@article{WinklerFischerSchadeetal.2015,
  author    = {Winkler, Karol and Fischer, Julian and Schade, Anne and Amthor, Matthias and Dall, Robert and Geßler, Jonas and Emmerling, Monika and Ostrovskaya, Elena A. and Kamp, Martin and Schneider, Christian and H{\"o}fling, Sven},
  title     = {A polariton condensate in a photonic crystal potential landscape},
  series = {New Journal of Physics},
  volume    = {17},
  journal   = {New Journal of Physics},
  doi       = {10.1088/1367-2630/17/2/023001},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-125050},
  pages     = {023001},
  year      = {2015},
  abstract  = {The possibility of investigating macroscopic coherent quantum states in polariton condensates and of engineering polariton landscapes in semiconductors has triggered interest in using polaritonic systems to simulate complex many-body phenomena. However, advanced experiments require superior trapping techniques that allow for the engineering of periodic and arbitrary potentials with strong on-site localization, clean condensate formation, and nearest-neighbor coupling. Here we establish a technology that meets these demands and enables strong, potentially tunable trapping without affecting the favorable polariton characteristics. The traps are based on a locally elongated microcavity which can be formed by standard lithography. We observe polariton condensation with non-resonant pumping in single traps and photonic crystal square lattice arrays. In the latter structures, we observe pronounced energy bands, complete band gaps, and spontaneous condensation at the M-point of the Brillouin zone.},
  language  = {en}
}
@article{OPUS4-13985,
  title     = {Centrality and rapidity dependence of inclusive jet production in \(\sqrt{^SNN}\)=5.02 TeV proton-lead collisions with the ATLAS detector},
  series = {Physics Letters B},
  volume    = {748},
  journal   = {Physics Letters B},
  organization    = {ATLAS Collaboration},
  doi       = {10.1016/j.physletb.2015.07.023},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-139857},
  pages     = {392-413},
  year      = {2015},
  abstract  = {Measurements of the centrality and rapidity dependence of inclusive jet production in \(\sqrt{^SNN}\)=5.02 TeV proton-lead (p+Pb) collisions and the jet cross-section in \(\sqrt{s}\)=2.76 TeV proton-proton collisions are presented. These quantities are measured in datasets corresponding to an integrated luminosity of 27.8 nb\(^{-1}\) and 4.0 pb\(^{-1}\), respectively, recorded with the ATLAS detector at the Large Hadron Collider in 2013. The p+Pb collision centrality was characterised using the total transverse energy measured in the pseudorapidity interval -4.9<η<-3.2 in the direction of the lead beam. Results are presented for the double-differential per-collision yields as a function of jet rapidity and transverse momentum (\(p_T\)) for minimum-bias and centrality-selected p+Pb collisions, and are compared to the jet rate from the geometric expectation. The total jet yield in minimum-bias events is slightly enhanced above the expectation in a \(p_T\)-dependent manner but is consistent with the expectation within uncertainties. The ratios of jet spectra from different centrality selections show a strong modification of jet production at all \(p_T\) at forward rapidities and for large \(p_T\) at mid-rapidity, which manifests as a suppression of the jet yield in central events and an enhancement in peripheral events. These effects imply that the factorisation between hard and soft processes is violated at an unexpected level in proton-nucleus collisions. Furthermore, the modifications at forward rapidities are found to be a function of the total jet energy only, implying that the violations may have a simple dependence on the hard parton-parton kinematics.},
  language  = {en}
}
@article{OPUS4-14961,
  title     = {Constraints on the off-shell Higgs boson signal strength in the high-mass ZZ and WW final states with the ATLAS detector},
  series = {European Physical Journal C: Particles and Fields},
  volume    = {75},
  journal   = {European Physical Journal C: Particles and Fields},
  number    = {7},
  organization    = {ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-015-3542-2},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-149615},
  pages     = {335},
  year      = {2015},
  abstract  = {Measurements of the ZZ and WW final states in the mass range above the 2m\(_Z\) and 2m\(_W\) thresholds provide a unique opportunity to measure the off-shell coupling strength of the Higgs boson. This paper presents constraints on the off-shell Higgs boson event yields normalised to the Standard Model prediction (signal strength) in the ZZ→4ℓ, ZZ→2ℓ2ν and WW→eνμν final states. The result is based on pp collision data collected by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 20.3 fb\(^{-1}\) at a collision energy of \(\sqrt {s}\)=8 TeV. Using the CL\(_S\) method, the observed 95 \% confidence level (CL) upper limit on the off-shell signal strength is in the range 5.1-8.6, with an expected range of 6.7-11.0. In each case the range is determined by varying the unknown gg→ZZ and gg→WW background K-factor from higher-order quantum chromodynamics corrections between half and twice the value of the known signal K-factor. Assuming the relevant Higgs boson couplings are independent of the energy scale of the Higgs boson production, a combination with the on-shell measurements yields an observed (expected) 95 \% CL upper limit on Γ\(_H\)/Γ\(^{SM}_{H}\) in the range 4.5-7.5 (6.5-11.2) using the same variations of the background K-factor. Assuming that the unknown gg→VV background K-factor is equal to the signal K-factor, this translates into an observed (expected) 95 \% CL upper limit on the Higgs boson total width of 22.7 (33.0) MeV.},
  language  = {en}
}
@article{OPUS4-14963,
  title     = {Determination of spin and parity of the Higgs boson in the WW\(^{*}\)→eνμν decay channel with the ATLAS detector},
  series = {European Physical Journal C: Particles and Fields},
  volume    = {75},
  journal   = {European Physical Journal C: Particles and Fields},
  number    = {5},
  organization    = {ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-015-3436-3},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-149632},
  pages     = {231},
  year      = {2015},
  abstract  = {Studies of the spin and parity quantum numbers of the Higgs boson in the WW\(^{*}\)→eνμν final state are presented, based on proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb\(^{-1}\) at a centre-of-mass energy of \(\sqrt {s}\)=8 TeV. The Standard Model spin-parity J\(^{CP}\)=0\(^{++}\) hypothesis is compared with alternative hypotheses for both spin and CP. The case where the observed resonance is a mixture of the Standard-Model-like Higgs boson and CP-even (J\(^{CP}\)=0\(^{++}\)) or CP-odd (J\(^{CP}\)=0\(^{+-}\)) Higgs boson in scenarios beyond the Standard Model is also studied. The data are found to be consistent with the Standard Model prediction and limits are placed on alternative spin and CP hypotheses, including CP mixing in different scenarios.},
  language  = {en}
}
@article{SessiSilkinNechaevetal.2015,
  author    = {Sessi, Paolo and Silkin, Vyacheslav M. and Nechaev, Ilya A. and Bathon, Thomas and El-Kareh, Lydia and Chulkov, Evgueni V. and Echenique, Pedro M. and Bode, Matthias},
  title     = {Direct observation of many-body charge density oscillations in a two-dimensional electron gas},
  series = {Nature Communications},
  volume    = {6},
  journal   = {Nature Communications},
  number    = {8691},
  doi       = {10.1038/ncomms9691},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-145246},
  year      = {2015},
  abstract  = {Quantum interference is a striking manifestation of one of the basic concepts of quantum mechanics: the particle-wave duality. A spectacular visualization of this effect is the standing wave pattern produced by elastic scattering of surface electrons around defects, which corresponds to a modulation of the electronic local density of states and can be imaged using a scanning tunnelling microscope. To date, quantum-interference measurements were mainly interpreted in terms of interfering electrons or holes of the underlying band-structure description. Here, by imaging energy-dependent standing-wave patterns at noble metal surfaces, we reveal, in addition to the conventional surface-state band, the existence of an 'anomalous' energy band with a well-defined dispersion. Its origin is explained by the presence of a satellite in the structure of the many-body spectral function, which is related to the acoustic surface plasmon. Visualizing the corresponding charge oscillations provides thus direct access to many-body interactions at the atomic scale.},
  language  = {en}
}
@article{LeeLimSchneideretal.2015,
  author    = {Lee, Chang-Min and Lim, Hee-Jin and Schneider, Christian and Maier, Sebastian and H{\"o}fling, Sven and Kamp, Martin and Lee, Yong-Hee},
  title     = {Efficient single photon source based on \(\mu\)-fibre-coupled tunable microcavity},
  series = {Scientific Reports},
  volume    = {5},
  journal   = {Scientific Reports},
  number    = {14309},
  doi       = {10.1038/srep14309},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-145835},
  year      = {2015},
  abstract  = {Efficient and fast on-demand single photon sources have been sought after as critical components of quantum information science. We report an efficient and tunable single photon source based on an InAs quantum dot (QD) embedded in a photonic crystal cavity coupled with a highly curved \(\mu\)-fibre. Exploiting evanescent coupling between the \(\mu\)-fibre and the cavity, a high collection efficiency of 23\% and Purcell-enhanced spontaneous emissions are observed. In our scheme, the spectral position of a resonance can be tuned by as much as 1.5 nm by adjusting the contact position of the \(\mu\)-fibre, which increases the spectral coupling probability between the QD and the cavity mode. Taking advantage of the high photon count rate and the tunability, the collection efficiencies and the decay rates are systematically investigated as a function of the QD-cavity detuning.},
  language  = {en}
}
@article{FuchsStenderTrupkeetal.2015,
  author    = {Fuchs, F. and Stender, B. and Trupke, M. and Simin, D. and Pflaum, J. and Dyakonov, V. and Astakhov, G.V.},
  title     = {Engineering near-infrared single-photon emitters with optically active spins in ultrapure silicon carbide},
  series = {Nature Communications},
  volume    = {6},
  journal   = {Nature Communications},
  number    = {7578},
  doi       = {10.1038/ncomms8578},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-148502},
  year      = {2015},
  abstract  = {Vacancy-related centres in silicon carbide are attracting growing attention because of their appealing optical and spin properties. These atomic-scale defects can be created using electron or neutron irradiation; however, their precise engineering has not been demonstrated yet. Here, silicon vacancies are generated in a nuclear reactor and their density is controlled over eight orders of magnitude within an accuracy down to a single vacancy level. An isolated silicon vacancy serves as a near-infrared photostable single-photon emitter, operating even at room temperature. The vacancy spins can be manipulated using an optically detected magnetic resonance technique, and we determine the transition rates and absorption cross-section, describing the intensity-dependent photophysics of these emitters. The on-demand engineering of optically active spins in technologically friendly materials is a crucial step toward implementation of both maser amplifiers, requiring high-density spin ensembles, and qubits based on single spins.},
  language  = {en}
}
@article{OPUS4-14982,
  title     = {Identification and energy calibration of hadronically decaying tau leptons with the ATLAS experiment in pp collisions at \(\sqrt {s}\)=8 TeV},
  series = {European Physical Journal C: Particles and Fields},
  volume    = {75},
  journal   = {European Physical Journal C: Particles and Fields},
  number    = {7},
  organization    = {ATLAS Collaboration},
  doi       = {10.1140/epjc/s10052-015-3500-z},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-149829},
  pages     = {303},
  year      = {2015},
  abstract  = {This paper describes the trigger and offline reconstruction, identification and energy calibration algorithms for hadronic decays of tau leptons employed for the data collected from pp collisions in 2012 with the ATLAS detector at the LHC center-of-mass energy \(\sqrt {s}\)=8 TeV. The performance of these algorithms is measured in most cases with Z decays to tau leptons using the full 2012 dataset, corresponding to an integrated luminosity of 20.3 fb\(^{-1}\). An uncertainty on the offline reconstructed tau energy scale of 2-4 \%, depending on transverse energy and pseudorapidity, is achieved using two independent methods. The offline tau identification efficiency is measured with a precision of 2.5 \% for hadronically decaying tau leptons with one associated track, and of 4 \% for the case of three associated tracks, inclusive in pseudorapidity and for a visible transverse energy greater than 20 GeV. For hadronic tau lepton decays selected by offline algorithms, the tau trigger identification efficiency is measured with a precision of 2-8 \%, depending on the transverse energy. The performance of the tau algorithms, both offline and at the trigger level, is found to be stable with respect to the number of concurrent proton-proton interactions and has supported a variety of physics results using hadronically decaying tau leptons at ATLAS.},
  language  = {en}
}
@article{CharnukhaThirupathaiahZabolotnyyetal.2015,
  author    = {Charnukha, A. and Thirupathaiah, S. and Zabolotnyy, V. B. and B{\"u}chner, B. and Zhigadlo, N. D. and Batlogg, B. and Yaresko, A. N. and Borisenko, S. V.},
  title     = {Interaction-induced singular Fermi surface in a high-temperature oxypnictide superconductor},
  series = {Scientific Reports},
  volume    = {5},
  journal   = {Scientific Reports},
  number    = {10392},
  doi       = {10.1038/srep10392},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-151987},
  year      = {2015},
  abstract  = {In the family of iron-based superconductors, LaFeAsO-type materials possess the simplest electronic structure due to their pronounced two-dimensionality. And yet they host superconductivity with the highest transition temperature T\(_{c}\)\(\approx\)55K. Early theoretical predictions of their electronic structure revealed multiple large circular portions of the Fermi surface with a very good geometrical overlap (nesting), believed to enhance the pairing interaction and thus superconductivity. The prevalence of such large circular features in the Fermi surface has since been associated with many other iron-based compounds and has grown to be generally accepted in the field. In this work we show that a prototypical compound of the 1111-type, SmFe\(_{0.92}\)Co\(_{0.08}\)AsO, is at odds with this description and possesses a distinctly different Fermi surface, which consists of two singular constructs formed by the edges of several bands, pulled to the Fermi level from the depths of the theoretically predicted band structure by strong electronic interactions. Such singularities dramatically affect the low-energy electronic properties of the material, including superconductivity. We further argue that occurrence of these singularities correlates with the maximum superconducting transition temperature attainable in each material class over the entire family of iron-based superconductors.},
  language  = {en}
}
@article{MotykaSękRyczkoetal.2015,
  author    = {Motyka, Marcin and Sęk, Grzegorz and Ryczko, Krzysztof and Dyksik, Mateusz and Weih, Robert and Patriarche, Gilles and Misiewicz, Jan and Kamp, Martin and H{\"o}fling, Sven},
  title     = {Interface Intermixing in Type II InAs/GaInAsSb Quantum Wells Designed for Active Regions of Mid-Infrared-Emitting Interband Cascade Lasers},
  series = {Nanoscale Research Letters},
  volume    = {10},
  journal   = {Nanoscale Research Letters},
  number    = {471},
  doi       = {10.1186/s11671-015-1183-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-136386},
  year      = {2015},
  abstract  = {The effect of interface intermixing in W-design GaSb/AlSb/InAs/Ga\(_{0.665}\)In\(_{0.335}\)As\(_x\)Sb\(_{1-x}\)/InAs/AlSb/GaSb quantum wells (QWs) has been investigated by means of optical spectroscopy supported by structural data and by band structure calculations. The fundamental optical transition has been detected at room temperature through photoluminescence and photoreflectance measurements and appeared to be blueshifted with increasing As content of the GaInAsSb layer, in contrast to the energy-gap-driven shifts calculated for an ideally rectangular QW profile. The arsenic incorporation into the hole-confining layer affects the material and optical structure also altering the InAs/GaInAsSb interfaces and their degree of intermixing. Based on the analysis of cross-sectional transmission electron microscopy images and energy-dispersive X-ray spectroscopy, we could deduce the composition distribution across the QW layers and hence simulate more realistic confinement potential profiles. For such smoothed interfaces that indicate As-enhanced intermixing, the energy level calculations have been able to reproduce the experimentally obtained trend.},
  language  = {en}
}