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 - TY - JOUR A1 - Sigmund, Ernst A1 - Hizhnyakov, Vladimir A1 - Seibold, Götz T1 - Electronic Phase Separation in High-Tc Superconductors Y1 - 1994 ER - TY - JOUR A1 - Seibold, Götz A1 - Sigmund, Ernst A1 - Hizhnyakov, Vladimir T1 - Spin-cluster states in CuO2 planes JF - Physical review B Y1 - 1993 SN - 0556-2805 VL - 48 IS - 10 SP - 7537 EP - 7544 ER - TY - CHAP A1 - Sigmund, Ernst A1 - Hizhnyakov, Vladimir A1 - Seibold, Götz T1 - Percolative Phase Separation and High-Tc superconductivity T2 - Proceedings of the Workshop on Phase Separation in Cuprate Semiconductors, Erice, Italy, 1992 Y1 - 1993 SN - 981-02-1274-7 SP - 46 EP - 66 PB - World Scientific CY - Singapore [u.a.] 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 - Hizhnyakov, Vladimir A1 - Seibold, Götz T1 - Nanoscale phase separation in cuprate superconductors T2 - Physica C: Superconductivity and its Applications N2 - 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. In this contribution we review the particular contribution of the Stuttgart-Tartu-Cottbus group to this field, which has been largely stimulated by intense discussion with K. Alex Müller. The original scenario, which was based on the formation of a percolative electronic network, is substantiated by a microscopic analysis of the clustering of magnetic polarons within the one-band Hubbard model. KW - Cuprates KW - Superconductors KW - Phase separation KW - Electronic inhomogeneities Y1 - 2023 UR - https://www.sciencedirect.com/science/article/pii/S0921453423001004 U6 - https://doi.org/10.1016/j.physc.2023.1354309 SN - 1873-2143 VL - 612 SP - 1 EP - 7 ER - TY - JOUR A1 - Sigmund, Ernst A1 - Hizhnyakov, Vladimir A1 - Seibold, Götz T1 - Phase-Separation in High-Tc Superconductors JF - Physica C : Superconductivity Y1 - 1994 SN - 0921-4534 VL - Vol. 235–240 IS - 1 SP - 253 EP - 256 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 - Shelkan, Aleksander A1 - Sigmund, Ernst A1 - Hizhnyakov, Vladimir A1 - Seibold, Götz ED - Kaplan, Michael D. T1 - Free and spin-polaron states in high-Tc superconductor T2 - Proceedings of the NATO Advanced Research Workshop on Colossal Magnetoresistance and Vibronic Interactions and the XVth International Jahn-Teller Symposium on Vibronic Interactions in Crystals and Molecules, Boston, August 16 - 22, 2000 Y1 - 2001 SN - 1-402-00044-8 SP - 349 EP - 356 PB - Kluwer CY - Dordrecht [u.a.] ER - TY - JOUR A1 - Seibold, Götz A1 - Letz, M. A1 - Sigmund, Ernst A1 - Hizhnyakov, Vladimir T1 - Mean-Field Theories of Spin-Cluster States in copper oxide planes Y1 - 1994 ER - TY - JOUR A1 - Seibold, Götz A1 - Sigmund, Ernst A1 - Hizhnyakov, Vladimir T1 - Spin-Polaron Formation and Phase Separation Y1 - 1996 ER - TY - JOUR A1 - Seibold, Götz A1 - Sigmund, Ernst A1 - Hizhnyakov, Vladimir T1 - Unrestricted slave-boson mean-field approximation for the two-dimensional Hubbard model JF - Physical review Y1 - 1998 SN - 0556-2805 VL - 57 IS - 12 SP - 6937 EP - 6942 ER - TY - CHAP A1 - Hizhnyakov, Vladimir A1 - Sigmund, Ernst A1 - Seibold, Götz T1 - Polaron Formation and Percolative Phase Separation T2 - Phase Separation in Cuprate Superconductors Y1 - 1994 SN - 3-540-57681-9 SP - 50 EP - 65 PB - Springer CY - Berlin [u.a.] ER -