), sharp emission features have been observed at cryogenic temperatures, which act as single photon sources. Tight exciton localization has been assumed to induce an anharmonic excitation spectrum; however, the evidence of the hypothesis, namely the demonstration of a localized biexciton, is elusive. Here we unambiguously demonstrate the existence of a localized biexciton in a monolayer of WSe\(_{2}\), which triggers an emission cascade of single photons. The biexciton is identified by its time-resolved photoluminescence, superlinearity and distinct polarization in micro-photoluminescence experiments. We evidence the cascaded nature of the emission process in a cross-correlation experiment, which yields a strong bunching behaviour. Our work paves the way to a new generation of quantum optics experiments with two-dimensional semiconductors.}, language = {en} } @article{KochereshkoDurnevBesombesetal.2016, author = {Kochereshko, Vladimir P. and Durnev, Mikhail V. and Besombes, Lucien and Mariette, Henri and Sapega, Victor F. and Askitopoulos, Alexis and Savenko, Ivan G. and Liew, Timothy C. H. and Shelykh, Ivan A. and Platonov, Alexey V. and Tsintzos, Simeon I. and Hatzopoulos, Z. and Savvidis, Pavlos G. and Kalevich, Vladimir K. and Afanasiev, Mikhail M. and Lukoshkin, Vladimir A. and Schneider, Christian and Amthor, Matthias and Metzger, Christian and Kamp, Martin and Hoefling, Sven and Lagoudakis, Pavlos and Kavokin, Alexey}, title = {Lasing in Bose-Fermi mixtures}, series = {Scientific Reports}, volume = {6}, journal = {Scientific Reports}, number = {20091}, doi = {10.1038/srep20091}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-168152}, year = {2016}, abstract = {Light amplification by stimulated emission of radiation, well-known for revolutionising photonic science, has been realised primarily in fermionic systems including widely applied diode lasers. The prerequisite for fermionic lasing is the inversion of electronic population, which governs the lasing threshold. More recently, bosonic lasers have also been developed based on Bose-Einstein condensates of exciton-polaritons in semiconductor microcavities. These electrically neutral bosons coexist with charged electrons and holes. In the presence of magnetic fields, the charged particles are bound to their cyclotron orbits, while the neutral exciton-polaritons move freely. We demonstrate how magnetic fields affect dramatically the phase diagram of mixed Bose-Fermi systems, switching between fermionic lasing, incoherent emission and bosonic lasing regimes in planar and pillar microcavities with optical and electrical pumping. We collected and analyzed the data taken on pillar and planar microcavity structures at continuous wave and pulsed optical excitation as well as injecting electrons and holes electronically. Our results evidence the transition from a Bose gas to a Fermi liquid mediated by magnetic fields and light-matter coupling.}, language = {en} } @article{JahnkeGiesAssmannetal.2016, author = {Jahnke, Frank and Gies, Christopher and Aßmann, Marc and Bayer, Manfred and Leymann, H.A.M. and Foerster, Alexander and Wiersig, Jan and Schneider, Christian and Kamp, Martin and H{\"o}fling, Sven}, title = {Giant photon bunching, superradiant pulse emission and excitation trapping in quantum-dot nanolasers}, series = {Nature Communications}, volume = {7}, journal = {Nature Communications}, number = {11540}, doi = {10.1038/ncomms11540}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-166144}, year = {2016}, abstract = {Light is often characterized only by its classical properties, like intensity or coherence. When looking at its quantum properties, described by photon correlations, new information about the state of the matter generating the radiation can be revealed. In particular the difference between independent and entangled emitters, which is at the heart of quantum mechanics, can be made visible in the photon statistics of the emitted light. The well-studied phenomenon of superradiance occurs when quantum-mechanical correlations between the emitters are present. Notwithstanding, superradiance was previously demonstrated only in terms of classical light properties. Here, we provide the missing link between quantum correlations of the active material and photon correlations in the emitted radiation. We use the superradiance of quantum dots in a cavity-quantum electrodynamics laser to show a direct connection between superradiant pulse emission and distinctive changes in the photon correlation function. This directly demonstrates the importance of quantum-mechanical correlations and their transfer between carriers and photons in novel optoelectronic devices.}, language = {en} }