TY - JOUR A1 - Sigmund, Ernst A1 - Seibold, Götz A1 - Bill, Andreas A1 - Wulf, Ulrich A1 - Isenmann, G. A1 - Essl, W. T1 - Dynamische Eigenschaften von Festkörpern und Molekularen Strukturen Y1 - 1995 ER - TY - GEN A1 - Bill, Andreas A1 - Hizhnyakov, Vladimir A1 - Kremer, Reinhard K. A1 - Seibold, Götz A1 - Shelkan, Aleksander A1 - Sherman, Aleksei T1 - Phase Separation and Pairing Fluctuations in Oxide Materials T2 - Condensed Matter N2 - The microscopic mechanism of charge instabilities and the formation of inhomogeneous states in systems with strong electron correlations is investigated. We demonstrate that within a strong coupling expansion the single-band Hubbard model shows an instability towards phase separation and extend the approach also for an analysis of phase separation in the Hubbard-Kanamori hamiltonian as a prototypical multiband model. We study the pairing fluctuations on top of an inhomogeneous stripe state where superconducting correlations in the extended s-wave and d-wave channels correspond to (anti)bound states in the two-particle spectra. Whereas extended s-wave fluctuations are relevant on the scale of the local interaction parameter U, we find that d-wave fluctuations are pronounced in the energy range of the active subband which crosses the Fermi level. As a result, low energy spin and charge fluctuations can transfer the d-wave correlations from the bound states to the low energy quasiparticle bands. Our investigations therefore help to understand the coexistence of stripe correlations and d-wave superconductivity in cuprates. KW - phase separation KW - cuprate superconductors KW - electronic correlations Y1 - 2020 UR - https://www.mdpi.com/2410-3896/5/4/65/htm U6 - https://doi.org/10.3390/condmat5040065 SN - 2410-3896 VL - 5 IS - 4 ER - TY - GEN A1 - Martens, Christian A1 - Bill, Andreas A1 - Seibold, Götz T1 - Phase separation and proximity effects in itinerant ferromagnet/superconductor heterostructures T2 - Physical Review B N2 - Heterostructures made of itinerant ferromagnets and superconductors are studied. In contrast to most previous models, ferromagnetism is not enforced by an effective Zeeman field but induced in a correlated single-band model (CSBM) that displays itinerant ferromagnetism as a mean-field ground state. In this model superconductivity and magnetism are both calculated self-consistently. We calculate the magnitude of the magnetization, the superconducting correlations, and variations of the charge density self-consistently for a superconducting-magnetic bilayer by solving the Bogoliubov–de Gennes equations on a two-dimensional lattice. We determine all three quantities as a function of the Coulomb repulsion U and the ferromagnetic exchange interaction J. The CSBM displays a variety of features not present in the Zeeman exchange model—for example, the occurrence of electronic phase separation and the competition of magnetic and superconducting orders far away from the interface. KW - charge order KW - Exchange interaction KW - Ferromagnetism KW - Local density of states KW - Microphase separation KW - Proximity effect KW - Superconducting order parameter Y1 - 2018 U6 - https://doi.org/10.1103/PhysRevB.98.174513 SN - 2469-9969 SN - 1095-3795 VL - 98 IS - 17 ER - TY - CHAP A1 - Bill, Andreas A1 - Hizhnyakov, Vladimir A1 - Seibold, Götz ED - Bussmann-Holder, Annette ED - Keller, Hugo ED - Bianconi, Antonio T1 - Electronic Phase Separation and Electron–Phonon Coupling in Cuprate Superconductors T2 - High-Tc Copper Oxide Superconductors and Related Novel Materials N2 - Nanoscale electronic inhomogeneities are nowadays a well established feature of high-temperature superconductors, most prominently exemplified by the observation of charge-ordered states in a large number of cuprate materials. These inhomogeneities have profound consequences for the electron–phonon coupling since they allow for long-range pairing interactions due to the reduced screening supplemented by the enhancement of the electron–phonon vertex due to strong correlations. In this chapter we review the particular contribution of the Stuttgart-Tartu-Cottbus group to this field and discuss how the current status of experimental results provides affirmation to their ideas. KW - Strongly Correlated Systems KW - Optical and Electronic Materials KW - Nanochemistry KW - Ceramics KW - Spectroscopy and Microscopy KW - Superconductivity KW - Glass KW - Composites KW - Natural Materials Y1 - 2017 UR - http://link.springer.com/chapter/10.1007/978-3-319-52675-1_1 SN - 978-3-319-52674-4 SN - 978-3-319-52675-1 U6 - https://doi.org/10.1007/978-3-319-52675-1_1 SP - 1 EP - 14 PB - Springer International Publishing CY - Cham ER - TY - CHAP A1 - Bill, Andreas A1 - Hizhnyakov, Vladimir A1 - Seibold, Götz A1 - Sigmund, Ernst ED - Bussmann-Holder, Annette T1 - Electronic Inhomogeneities and Pairing from Unscreened Interactions in High-Tc Superconductors T2 - High-Tc Superconductors and Related Transition Metal Oxides Y1 - 2007 SN - 978-3-540-71022-6 SP - 143 EP - 156 PB - Springer CY - Berlin [u.a.] ER - TY - JOUR A1 - Bill, Andreas A1 - Hizhnyakov, Vladimir A1 - Nevedrov, D. A1 - Seibold, Götz A1 - Sigmund, Ernst T1 - Electronic inhomogeneities, electron-lattice and pairinginteractions in high-Tc superconductors Y1 - 1997 ER -