@article{13820, author = {{Schmidt, Wolf Gero and Wippermann, S. and Sanna, S. and Babilon, M. and Vollmers, N. J. and Gerstmann, Uwe}}, issn = {{0370-1972}}, journal = {{physica status solidi (b)}}, number = {{2}}, pages = {{343--359}}, title = {{{In-Si(111)(4 × 1)/(8 × 2) nanowires: Electron transport, entropy, and metal-insulator transition}}}, doi = {{10.1002/pssb.201100457}}, volume = {{249}}, year = {{2012}}, } @article{15872, author = {{Montgomery, Neil A. and Hedley, Gordon J. and Ruseckas, Arvydas and Denis, Jean-Christophe and Schumacher, Stefan and Kanibolotsky, Alexander L. and Skabara, Peter J. and Galbraith, Ian and Turnbull, Graham A. and Samuel, Ifor D. W.}}, issn = {{1463-9076}}, journal = {{Physical Chemistry Chemical Physics}}, title = {{{Dynamics of fluorescence depolarisation in star-shaped oligofluorene-truxene molecules}}}, doi = {{10.1039/c2cp24141b}}, year = {{2012}}, } @article{18542, abstract = {{We present recent advances in numerical implementations of hybrid functionals and the GW approximation within the full-potential linearized augmented-plane-wave (FLAPW) method. The former is an approximation for the exchange–correlation contribution to the total energy functional in density-functional theory, and the latter is an approximation for the electronic self-energy in the framework of many-body perturbation theory. All implementations employ the mixed product basis, which has evolved into a versatile basis for the products of wave functions, describing the incoming and outgoing states of an electron that is scattered by interacting with another electron. It can thus be used for representing the nonlocal potential in hybrid functionals as well as the screened interaction and related quantities in GW calculations. In particular, the six-dimensional space integrals of the Hamiltonian exchange matrix elements (and exchange self-energy) decompose into sums over vector–matrix–vector products, which can be evaluated easily. The correlation part of the GW self-energy, which contains a time or frequency dependence, is calculated on the imaginary frequency axis with a subsequent analytic continuation to the real axis or, alternatively, by a direct frequency convolution of the Green function G and the dynamically screened Coulomb interaction W along a contour integration path that avoids the poles of the Green function. Hybrid-functional and GW calculations are notoriously computationally expensive. We present a number of tricks that reduce the computational cost considerably, including the use of spatial and time-reversal symmetries, modifications of the mixed product basis with the aim to optimize it for the correlation self-energy and another modification that makes the Coulomb matrix sparse, analytic expansions of the interaction potentials around the point of divergence at k=0, and a nested density and density-matrix convergence scheme for hybrid-functional calculations. We show CPU timings for prototype semiconductors and illustrative results for GdN and ZnO. }}, author = {{Friedrich, Christoph and Betzinger, Markus and Schlipf, Martin and Blügel, Stefan and Schindlmayr, Arno}}, issn = {{1361-648X}}, journal = {{Journal of Physics: Condensed Matter}}, number = {{29}}, publisher = {{IOP Publishing}}, title = {{{Hybrid functionals and GW approximation in the FLAPW method}}}, doi = {{10.1088/0953-8984/24/29/293201}}, volume = {{24}}, year = {{2012}}, } @article{3974, abstract = {{We study the quantum properties and statistics of photons emitted by a quantum-dot biexciton inside a cavity. In the biexciton-exciton cascade, fine-structure splitting between exciton levels degrades polarization-entanglement for the emitted pair of photons. However, here we show that the polarization-entanglement can be preserved in such a system through simultaneous emission of two degenerate photons into cavity modes tuned to half the biexciton energy. Based on detailed theoretical calculations for realistic quantum-dot and cavity parameters, we quantify the degree of achievable entanglement.}}, author = {{Schumacher, Stefan and Förstner, Jens and Zrenner, Artur and Florian, Matthias and Gies, Christopher and Gartner, Paul and Jahnke, Frank}}, issn = {{1094-4087}}, journal = {{Optics Express}}, keywords = {{tet_topic_qd}}, number = {{5}}, pages = {{5335--5342}}, publisher = {{OSA}}, title = {{{Cavity-assisted emission of polarization-entangled photons from biexcitons in quantum dots with fine-structure splitting}}}, doi = {{10.1364/oe.20.005335}}, volume = {{20}}, year = {{2012}}, } @article{40405, author = {{Sharapova, Polina and Tikhonova, O V}}, issn = {{1063-7818}}, journal = {{Quantum Electronics}}, keywords = {{Electrical and Electronic Engineering, Atomic and Molecular Physics, and Optics, Statistical and Nonlinear Physics, Electronic, Optical and Magnetic Materials}}, number = {{3}}, pages = {{199--207}}, publisher = {{IOP Publishing}}, title = {{{Dynamics of ionisation and entanglement in the 'atom + quantum electromagnetic field' system}}}, doi = {{10.1070/qe2012v042n03abeh014805}}, volume = {{42}}, year = {{2012}}, } @inproceedings{3965, abstract = {{We design the geometrical shape of plasmonic nanostructures to achieve field patterns with desired properties. For this, we combine Maxwell simulations and automatic optimization techniques. By allowing variations of the geometrical shape, which can be based on either boxes or arbitrary polygons, we maximize the desired objective.}}, author = {{Hildebrandt, Andre and Reichelt, Matthias and Meier, Torsten and Förstner, Jens}}, keywords = {{tet_topic_optical antenna, tet_topic_plasmonics}}, location = {{Bad Honnef}}, number = {{59}}, publisher = {{AIP AIP Conference Proceedings 1475}}, title = {{{Optimization of the intensity enhancement in plasmonic nanoantennas}}}, doi = {{10.1063/1.4750095}}, year = {{2012}}, } @article{4136, abstract = {{Results of atomistic simulations aimed at understanding precipitation of the highly attractive wide band gap semiconductor material silicon carbide in silicon are presented. The study involves a systematic investigation of intrinsic and carbon-related defects as well as defect combinations and defect migration by both, quantummechanical first-principles as well as empirical potential methods. Comparing formation and activation energies, ground-state structures of defects and defect combinations as well as energetically favorable agglomeration of defects are predicted. Moreover, accurate ab initio calculations unveil limitations of the analytical method based on a Tersoff-like bond order potential. A work-around is proposed in order to subsequently apply the highly efficient technique on large structures not accessible by first-principles methods. The outcome of both types of simulation provides a basic microscopic understanding of defect formation and structural evolution particularly at non-equilibrium conditions strongly deviated from the ground state as commonly found in SiC growth processes. A possible precipitation mechanism, which conforms well to experimental findings and clarifies contradictory views present in the literature is outlined.}}, author = {{Zirkelbach, F. and Stritzker, B. and Nordlund, K. and Schmidt, Wolf Gero and Rauls, E. and Lindner, Jörg K. N.}}, issn = {{1862-6351}}, journal = {{physica status solidi (c)}}, number = {{10-11}}, pages = {{1968--1973}}, publisher = {{Wiley}}, title = {{{First-principles and empirical potential simulation study of intrinsic and carbon-related defects in silicon}}}, doi = {{10.1002/pssc.201200198}}, volume = {{9}}, year = {{2012}}, } @article{3972, abstract = {{Using a finite-difference time-domain method, we theoretically investigate the optical spectra of crossing perpendicular photonic crystal waveguides with quantum dots embedded in the central rod. The waveguides are designed so that the light mainly propagates along one direction and the cross talk is greatly reduced in the transverse direction. It is shown that when a quantum dot (QD) is resonant with the cavity, strong coupling can be observed via both the transmission and crosstalk spectrum. If the cavity is far off-resonant from the QD, both the cavity mode and the QD signal can be detected in the transverse direction since the laser field is greatly suppressed in this direction. This structure could have strong implications for resonant excitation and in-plane detection of QD optical spectroscopy.}}, author = {{Song, Xiaohong and Declair, Stefan and Meier, Torsten and Zrenner, Artur and Förstner, Jens}}, issn = {{1094-4087}}, journal = {{Optics Express}}, keywords = {{tet_topic_phc, tet_topic_qd}}, number = {{13}}, pages = {{14130--14136}}, publisher = {{The Optical Society}}, title = {{{Photonic crystal waveguides intersection for resonant quantum dot optical spectroscopy detection}}}, doi = {{10.1364/oe.20.014130}}, volume = {{20}}, year = {{2012}}, } @inproceedings{3967, abstract = {{We simulate the linear and nonlinear optical response from split-ring resonator (SRR) arrays to study collective effects between the constituent SRRs that determine spectral properties of the second harmonic generation (SHG). We apply the Discontinuous Galerkin Time Domain (DGTD) method and the hydrodynamic Maxwell-Vlasov model to calculate the SHG emission. Our model is able to qualitatively reproduce and explain the non-monotonic dependence of the spectral SHG transmission measured experimentally for SRR arrays with different lattice constants}}, author = {{Grynko, Yevgen and Meier, Torsten and Linden, Stefan and Niesler, Fabian B. P. and Wegener, Martin and Förstner, Jens}}, keywords = {{tet_topic_meta, tet_topic_shg}}, location = {{Bad Honnef}}, number = {{1}}, pages = {{128--130}}, publisher = {{AIP Conference Proceedings}}, title = {{{Near-field coupling and second-harmonic generation in split-ring resonator arrays}}}, doi = {{10.1063/1.4750118}}, volume = {{1475}}, year = {{2012}}, } @article{3970, abstract = {{Optical experiments on second-harmonic generation from split-ring-resonator square arrays show a nonmonotonic dependence of the conversion efficiency on the lattice constant. This finding is interpreted in terms of a competition between dilution effects and linewidth or near-field changes due to interactions among the individual elements in the array.}}, author = {{Linden, S. and Niesler, F. B. P. and Förstner, Jens and Grynko, Yevgen and Meier, Torsten and Wegener, M.}}, issn = {{0031-9007}}, journal = {{Physical Review Letters}}, keywords = {{tet_topic_shg, tet_topic_meta}}, number = {{1}}, publisher = {{American Physical Society (APS)}}, title = {{{Collective Effects in Second-Harmonic Generation from Split-Ring-Resonator Arrays}}}, doi = {{10.1103/physrevlett.109.015502}}, volume = {{109}}, year = {{2012}}, } @article{43200, abstract = {{A novel adaptive approach to compute the eigenenergies and eigenfunctions of the two-particle (electron-hole) Schrödinger equation including Coulomb attraction is presented. As an example, we analyze the energetically lowest exciton state of a thin one-dimensional semiconductor quantum wire in the presence of disorder which arises from the non-smooth interface between the wire and surrounding material. The eigenvalues of the corresponding Schrödinger equation, i.e., the one-dimensional exciton Wannier equation with disorder, correspond to the energies of excitons in the quantum wire. The wavefunctions, in turn, provide information on the optical properties of the wire. We reformulate the problem of two interacting particles that both can move in one dimension as a stationary eigenvalue problem with two spacial dimensions in an appropriate weak form whose bilinear form is arranged to be symmetric, continuous, and coercive. The disorder of the wire is modelled by adding a potential in the Hamiltonian which is generated by normally distributed random numbers. The numerical solution of this problem is based on adaptive wavelets. Our scheme allows for a convergence proof of the resulting scheme together with complexity estimates. Numerical examples demonstrate the behavior of the smallest eigenvalue, the ground state energies of the exciton, together with the eigenstates depending on the strength and spatial correlation of disorder.}}, author = {{Meier, Torsten and Mollet, Christian and Kunoth, Angela}}, journal = {{Communications in Computational Physics}}, number = {{1}}, pages = {{21--47}}, publisher = {{Cambridge University Press}}, title = {{{Excitonic Eigenstates of Disordered Semiconductor Quantum Wires: Adaptive Wavelet Computation of Eigenvalues for the Electron-Hole Schrödinger Equation}}}, doi = {{10.4208/cicp.081011.260712a}}, volume = {{14}}, year = {{2012}}, } @inproceedings{4312, abstract = {{The intensity dependence of optically-induced injection currents in semiconductor quantum wells is investigated numerically. Oscillatory behavior of the electron charge current transients as function of intensity and time is predicted and explained.}}, author = {{Pochwala, Michal and Duc, Huynh Thanh and Förstner, Jens and Meier, Torsten}}, booktitle = {{CLEO:2011 - Laser Applications to Photonic Applications}}, isbn = {{9781557529107}}, issn = {{2160-8989 }}, keywords = {{tet_topic_qw}}, location = {{Baltimore, Maryland (USA)}}, publisher = {{Optical Society of America}}, title = {{{Intensity dependence of optically-induced injection currents in semiconductor quantum wells}}}, doi = {{10.1364/qels.2011.qmk4}}, year = {{2011}}, } @inproceedings{4043, abstract = {{We present numerical results of the mutual coupling between photonic crystal cavities and semiconductor quantum dots. Normal mode splitting between a single cavity mode and a single quantum dot is shown under weak excitation, while under strong excitation Q‐factor dependent side bands appear, according to the AC‐Stark effect. Coupled photonic crystals, aligned parallel but displaced under a 30°‐angle for efficient coupling, show line splittings of all eigenmodes, if a single eigenmode is resonantly coupled to a single quantum dot. The mutual coupling of N resonant quantum dots to a single cavity mode results in a N−−√ scaling of the splitting, known from quantum optics, but corrected by the field amplitude fraction for not collocated quantum dots.}}, author = {{Declair, S. and Song, X. and Meier, Torsten and Förstner, Jens}}, booktitle = {{THE FOURTH INTERNATIONAL WORKSHOP 2011}}, keywords = {{tet_topic_phc, tet_topic_qd}}, location = {{Bad Honnef}}, number = {{123}}, pages = {{123--125}}, publisher = {{AIP}}, title = {{{Simulation of Mutual Coupling of Photonic Crystal Cavity Modes and Semiconductor Quantum Dots}}}, doi = {{10.1063/1.3644232}}, volume = {{1398}}, year = {{2011}}, } @article{44059, abstract = {{A novel adaptive wavelet based method is presented that allows us to compute eigenvalues and eigenvectors of the electronic Schrödinger equation. Our method outperforms direct discretization methods with equidistant grid spacings, in particular, for problems that involve several length scales. As an application we present numerical evaluations of the energetically lowest exciton states for ordered and disordered semiconductor quantum wires.}}, author = {{Meier, Torsten and Mollet, Christian and Kunoth, Angela}}, journal = {{AIP Conference Proceedings}}, number = {{1}}, pages = {{156--158}}, publisher = {{American Institute of Physics}}, title = {{{Wavelet‐Based Adaptive Computations of the Excitonic Eigenstates of Disordered Semiconductor Quantum Wires}}}, doi = {{10.1063/1.3644243}}, volume = {{1398}}, year = {{2011}}, } @inproceedings{4048, abstract = {{We present an ab-initio method for calculating nonlinear and nonlocal optical effects in metallic slabs with sub-wavelength thickness. We find a strong localization of the second-harmonic current at the metal-vacuum interface.}}, author = {{Wand, Mathias and Schindlmayr, Arno and Meier, Torsten and Förstner, Jens}}, booktitle = {{CLEO:2011 - Laser Applications to Photonic Applications }}, isbn = {{978-1-4577-1223-4}}, issn = {{2160-8989}}, keywords = {{tet_topic_shg}}, location = {{Baltimore, Maryland, United States}}, publisher = {{Optical Society of America}}, title = {{{Theoretical approach to the ultrafast nonlinear optical response of metal slabs}}}, doi = {{10.1364/CLEO_AT.2011.JTuI59}}, year = {{2011}}, } @article{43259, abstract = {{The extreme nonlinear terahertz response of initially unexcited intrinsic semiconductor nanostructures is studied theoretically by solving extended semiconductor Bloch equations numerically. The coupled dynamics of intraband acceleration and multiphoton interband transitions leads to high-harmonic generation up to several tens of the exciting terahertz frequency. It is shown that the actual cut-off frequency is determined by the band structure and not by the excitation strength.}}, author = {{Golde, D. and Kira, M. and Meier, Torsten and Koch, S.W.}}, journal = {{physica status solidi (b)}}, number = {{4}}, pages = {{863--866}}, publisher = {{WILEY‐VCH Verlag}}, title = {{{Microscopic theory of the extremely nonlinear terahertz response of semiconductors}}}, doi = {{10.1002/pssb.201000840}}, volume = {{248}}, year = {{2011}}, } @inproceedings{44060, abstract = {{In recent years, single-walled carbon nanotubes (SWCNTs) have received widespread attention due to their perfect quasi-one-dimensional structure and unique physical properties, as well as their potential for applications. In the present work, we calculate the band structure of SWCNTs using an atomistic tight-binding model including spin-orbit interaction. We combine this approach with a many-particle calculation of the nonlinear optical response using multi-band semiconductor Bloch equations. We show that, for SWCNTs lacking inversion symmetry, the intrinsic spin-orbit interaction can give rise to single-color photoinduced charge and spin currents. In particular, we study the influence of excitonic effects on these photoinduced currents and draw the analogy to recent investigations on single-color injection of photocurrents in semiconductor quantum wells.}}, author = {{Meier, Torsten and Liu, Hong and Duc, Huynh Thanh and Schumache, Stefan}}, booktitle = {{75. Annual meeting of the DPG and combined DPG Spring meeting}}, issn = {{0420-0195}}, location = {{Dresden, Germany}}, number = {{1}}, title = {{{Photocurrents in semiconductor carbon nanotubes with spin-orbit interaction}}}, volume = {{46}}, year = {{2011}}, } @inproceedings{44062, abstract = {{Optical two-dimensional Fourier transform spectroscopy has been used to study the properties of semiconductor nanostructures in four-wave-mixing like experiments. Applying a phenomenological level model, we numerically and analytically analyze the main features of excitonic and biexcitonic contributions in a semiconductor quantum well by solving the optical Bloch equations. The method is extended to three-dimensional Fourier transform spectroscopy to investigate a recent experiment.}}, author = {{Meier, Torsten and Wiebeler, Christian and Reichelt, Matthias}}, booktitle = {{ 75. Annual meeting of the DPG and combined DPG Spring meeting }}, issn = {{0420-0195}}, location = {{Dresden, Germany}}, number = {{1}}, title = {{{Analysis of multidimensional Fourier transform spectroscopy for semiconductors with a phenomenological level model}}}, volume = {{46}}, year = {{2011}}, } @inproceedings{44061, abstract = {{If a two-level system is excited with an intense light field of several times the Rabi frequency, the well-known Mollow triplets appear in the emitted radiation spectrum. We show that the pattern of the emission spectrum can be changed by using appropriately shaped laser pulses. The effect is also observable for a more realistic description of a semiconductor system.}}, author = {{Meier, Torsten and Reichelt, Matthias and Walther, Andrea}}, booktitle = {{75. Annual meeting of the DPG and combined DPG Spring meeting}}, issn = {{0420-0195}}, location = {{ Dresden, Germany}}, number = {{1}}, title = {{{Extreme nonlinear optics in semiconductors with shaped laser pulses}}}, volume = {{46}}, year = {{2011}}, } @inproceedings{4042, abstract = {{A simulation environment for metallic nanostructures based on the Discontinuous Galerkin Time Domain method is presented. It is used to model optical transmission by silver bi‐chiral plasmonic crystals. The results of simulations qualitatively and quantitavely agree with experimental measurements of transmitted circular polarization.}}, author = {{Grynko, Yevgen and Förstner, Jens and Meier, Torsten and Radke, André and Gissibl, Timo and Braun, Paul V. and Giessen, Harald}}, editor = {{Chigrin, Dmitry N.}}, keywords = {{tet_topic_meta}}, number = {{1}}, pages = {{76--78}}, publisher = {{AIP}}, title = {{{Application of the Discontinuous Galerkin Time Domain Method to the Optics of Bi-Chiral Plasmonic Crystals}}}, doi = {{10.1063/1.3644217}}, volume = {{1398}}, year = {{2011}}, }