TY - CHAP A1 - Rechenauer, Christian A1 - Neuleitner, Nikolaus A1 - Steffens, Oliver T1 - Empirische Untersuchung und Optimierung der Performance eines Modellprojekts für ein Effizienzhaus Plus mit solarthermischem Energiekonzept T2 - Fachforum Effizienzhaus Plus, 14.07.2015 Y1 - 2015 CY - Hamburg ER - TY - RPRT A1 - Steffens, Oliver T1 - Saisonale Wärmespeicherung von opaken Bauteilen im Massivbau BT - Literatur-Übersicht Y1 - 2015 ER - TY - JOUR A1 - Raith, Lea A1 - Schmidling, Anja A1 - Windisch, Bastian T1 - Bauteiltemperierung BT - Studienarbeit Y1 - 2012 CY - Regensburg ER - TY - JOUR A1 - Steffens, Oliver A1 - Suhrke, Michael A1 - Rotter, Peter A1 - Rössler, Ulrich T1 - From Landau levels to universal fluctuations: Level statistics for lateral superlattices JF - Physical Review B N2 - We study the energy-level statistics for electrons in a lateral two-dimensional superlattice in dependence on the strength of the modulation potential at a given perpendicular magnetic field. The interminiband statistics at some selected point in the magnetic Brillouin zone shows a transition from degenerate Landau levels to universal spectral correlations while the corresponding classical dynamics displays a crossover from regular cyclotron orbits to chaotic motion. In terms of the nearest-neighbor spacing distribution, we observe the occurrence of level repulsion for all nonzero modulation amplitudes, which indicates a discontinuous transition to universal fluctuations for the smallest level spacings when the rotational invariance of the system is broken by a finite superlattice potential. In order to test the universality of the transition on larger scales, we propose a random matrix model with one transition parameter for comparison. Confirmed by two different types of potential shapes, we detect an explicit influence of the potential shape on the level spacing distributions, which hence cannot be described by the one-parameter model. Using the spectral rigidity, however, universal long-range fluctuations in the regime of negligible Landau-level mixing are found, in agreement with our random matrix model. Y1 - 1997 U6 - https://doi.org/10.1103/PhysRevB.55.4486 VL - 55 IS - 7 SP - 4486 EP - 4493 ER - TY - JOUR A1 - Steffens, Oliver A1 - Wensauer, Andreas A1 - Suhrke, Michael T1 - Collective excitations in quantum dots: Calculated Raman spectra JF - physica status solidi (b) N2 - Electronic Raman scattering provides information on excited states, whose collective character as being related to the charge or spin density can be distinguished by using different polarization configurations. We employ time-dependent spin-density functional theory to calculate Raman spectra for circular semiconductor quantum dots with up to 10 electrons for the polarized and depolarized configuration and in dependence on an external magnetic field and the momentum transfer. Our results demonstrate an increase of the collective (or many-particle) character of the excitations with increasing momentum transfer and a mixing of spin- and charge-density modes for excitations from ground states with finite spin density. These results have predictive character, because corresponding experiments on few-electron dots have not yet been performed. Y1 - 1999 U6 - https://doi.org/10.1002/(SICI)1521-3951(199909)215:1<365::AID-PSSB365>3.0.CO;2-C VL - 215 SP - 365 EP - 371 PB - Wiley ER - TY - JOUR A1 - Suhrke, Michael A1 - Steffens, Oliver A1 - Rotter, Peter A1 - Rössler, Ulrich T1 - Quantum chaos and magnetotransport in lateral superlattices: The transition from weak to strong modulation potential JF - Physica E: Low-dimensional Systems and Nanostructures N2 - Magnetotransport in lateral superlattices covers a variety of apparently different physics dependent on the amplitude of the modulation potential relative to the Fermi energy ranging from the weakly modulated 2DEG to the antidot lattice. Here we investigate the transition between weak modulation and antidots within the quantum-mechanical theory by studying (i) the single-particle spectrum with respect to quantum signatures of classical chaos and (ii) the change of characteristic features in the magnetoresistance starting from the Kubo formula. KW - Lateral superlattices KW - Quantum chaos KW - Level statistics KW - Magnetotransport KW - Commensurability oscillations Y1 - 1997 U6 - https://doi.org/10.1016/S1386-9477(97)00060-X SN - 1386-9477 VL - 1 IS - 1-4 SP - 281 EP - 287 ER - TY - RPRT A1 - Steffens, Oliver A1 - Rössler, Ulrich A1 - Suhrke, Michael T1 - Comment on "Shell Filling and Spin Effects in a Few Electron Quantum Dot" T2 - Physical Review Letters N2 - We briefly report on calculated addition spectra for electrons in a circular quantum dot with perpendicular magnetic field. We compare our current density functional theory calculations with recent experiments by Tarucha et al. [PRL 77, 3613 (1996)]. We find a very good qualitative agreement of the structures and find an additional effect caused by Hund's first rule in magnetic field, which gives rise to new substructures not discussed in the paper by Tarucha. Y1 - 1996 UR - http://arxiv.org/abs/cond-mat/9711077 VL - 77 SP - 3613 ER - TY - JOUR A1 - Steffens, Oliver T1 - Energetische Modernisierung und Restaurierung historisch wertvoller Stadtquartiere. Regenerative Energieversorgung als Schwerpunkt einer nachhaltigen Modernisierung historisch wertvoller Stadtquartiere (RENARHIS) JF - Zukunft bauen. Forschungsinitiative Zukunft Bau 2016 Y1 - 2016 IS - 5 SP - 62 EP - 65 PB - Bundesministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit (BMUB) ER - TY - GEN A1 - Steffens, Oliver A1 - Saller, Tobias T1 - Modernisierungskonzepte für das denkmalgeschützte Ensemble am Jahn-Stadion Regensburg Prüfeninger Straße 47–52 BT - Studiengang Gebäudeklimatik. Studienarbeiten Y1 - 2014 ER - TY - CHAP A1 - Höller, Christoph A1 - Steffens, Oliver T1 - Bauphysikalische Grundlagenausbildung an der OTH Regensburg während der COVID-19-Pandemie T2 - Tagungsband DAGA 2021: 47. Jahrestagung für Akustik, 15.-18. August 2021, Wien und Online Y1 - 2021 UR - https://www.dega-akustik.de/publikationen/online-proceedings SN - 978-3-939296-18-8 PB - Deutsche Gesellschaft für Akustik e.V. ER -