@article{9897, author = {{Protte, Maximilian and Weber, Nils and Golla, Christian and Zentgraf, Thomas and Meier, Cedrik}}, issn = {{0021-8979}}, journal = {{Journal of Applied Physics}}, title = {{{Strong nonlinear optical response from ZnO by coupled and lattice-matched nanoantennas}}}, doi = {{10.1063/1.5093257}}, volume = {{125}}, year = {{2019}}, } @article{12930, author = {{Köthemann, Ronja and Weber, Nils and Lindner, Jörg K N and Meier, Cedrik}}, issn = {{0268-1242}}, journal = {{Semiconductor Science and Technology}}, number = {{9}}, title = {{{High-precision determination of silicon nanocrystals: optical spectroscopy versus electron microscopy}}}, doi = {{10.1088/1361-6641/ab3536}}, volume = {{34}}, year = {{2019}}, } @article{14544, author = {{Vondran, J. and Spitzer, F. and Bayer, M. and Akimov, I. A. and Trautmann, Alexander and Reichelt, Matthias and Meier, Cedrik and Weber, N. and Meier, Torsten and André, R. and Mariette, H.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{15}}, pages = {{155308}}, title = {{{Spatially asymmetric transients of propagating exciton-polariton modes in a planar CdZnTe/CdMgTe guiding structure}}}, doi = {{10.1103/physrevb.100.155308}}, volume = {{100}}, year = {{2019}}, } @article{10014, abstract = {{The cubic, tetragonal, and orthorhombic phase of potassium niobate (KNbO3) are studied based on density-functional theory. Starting from the relaxed atomic geometries, we analyze the influence of self-energy corrections on the electronic band structure within the GW approximation. We find that quasiparticle shifts widen the direct (indirect) band gap by 1.21 (1.44), 1.58 (1.55), and 1.67 (1.64) eV for the cubic, tetragonal, and orthorhombic phase, respectively. By solving the Bethe-Salpeter equation, we obtain the linear dielectric function with excitonic and local-field effects, which turn out to be essential for good agreement with experimental data. From our results, we extract an exciton binding energy of 0.6, 0.5, and 0.5 eV for the cubic, tetragonal, and orthorhombic phase, respectively. Furthermore, we investigate the nonlinear second-harmonic generation (SHG) both theoretically and experimentally. The frequency-dependent second-order polarization tensor of orthorhombic KNbO3 is measured for incoming photon energies between 1.2 and 1.6 eV. In addition, calculations within the independent-(quasi)particle approximation are performed for the tetragonal and orthorhombic phase. The novel experimental data are in excellent agreement with the quasiparticle calculations and resolve persistent discrepancies between earlier experimental measurements and ab initio results reported in the literature.}}, author = {{Schmidt, Falko and Riefer, Arthur and Schmidt, Wolf Gero and Schindlmayr, Arno and Imlau, Mirco and Dobener, Florian and Mengel, Nils and Chatterjee, Sangam and Sanna, Simone}}, issn = {{2475-9953}}, journal = {{Physical Review Materials}}, number = {{5}}, publisher = {{American Physical Society}}, title = {{{Quasiparticle and excitonic effects in the optical response of KNbO3}}}, doi = {{10.1103/PhysRevMaterials.3.054401}}, volume = {{3}}, year = {{2019}}, } @article{29746, author = {{Nicholson, C. W. and Puppin, M. and Lücke, A. and Gerstmann, Uwe and Krenz, Marvin and Schmidt, Wolf Gero and Rettig, L. and Ernstorfer, R. and Wolf, M.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{15}}, publisher = {{American Physical Society (APS)}}, title = {{{Excited-state band mapping and momentum-resolved ultrafast population dynamics in In/Si(111) nanowires investigated with XUV-based time- and angle-resolved photoemission spectroscopy}}}, doi = {{10.1103/physrevb.99.155107}}, volume = {{99}}, year = {{2019}}, } @article{10015, author = {{Dues, Christof and Schmidt, Wolf Gero and Sanna, Simone}}, issn = {{2470-1343}}, journal = {{ACS Omega}}, pages = {{3850--3859}}, title = {{{Water Splitting Reaction at Polar Lithium Niobate Surfaces}}}, doi = {{10.1021/acsomega.8b03271}}, year = {{2019}}, } @article{13365, abstract = {{The KTiOPO4 (KTP) band structure and dielectric function are calculated on various levels of theory starting from density-functional calculations. Within the independent-particle approximation an electronic transport gap of 2.97 eV is obtained that widens to about 5.23 eV when quasiparticle effects are included using the GW approximation. The optical response is shown to be strongly anisotropic due to (i) the slight asymmetry of the TiO6 octahedra in the (001) plane and (ii) their anisotropic distribution along the [001] and [100] directions. In addition, excitonic effects are very important: The solution of the Bethe–Salpeter equation indicates exciton binding energies of the order of 1.5 eV. Calculations that include both quasiparticle and excitonic effects are in good agreement with the measured reflectivity.}}, author = {{Neufeld, Sergej and Bocchini, Adriana and Gerstmann, Uwe and Schindlmayr, Arno and Schmidt, Wolf Gero}}, issn = {{2515-7639}}, journal = {{Journal of Physics: Materials}}, pages = {{045003}}, publisher = {{IOP Publishing}}, title = {{{Potassium titanyl phosphate (KTP) quasiparticle energies and optical response}}}, doi = {{10.1088/2515-7639/ab29ba}}, volume = {{2}}, year = {{2019}}, } @article{22887, author = {{Vondran, J. and Spitzer, F. and Bayer, M. and Akimov, I. A. and Trautmann, Alexander and Reichelt, Matthias and Meier, Cedrik and Weber, N. and Meier, Torsten and André, R. and Mariette, H.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{15}}, pages = {{155308}}, title = {{{Spatially asymmetric transients of propagating exciton-polariton modes in a planar CdZnTe/CdMgTe guiding structure}}}, doi = {{10.1103/physrevb.100.155308}}, volume = {{100}}, year = {{2019}}, } @article{13429, author = {{Bocchini, Adriana and Neufeld, Sergej and Gerstmann, Uwe and Schmidt, Wolf Gero}}, issn = {{0953-8984}}, journal = {{Journal of Physics: Condensed Matter}}, pages = {{385401}}, title = {{{Oxygen and potassium vacancies in KTP calculated from first principles}}}, doi = {{10.1088/1361-648x/ab295c}}, volume = {{31}}, year = {{2019}}, } @article{1430, author = {{Hoffmann, Sandro P. and Albert, Maximilian and Weber, Nils and Sievers, Denis and Förstner, Jens and Zentgraf, Thomas and Meier, Cedrik}}, issn = {{2330-4022}}, journal = {{ACS Photonics}}, keywords = {{tet_topic_phc}}, pages = {{1933--1942}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Tailored UV Emission by Nonlinear IR Excitation from ZnO Photonic Crystal Nanocavities}}}, doi = {{10.1021/acsphotonics.7b01228}}, volume = {{5}}, year = {{2018}}, } @article{10013, abstract = {{Ultrafast nonequilibrium dynamics offer a route to study the microscopic interactions that govern macroscopic behavior. In particular, photoinduced phase transitions (PIPTs) in solids provide a test case for how forces, and the resulting atomic motion along a reaction coordinate, originate from a nonequilibrium population of excited electronic states. Using femtosecond photoemission, we obtain access to the transient electronic structure during an ultrafast PIPT in a model system: indium nanowires on a silicon(111) surface. We uncover a detailed reaction pathway, allowing a direct comparison with the dynamics predicted by ab initio simulations. This further reveals the crucial role played by localized photoholes in shaping the potential energy landscape and enables a combined momentum- and real-space description of PIPTs, including the ultrafast formation of chemical bonds.}}, author = {{Nicholson, C. W. and Lücke, A. and Schmidt, Wolf Gero and Puppin, M. and Rettig, L. and Ernstorfer, R. and Wolf, M.}}, issn = {{0036-8075}}, journal = {{Science}}, pages = {{821--825}}, title = {{{Beyond the molecular movie: Dynamics of bands and bonds during a photoinduced phase transition}}}, doi = {{10.1126/science.aar4183}}, year = {{2018}}, } @article{10016, author = {{Paszkiewicz, Mateusz and Biktagirov, Timur and Aldahhak, Hazem and Allegretti, Francesco and Rauls, Eva and Schöfberger, Wolfgang and Schmidt, Wolf Gero and Barth, Johannes V. and Gerstmann, Uwe and Klappenberger, Florian}}, issn = {{1948-7185}}, journal = {{The Journal of Physical Chemistry Letters}}, pages = {{6412--6420}}, title = {{{Unraveling the Oxidation and Spin State of Mn–Corrole through X-ray Spectroscopy and Quantum Chemical Analysis}}}, doi = {{10.1021/acs.jpclett.8b02525}}, year = {{2018}}, } @article{10019, author = {{Aldahhak, Hazem and Paszkiewicz, M. and Rauls, E. and Allegretti, F. and Tebi, S. and Papageorgiou, A. C. and Zhang, Y.-Q. and Zhang, L. and Lin, T. and Paintner, T. and Koch, R. and Schmidt, Wolf Gero and Barth, J. V. and Schöfberger, W. and Müllegger, S. and Klappenberger, F. and Gerstmann, Uwe}}, issn = {{0947-6539}}, journal = {{Chemistry - A European Journal}}, pages = {{6787--6797}}, title = {{{Identifying On-Surface Site-Selective Chemical Conversions by Theory-Aided NEXAFS Spectroscopy: The Case of Free-Base Corroles on Ag(111)}}}, doi = {{10.1002/chem.201705921}}, year = {{2018}}, } @article{4769, abstract = {{In recent years, Raman spectroscopy has been used to visualize and analyze ferroelectric domain structures. The technique makes use of the fact that the intensity or frequency of certain phonons is strongly influenced by the presence of domain walls. Although the method is used frequently, the underlying mechanism responsible for the changes in the spectra is not fully understood. This inhibits deeper analysis of domain structures based on this method. Two different models have been proposed. However, neither model completely explains all observations. In this work, we have systematically investigated domain walls in different scattering geometries with Raman spectroscopy in the common ferroelectric materials used in integrated optics, i.e., KTiOPO4, LiNbO3, and LiTaO3. Based on the two models, we can demonstrate that the observed contrast for domain walls is in fact based on two different effects. We can identify on the one hand microscopic changes at the domain wall, e.g., strain and electric fields, and on the other hand a macroscopic change of selection rules at the domain wall. While the macroscopic relaxation of selection rules can be explained by the directional dispersion of the phonons in agreement with previous propositions, the microscopic changes can be explained qualitatively in terms of a simplified atomistic model.}}, author = {{Rüsing, Michael and Neufeld, Sergej and Brockmeier, Julian and Eigner, Christof and Mackwitz, P. and Spychala, K. and Silberhorn, Christine and Schmidt, Wolf Gero and Berth, Gerhard and Zrenner, Artur and Sanna, S.}}, issn = {{2475-9953}}, journal = {{Physical Review Materials}}, number = {{10}}, publisher = {{American Physical Society (APS)}}, title = {{{Imaging of 180∘ ferroelectric domain walls in uniaxial ferroelectrics by confocal Raman spectroscopy: Unraveling the contrast mechanism}}}, doi = {{10.1103/physrevmaterials.2.103801}}, volume = {{2}}, year = {{2018}}, } @article{4370, author = {{Schmidt, C. and Bühler, J. and Heinrich, A.-C. and Allerbeck, J. and Podzimski, R. and Berghoff, D. and Meier, Torsten and Schmidt, Wolf Gero and Reichl, C. and Wegscheider, W. and Brida, D. and Leitenstorfer, A.}}, issn = {{2041-1723}}, journal = {{Nature Communications}}, number = {{1}}, publisher = {{Springer Nature}}, title = {{{Signatures of transient Wannier-Stark localization in bulk gallium arsenide}}}, doi = {{10.1038/s41467-018-05229-x}}, volume = {{9}}, year = {{2018}}, } @article{10018, author = {{Schmidt, Claudia and Bühler, J. and Heinrich, A.-C. and Allerbeck, J. and Podzimski, R. and Berghoff, Daniel and Meier, Torsten and Schmidt, Wolf Gero and Reichl, C. and Wegscheider, W. and Brida, D. and Leitenstorfer, A.}}, issn = {{2041-1723}}, journal = {{Nature Communications}}, title = {{{Signatures of transient Wannier-Stark localization in bulk gallium arsenide}}}, doi = {{10.1038/s41467-018-05229-x}}, volume = {{9}}, year = {{2018}}, } @article{13410, author = {{Friedrich, Michael and Schmidt, Wolf Gero and Schindlmayr, Arno and Sanna, Simone}}, issn = {{2475-9953}}, journal = {{Physical Review Materials}}, number = {{1}}, publisher = {{American Physical Society}}, title = {{{Erratum: Optical properties of titanium-doped lithium niobate from time-dependent density-functional theory [Phys. Rev. Materials 1, 034401 (2017)]}}}, doi = {{10.1103/PhysRevMaterials.2.019902}}, volume = {{2}}, year = {{2018}}, } @article{17065, author = {{Esser, Norbert and Schmidt, Wolf Gero}}, issn = {{0370-1972}}, journal = {{physica status solidi (b)}}, number = {{256}}, title = {{{Electric Field Induced Raman Scattering at the Sb–InP(110) Interface: The Surface Dipole Contribution}}}, doi = {{10.1002/pssb.201800314}}, year = {{2018}}, } @article{10020, author = {{Landmann, M. and Rauls, E. and Schmidt, Wolf Gero}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, title = {{{Understanding band alignments in semiconductor heterostructures: Composition dependence and type-I–type-II transition of natural band offsets in nonpolar zinc-blendeAlxGa1−xN/AlyGa1−yNcomposites}}}, doi = {{10.1103/physrevb.95.155310}}, year = {{2017}}, } @article{3434, abstract = {{In this work we study the impact of ion implantation on the nonlinear optical properties in MgO:LiNbO3 via confocal second-harmonic microscopy. In detail, we spatially characterize the nonlinear susceptibility in carbon-ion implanted lithium niobate planar waveguides for different implantation energies and fluences, as well as the effect of annealing. In a further step, a computational simulation is used to calculate the implantation range of carbon-ions and the corresponding defect density distribution. A comparison between the simulation and the experimental data indicates that the depth profile of the second-order effective nonlinear coefficient is directly connected to the defect density that is induced by the ion irradiation. Furthermore it can be demonstrated that the annealing treatment partially recovers the second-order optical susceptibility.}}, author = {{Spychala, Kai J. and Berth, Gerhard and Widhalm, Alex and Rüsing, Michael and Wang, Lei and Sanna, Simone and Zrenner, Artur}}, issn = {{1094-4087}}, journal = {{OPTICS EXPRESS}}, number = {{18}}, pages = {{21444----21453}}, title = {{{Impact of carbon-ion implantation on the nonlinear optical susceptibility of LiNbO3}}}, doi = {{10.1364/OE.25.021444}}, year = {{2017}}, }