@article{BeckerHeEinfeldtetal.1993,
  author    = {Becker, Charles R. and He, L. and Einfeldt, S. and Wu, Y. S. and L{\´e}rondel, G. and Heinke, H. and Oehling, S. and Bicknell-Tassius, R. N. and Landwehr, G.},
  title     = {Molecular beam epitaxial growth and characterization of (100) HgSe on GaAs},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-50947},
  year      = {1993},
  abstract  = {In this paper, we present results on the first MBE growth of HgSe. The influence of the GaAs substrate temperature as well as the Hg and Se fluxes on the growth and the electrical properties has been investigated. It has been found that the growth rate is very low at substrate temperatures above 120°C. At 120°C and at lower temperatures, the growth rate is appreciably higher. The sticking coefficient of Se seems to depend inversely on the Hg/Se flux ratio. Epitaxial growth could be maintained at 70°C with Hg/Se flux ratios between lOO and ISO, and at 160°C between 280 and 450. The electron mobilities of these HgSe epilayers at room temperature decrease from a maximum value of 8.2 x 10^3 cm2 /V' s with increasing electron concentration. The concentration was found to be between 6xlO^17 and 1.6x10^19 cm- 3 at room temperature. Rocking curves from X-ray diffraction measurements of the better epilayers have a full width at half maximum of 5S0 arc sec.},
  subject      = {Physik},
  language  = {en}
}
@article{BeckerLatussekHeinkeetal.1993,
  author    = {Becker, Charles, R. and Latussek, V. and Heinke, H. and Regnet, M. M. and Goschenhofer, F. and Einfeldt, S. and He, L. and Bangert, E. and Kraus, M. M. and Landwehr, G.},
  title     = {Molecular beam epitaxial growth and characterization of (001) Hg\(_{1-x}\) Cd\(_x\) Te-HgTe superlattices},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-50959},
  year      = {1993},
  abstract  = {The molecular beam epitaxially growth of (001) Hg\(_{1-x}\) Cd\(_z\) Te-HgTe superlattices has been systematically investigated. The well width as well as the period were determined directly by X-ray diffraction. This was accomphshed for the well width by exploiting the high reflectivity from HgTe and the low reflectivity from CdTe for the (002) Bragg reflection. Knowing the well and barrier thicknesses we have been able to set an upper limit on the aver~ge composition of the barriers, Xl, by annealing the superlattice and then measuring the composition of the. resultmg alloy. Xb was shown to decrease exponentially with decreasing barrier width. Xb is appreciably smaller m. narrow barriers due to the increased significance of interdiffusion in the Hg\(_{1-x}\)Cd\(_x\) Te/HgTe interface in narrow barriers. The experimentally determined optical absorption coefficient for these superlattices is compared WIth theoretical calculations. The absorption coefficient was determined from transmission and reflection spectra at 300, 77 and 5 K. Using the thickness and composition of the barriers and wells, and an interface width due to interdiffusion, the complex refractive index is calculated and compared with the experimental absorption coefficient. The envelope function method based on an 8 x 8 second order k . p band model was used to calculate the superlattice states. These results when inserted into Kubo's formula, yield the dynamic conductivity for interband transitions. The experimental and theoretical values for the absorption coefficient using no adjustable parameters are in good agreement for most of the investigated superlattices. Furthermore the agreement for the higher energetic interband transitions is much worse if values for the barrier composition, which are appreciably different than the experimentally determined values, are used. The infrared photoluminescence was investigated at temperatures from 4.2 to 300 K. Pronounced photoluminescence was observed for all superlattices in this temperature range.},
  subject      = {Physik},
  language  = {en}
}
@article{DeciusBeckerFredericks1972,
  author    = {Decius, J. C. and Becker, Charles R. and Fredericks, W. J.},
  title     = {Force constants of the metaborate ion in alkali halides},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-50935},
  year      = {1972},
  abstract  = {No abstract available},
  subject      = {Physik},
  language  = {en}
}
@article{JanottaGogolinBarrettetal.2011,
  author    = {Janotta, Peter and Gogolin, Christian and Barrett, Jonathan and Brunner, Nicolas},
  title     = {Limits on nonlocal correlations from the structure of the local state space},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-75003},
  year      = {2011},
  abstract  = {The outcomes of measurements on entangled quantum systems can be nonlocally correlated. However, while it is easy to write down toy theories allowing arbitrary nonlocal correlations, those allowed in quantum mechanics are limited. Quantum correlations cannot, for example, violate a principle known as macroscopic locality, which implies that they cannot violate Tsirelson's bound. This paper shows that there is a connection between the strength of nonlocal correlations in a physical theory and the structure of the state spaces of individual systems. This is illustrated by a family of models in which local state spaces are regular polygons, where a natural analogue of a maximally entangled state of two systems exists. We characterize the nonlocal correlations obtainable from such states. The family allows us to study the transition between classical, quantum and super-quantum correlations by varying only the local state space. We show that the strength of nonlocal correlations—in particular whether the maximally entangled state violates Tsirelson's bound or not— depends crucially on a simple geometric property of the local state space, known as strong self-duality. This result is seen to be a special case of a general theorem, which states that a broad class of entangled states in probabilistic theories—including, by extension, all bipartite classical and quantum states— cannot violate macroscopic locality. Finally, our results show that models exist that are locally almost indistinguishable from quantum mechanics, but can nevertheless generate maximally nonlocal correlations.},
  subject      = {Physik},
  language  = {en}
}
@article{KaiserRiemerKnopf2011,
  author    = {Kaiser, J. C. and Riemer, N. and Knopf, D. A.},
  title     = {Detailed heterogeneous oxidation of soot surfaces in a particle-resolved aerosol model},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-75440},
  year      = {2011},
  abstract  = {Using the particle-resolved aerosol model PartMC-MOSAIC, we simulate the heterogeneous oxidation of a monolayer of polycyclic aromatic hydrocarbons (PAHs) on soot particles in an urban atmosphere. We focus on the interaction of the major atmospheric oxidants (O3, NO2, OH, and NO3) with PAHs and include competitive co-adsorption of water vapour for a range of atmospheric conditions. For the first time detailed heterogeneous chemistry based on the P¨oschl-Rudich-Ammann (PRA) framework is modelled on soot particles with a realistic size distribution and a continuous range of chemical ages. We find PAH half-lives, 1/2, on the order of seconds during the night, when the PAHs are rapidly oxidised by the gas-surface reaction with NO3. During the day, 1/2 is on the order of minutes and determined mostly by the surface layer reaction of PAHs with adsorbed O3. Such short half-lives of surface-bound PAHs may lead to efficient conversion of hydrophobic soot into more hygroscopic particles, thus increasing the particles' aerosol-cloud interaction potential. Despite its high reactivity OH appears to have a negligible effect on PAH degradation which can be explained by its very low concentration in the atmosphere. An increase of relative humidity (RH) from 30\% to 80\% increases PAH half-lives by up to 50\%for daytime degradation and by up to 100\% or more for nighttime degradation. Uptake coefficients, averaged over the particle population, are found to be relatively constant over time for O3 (2×10-7 to 2×10-6) and NO2 (5×10-6 to 10-5) at the different levels of NOx emissions and RH considered in this study. In contrast, those for OH and NO3 depend strongly on the surface concentration of PAHs. We do not find a significant influence of heterogeneous reactions on soot particles on the gas phase composition. The derived half-lives of surfacebound PAHs and the time and particle population averaged uptake coefficients for O3 and NO2 presented in this paper can be used as parameterisations for the treatment of heterogeneous chemistry in large-scale atmospheric chemistry models.},
  subject      = {Physik},
  language  = {en}
}
@article{RotheReinthalerLiuetal.2010,
  author    = {Rothe, D. G. and Reinthaler, R. W. and Liu, C-X and Molenkamp, L. W. and Zhang, S-C and Hankiewicz, E. M.},
  title     = {Fingerprint of different spin-orbit terms for spin transport in HgTe quantum wells},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-68362},
  year      = {2010},
  abstract  = {Using k · p theory, we derive an effective four-band model describing the physics of the typical two-dimensional topological insulator (HgTe/CdTe quantum well (QW)) in the presence of an out-of-plane (in the z-direction) inversion breaking potential and an in-plane potential. We find that up to third order in perturbation theory, only the inversion breaking potential generates new elements to the four-band Hamiltonian that are off-diagonal in spin space. When this new effective Hamiltonian is folded into an effective twoband model for the conduction (electron) or valence (heavy hole) bands, two competing terms appear: (i) a Rashba spin-orbit interaction originating from inversion breaking potential in the z-direction and (ii) an in-plane Pauli term as a consequence of the in-plane potential. Spin transport in the conduction band is further analysed within the Landauer-B{\"u}ttiker formalism. We find that for asymmetrically doped HgTe QWs, the behaviour of the spin-Hall conductance is dominated by the Rashba term.},
  subject      = {Physik},
  language  = {en}
}
@article{SchenkelUhlemann2010,
  author    = {Schenkel, Alexander and Uhlemann, Christoph F.},
  title     = {Field Theory on Curved Noncommutative Spacetimes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-68648},
  year      = {2010},
  abstract  = {We study classical scalar field theories on noncommutative curved spacetimes. Following the approach of Wess et al. [Classical Quantum Gravity 22 (2005), 3511 and Classical Quantum Gravity 23 (2006), 1883], we describe noncommutative spacetimes by using (Abelian) Drinfel'd twists and the associated ?-products and ?-differential geometry. In particular, we allow for position dependent noncommutativity and do not restrict ourselves to the Moyal-Weyl deformation. We construct action functionals for real scalar fields on noncommutative curved spacetimes, and derive the corresponding deformed wave equations. We provide explicit examples of deformed Klein-Gordon operators for noncommutative Minkowski, de Sitter, Schwarzschild and Randall-Sundrum spacetimes, which solve the noncommutative Einstein equations. We study the construction of deformed Green's functions and provide a diagrammatic approach for their perturbative calculation. The leading noncommutative corrections to the Green's functions for our examples are derived.},
  subject      = {Physik},
  language  = {en}
}