@inproceedings{RechenauerNeuleitnerSteffens, author = {Rechenauer, Christian and Neuleitner, Nikolaus and Steffens, Oliver}, title = {Empirische Untersuchung und Optimierung der Performance eines Modellprojekts f{\"u}r ein Effizienzhaus Plus mit solarthermischem Energiekonzept}, series = {Fachforum Effizienzhaus Plus, 14.07.2015}, booktitle = {Fachforum Effizienzhaus Plus, 14.07.2015}, address = {Hamburg}, language = {de} } @techreport{Steffens, author = {Steffens, Oliver}, title = {Saisonale W{\"a}rmespeicherung von opaken Bauteilen im Massivbau}, language = {de} } @article{RaithSchmidlingWindisch, author = {Raith, Lea and Schmidling, Anja and Windisch, Bastian}, title = {Bauteiltemperierung}, address = {Regensburg}, language = {de} } @article{SteffensSuhrkeRotteretal., author = {Steffens, Oliver and Suhrke, Michael and Rotter, Peter and R{\"o}ssler, Ulrich}, title = {From Landau levels to universal fluctuations: Level statistics for lateral superlattices}, series = {Physical Review B}, volume = {55}, journal = {Physical Review B}, number = {7}, doi = {10.1103/PhysRevB.55.4486}, pages = {4486 -- 4493}, abstract = {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.}, language = {en} } @article{SteffensWensauerSuhrke, author = {Steffens, Oliver and Wensauer, Andreas and Suhrke, Michael}, title = {Collective excitations in quantum dots: Calculated Raman spectra}, series = {physica status solidi (b)}, volume = {215}, journal = {physica status solidi (b)}, publisher = {Wiley}, doi = {10.1002/(SICI)1521-3951(199909)215:1<365::AID-PSSB365>3.0.CO;2-C}, pages = {365 -- 371}, abstract = {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.}, language = {en} } @article{SuhrkeSteffensRotteretal., author = {Suhrke, Michael and Steffens, Oliver and Rotter, Peter and R{\"o}ssler, Ulrich}, title = {Quantum chaos and magnetotransport in lateral superlattices: The transition from weak to strong modulation potential}, series = {Physica E: Low-dimensional Systems and Nanostructures}, volume = {1}, journal = {Physica E: Low-dimensional Systems and Nanostructures}, number = {1-4}, issn = {1386-9477}, doi = {10.1016/S1386-9477(97)00060-X}, pages = {281 -- 287}, abstract = {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.}, language = {en} } @techreport{SteffensRoesslerSuhrke, author = {Steffens, Oliver and R{\"o}ssler, Ulrich and Suhrke, Michael}, title = {Comment on "Shell Filling and Spin Effects in a Few Electron Quantum Dot"}, series = {Physical Review Letters}, volume = {77}, journal = {Physical Review Letters}, pages = {3613}, abstract = {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.}, language = {en} } @article{Steffens, author = {Steffens, Oliver}, title = {Energetische Modernisierung und Restaurierung historisch wertvoller Stadtquartiere. Regenerative Energieversorgung als Schwerpunkt einer nachhaltigen Modernisierung historisch wertvoller Stadtquartiere (RENARHIS)}, series = {Zukunft bauen. Forschungsinitiative Zukunft Bau 2016}, journal = {Zukunft bauen. Forschungsinitiative Zukunft Bau 2016}, number = {5}, publisher = {Bundesministerium f{\"u}r Umwelt, Naturschutz, Bau und Reaktorsicherheit (BMUB)}, pages = {62 -- 65}, language = {de} } @misc{SteffensSaller, author = {Steffens, Oliver and Saller, Tobias}, title = {Modernisierungskonzepte f{\"u}r das denkmalgesch{\"u}tzte Ensemble am Jahn-Stadion Regensburg Pr{\"u}feninger Straße 47-52}, language = {de} } @inproceedings{HoellerSteffens, author = {H{\"o}ller, Christoph and Steffens, Oliver}, title = {Bauphysikalische Grundlagenausbildung an der OTH Regensburg w{\"a}hrend der COVID-19-Pandemie}, series = {Tagungsband DAGA 2021: 47. Jahrestagung f{\"u}r Akustik, 15.-18. August 2021, Wien und Online}, booktitle = {Tagungsband DAGA 2021: 47. Jahrestagung f{\"u}r Akustik, 15.-18. August 2021, Wien und Online}, publisher = {Deutsche Gesellschaft f{\"u}r Akustik e.V.}, isbn = {978-3-939296-18-8}, language = {de} }