@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{10023, abstract = {{We perform a comprehensive theoretical study of the structural and electronic properties of potassium niobate (KNbO3) in the cubic, tetragonal, orthorhombic, monoclinic, and rhombohedral phase, based on density-functional theory. The influence of different parametrizations of the exchange-correlation functional on the investigated properties is analyzed in detail, and the results are compared to available experimental data. We argue that the PBEsol and AM05 generalized gradient approximations as well as the RTPSS meta-generalized gradient approximation yield consistently accurate structural data for both the external and internal degrees of freedom and are overall superior to the local-density approximation or other conventional generalized gradient approximations for the structural characterization of KNbO3. Band-structure calculations using a HSE-type hybrid functional further indicate significant near degeneracies of band-edge states in all phases which are expected to be relevant for the optical response of the material.}}, author = {{Schmidt, Falko and Landmann, Marc and Rauls, Eva and Argiolas, Nicola and Sanna, Simone and Schmidt, Wolf Gero and Schindlmayr, Arno}}, issn = {{1687-8442}}, journal = {{Advances in Materials Science and Engineering}}, publisher = {{Hindawi}}, title = {{{Consistent atomic geometries and electronic structure of five phases of potassium niobate from density-functional theory}}}, doi = {{10.1155/2017/3981317}}, volume = {{2017}}, year = {{2017}}, } @article{10021, abstract = {{The optical properties of pristine and titanium-doped LiNbO3 are modeled from first principles. The dielectric functions are calculated within time-dependent density-functional theory, and a model long-range contribution is employed for the exchange-correlation kernel in order to account for the electron-hole binding. Our study focuses on the influence of substitutional titanium atoms on lithium sites. We show that an increasing titanium concentration enhances the values of the refractive indices and the reflectivity.}}, author = {{Friedrich, Michael and Schmidt, Wolf Gero and Schindlmayr, Arno and Sanna, Simone}}, issn = {{2475-9953}}, journal = {{Physical Review Materials}}, number = {{3}}, publisher = {{American Physical Society}}, title = {{{Optical properties of titanium-doped lithium niobate from time-dependent density-functional theory}}}, doi = {{10.1103/PhysRevMaterials.1.034401}}, volume = {{1}}, year = {{2017}}, } @article{13416, abstract = {{The optical properties of congruent lithium niobate are analyzed from first principles. The dielectric function of the material is calculated within time-dependent density-functional theory. The effects of isolated intrinsic defects and defect pairs, including the NbLi4+ antisite and the NbLi4+−NbNb4+ pair, commonly addressed as a bound polaron and bipolaron, respectively, are discussed in detail. In addition, we present further possible realizations of polaronic and bipolaronic systems. The absorption feature around 1.64 eV, ascribed to small bound polarons [O. F. Schirmer et al., J. Phys.: Condens. Matter 21, 123201 (2009)], is nicely reproduced within these models. Among the investigated defects, we find that the presence of bipolarons at bound interstitial-vacancy pairs NbV−VLi can best explain the experimentally observed broad absorption band at 2.5 eV. Our results provide a microscopic model for the observed optical spectra and suggest that, besides NbLi antisites and Nb and Li vacancies, Nb interstitials are also formed in congruent lithium-niobate samples.}}, author = {{Friedrich, Michael and Schmidt, Wolf Gero and Schindlmayr, Arno and Sanna, Simone}}, issn = {{2475-9953}}, journal = {{Physical Review Materials}}, number = {{5}}, publisher = {{American Physical Society}}, title = {{{Polaron optical absorption in congruent lithium niobate from time-dependent density-functional theory}}}, doi = {{10.1103/PhysRevMaterials.1.054406}}, volume = {{1}}, year = {{2017}}, } @article{13421, author = {{Landmann, M. and Rauls, E. and Schmidt, Wolf Gero}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{15}}, 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}}, volume = {{95}}, year = {{2017}}, } @article{13414, author = {{Riefer, A. and Schmidt, Wolf Gero}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{23}}, title = {{{Solving the Bethe-Salpeter equation for the second-harmonic generation in Zn chalcogenides}}}, doi = {{10.1103/physrevb.96.235206}}, volume = {{96}}, year = {{2017}}, } @article{7481, abstract = {{The electronic band structures of hexagonal ZnO and cubic ZnS, ZnSe, and ZnTe compounds are determined within hybrid-density-functional theory and quasiparticle calculations. It is found that the band-edge energies calculated on the G0W0 (Zn chalcogenides) or GW (ZnO) level of theory agree well with experiment, while fully self-consistent QSGW calculations are required for the correct description of the Zn 3d bands. The quasiparticle band structures are used to calculate the linear response and second-harmonic-generation (SHG) spectra of the Zn–VI compounds. Excitonic effects in the optical absorption are accounted for within the Bethe–Salpeter approach. The calculated spectra are discussed in the context of previous experimental data and present SHG measurements for ZnO.}}, author = {{Riefer, Arthur and Weber, Nils and Mund, Johannes and Yakovlev, Dmitri R. and Bayer, Manfred and Schindlmayr, Arno and Meier, Cedrik and Schmidt, Wolf Gero}}, issn = {{1361-648X}}, journal = {{Journal of Physics: Condensed Matter}}, number = {{21}}, publisher = {{IOP Publishing}}, title = {{{Zn–VI quasiparticle gaps and optical spectra from many-body calculations}}}, doi = {{10.1088/1361-648x/aa6b2a}}, volume = {{29}}, year = {{2017}}, } @article{10026, abstract = {{Congruent lithium niobate and lithium tantalate mixed crystals have been grown over the complete compositional range with the Czochralski method. The structural and vibrational properties of the mixed crystals are studied extensively by x-ray diffraction measurements, Raman spectroscopy, and density functional theory. The measured lattice parameters and vibrational frequencies are in good agreement with our theoretical predictions. The observed dependence of the Raman frequencies on the crystal composition is discussed on the basis of the calculated phonon displacement patterns. The phononic contribution to the static dielectric tensor is calculated by means of the generalized Lyddane-Sachs-Teller relation. Due to the pronounced dependence of the optical response on the Ta concentration, lithium niobate tantalate mixed crystals represent a perfect model system to study the properties of uniaxial mixed ferroelectric materials for application in integrated optics.}}, author = {{Rüsing, Michael and Sanna, Simone and Neufeld, Sergej and Berth, Gerhard and Schmidt, Wolf Gero and Zrenner, Artur and Yu, H. and Wang, Y. and Zhang, H.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, title = {{{Vibrational properties of LiNb1−xTaxO3 mixed crystals}}}, doi = {{10.1103/physrevb.93.184305}}, year = {{2016}}, } @article{10024, abstract = {{The influence of electronic many-body interactions, spin-orbit coupling, and thermal lattice vibrations on the electronic structure of lithium niobate is calculated from first principles. Self-energy calculations in the GW approximation show that the inclusion of self-consistency in the Green function G and the screened Coulomb potential W opens the band gap far stronger than found in previous G0W0 calculations but slightly overestimates its actual value due to the neglect of excitonic effects in W. A realistic frozen-lattice band gap of about 5.9 eV is obtained by combining hybrid density functional theory with the QSGW0 scheme. The renormalization of the band gap due to electron-phonon coupling, derived here using molecular dynamics as well as density functional perturbation theory, reduces this value by about 0.5 eV at room temperature. Spin-orbit coupling does not noticeably modify the fundamental gap but gives rise to a Rashba-like spin texture in the conduction band.}}, author = {{Riefer, Arthur and Friedrich, Michael and Sanna, Simone and Gerstmann, Uwe and Schindlmayr, Arno and Schmidt, Wolf Gero}}, issn = {{2469-9969}}, journal = {{Physical Review B}}, number = {{7}}, publisher = {{American Physical Society}}, title = {{{LiNbO3 electronic structure: Many-body interactions, spin-orbit coupling, and thermal effects}}}, doi = {{10.1103/PhysRevB.93.075205}}, volume = {{93}}, year = {{2016}}, } @article{10025, abstract = {{The phonon dispersions of the ferro‐ and paraelectric phase of LiTaO3 are calculated within density‐functional perturbation theory. The longitudinal optical phonon modes are theoretically derived and compared with available experimental data. Our results confirm the recent phonon assignment proposed by Margueron et al. [J. Appl. Phys. 111, 104105 (2012)] on the basis of spectroscopical studies. A comparison with the phonon band structure of the related material LiNbO3 shows minor differences that can be traced to the atomic‐mass difference between Ta and Nb. The presence of phonons with imaginary frequencies for the paraelectric phase suggests that it does not correspond to a minimum energy structure, and is compatible with an order‐disorder type phase transition.}}, author = {{Friedrich, Michael and Schindlmayr, Arno and Schmidt, Wolf Gero and Sanna, Simone}}, issn = {{1521-3951}}, journal = {{Physica Status Solidi B}}, number = {{4}}, pages = {{683--689}}, publisher = {{Wiley-VCH}}, title = {{{LiTaO3 phonon dispersion and ferroelectric transition calculated from first principles}}}, doi = {{10.1002/pssb.201552576}}, volume = {{253}}, year = {{2016}}, } @article{10027, author = {{Landmann, M. and Rauls, E. and Schmidt, Wolf Gero and Neumann, M. D. and Speiser, E. and Esser, N.}}, issn = {{1098-0121}}, journal = {{Physical Review B}}, title = {{{GaNm-plane: Atomic structure, surface bands, and optical response}}}, doi = {{10.1103/physrevb.91.035302}}, year = {{2015}}, } @article{10029, author = {{Braun, Christian and Sanna, Simone and Schmidt, Wolf Gero}}, issn = {{1932-7447}}, journal = {{The Journal of Physical Chemistry C}}, pages = {{9342--9346}}, title = {{{Liquid Crystal (8CB) Molecular Adsorption on Lithium Niobate Z-Cut Surfaces}}}, doi = {{10.1021/acs.jpcc.5b00894}}, year = {{2015}}, } @article{10031, author = {{Li, Yanlu and Schmidt, Wolf Gero and Sanna, Simone}}, issn = {{1098-0121}}, journal = {{Physical Review B}}, title = {{{Defect complexes in congruentLiNbO3and their optical signatures}}}, doi = {{10.1103/physrevb.91.174106}}, year = {{2015}}, }