TY - JOUR A1 - Guenther, Falk A1 - Seibold, Götz A1 - Lorenzana, José T1 - Quantum Lifshitz point in the infinite dimensional Hubbard model Y1 - 2007 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 - Seibold, Götz A1 - Capati, Matteo A1 - Grilli, Marco A1 - Di Castro, Carlo A1 - Grilli, Marco A1 - Lorenzana, José T1 - Hidden ferronematic order in underdoped cuprates T2 - Physical Review B N2 - We study a model for low-doped cuprates where holes aggregate into oriented stripe segments which have a magnetic vortex and antivortex at the extremes. We argue that due to the interaction between segments a ferronematic state with macroscopic polarization is stabilized. This state can be characterized as a charge nematic which, due to the net polarization, breaks inversion symmetry and also exhibits an incommensurate spin modulation. Our calculation can reproduce the doping-dependent spin structure factor of lanthanum cuprates in excellent agreement with experiment and allows to rationalize experiments in which the incommensurability has an order-parameter-like temperature dependence. Y1 - 2013 UR - http://journals.aps.org/prb/abstract/10.1103/PhysRevB.87.035138 U6 - https://doi.org/10.1103/PhysRevB.87.035138 SN - 2469-9969 VL - 87 IS - 3 SP - 035138 ER - TY - GEN A1 - Noatschk, Katharina A1 - Martens, Christian A1 - Seibold, Götz T1 - Time-Dependent Gutzwiller Approximation: Theory and Applications T2 - Journal of Superconductivity and Novel Magnetism N2 - The time-dependent Gutzwiller approximation is rederived on the basis of a variational wave function which is a direct product of a Slater determinant and a coherent state. The latter can be related to the slave-boson formulation by Kotliar and Ruckenstein, and our approach offers a convenient way to generalize the theory towards the implementation of symmetry-broken states and the study of non-equilibrium phenomena. We discuss the concept with regard to applications in the linear response limit and for quenched antiferromagnetic order for which we evaluate the optical conductivity in non-equilibrium situations. KW - Hubbard model KW - Gutzwiller approximation KW - Non-equilibrium Y1 - 2020 UR - https://link.springer.com/article/10.1007/s10948-019-05406-z#Sec1 U6 - https://doi.org/10.1007/s10948-019-05406-z VL - 33 IS - 8 SP - 2389 EP - 2393 ER - TY - JOUR A1 - Müller, Sebastian A1 - Seibold, Götz A1 - Schmeißer, Dieter ED - Vierhaus, Heinrich Theodor T1 - Preparation and Characterization of TiO2 Thin Films and Cr and Co Doped TiO2 Thin Films Y1 - 2007 ER - TY - JOUR A1 - Seibold, Götz A1 - Lorenzana, José T1 - Doping dependence of spin excitations in the stripe phase of high-Tc superconductors Y1 - 2006 ER - TY - GEN A1 - Seibold, Götz A1 - Di Castro, Carlo A1 - Grilli, Marco A1 - Lorenzana, José T1 - Spin excitations of ferronematic order in underdoped cuprate superconductors T2 - Scientific reports N2 - High-temperature superconductors exhibit a characteristic hourglass-shaped spectrum of magnetic fluctuations which most likely contribute to the pairing glue in the cuprates. Recent neutron scattering experiments in strongly underdoped compounds have revealed a significant low energy anisotropy of these fluctuations which we explain by a model in which topological defects of the antiferromagnet clump to producing domain wall segments with ferronematic order. This state does not invoke global charge order but breaks C4 rotational and inversion symmetry. The incommensurability of the low doping charge-disordered state is in good agreement with experiment and interpolates smoothly with the incommensurability of the stripe phase at higher doping. Within linear spin-wave theory the dynamic structure factor is in very good agreement with inelastic neutron scattering data and can account for the observed energy dependent anisotropy. Y1 - 2014 UR - http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4060504/ U6 - https://doi.org/10.1038/srep05319 SN - 2045-2322 IS - 4 SP - 5319 ER - TY - GEN A1 - Markiewicz, Richard S. A1 - Lorenzana, José A1 - Seibold, Götz T1 - Gutzwiller magnetic phase diagram of the undoped $ t- t' -U $ Hubbard model Y1 - 2010 ER - TY - GEN A1 - Bünemann, Jörg A1 - Capone, Michael A1 - Lorenzana, José A1 - Seibold, Götz T1 - Linear-response dynamics from the time-dependent Gutzwiller approximation T2 - New Journal of Physics N2 - Within a Lagrangian formalism, we derive the time-dependent Gutzwiller approximation for general multi-band Hubbard models. Our approach explicitly incorporates the coupling between time-dependent variational parameters and a time-dependent density matrix from which we obtain dynamical correlation functions in the linear-response regime. Our results are illustrated for the one-band model where we show that the interacting system can be mapped to an effective problem of fermionic quasiparticles coupled to 'doublon' (double occupancy) bosonic fluctuations. The latter have an energy on the scale of the on-site Hubbard repulsion U in the dilute limit but become soft at the Brinkman–Rice transition, which is shown to be related to an emerging conservation law of doublon charge and the associated gauge invariance. Coupling with the boson mode produces a structure in the charge response and we find that a similar structure appears in dynamical mean-field theory. Y1 - 2013 UR - http://iopscience.iop.org/article/10.1088/1367-2630/15/5/053050 SN - 1367-2630 VL - 15 ER - TY - GEN A1 - Seibold, Götz A1 - Grilli, Marco A1 - Lorenzana, José T1 - Stripes in cuprate superconductors: Excitations and dynamic dichotomy T2 - Physica C: Superconductivity N2 - We present a short account of the present experimental situation of stripes in cuprates followed by a review of our present understanding of their ground state and excited state properties. Collective modes, the dynamical structure factor, and the optical conductivity of stripes are computed using the time-dependent Gutzwiller approximation applied to realistic one band and three band Hubbard models, and are found to be in excellent agreement with experiment. On the other hand, experiments like angle-resolved photoemission and scanning tunneling microscopy show the coexistence of stripes at high energies with Fermi liquid quasiparticles at low energies. We show that a phenomenological model going beyond mean-field can reconcile this dynamic dichotomy. Y1 - 2012 UR - http://www.sciencedirect.com/science/article/pii/S0921453412001864 U6 - https://doi.org/10.1016/j.physc.2012.03.072 SN - 0921-4534 VL - 481 SP - 132 EP - 145 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 - GEN A1 - Seibold, Götz A1 - Benfatto, Lara A1 - Castellani, Claudio A1 - Lorenzana, José T1 - Current Correlations in Strongly Disordered Superconductors T2 - Journal of Superconductivity and Novel Magnetism Y1 - 2016 UR - http://link.springer.com/article/10.1007%2Fs10948-015-3300-6 U6 - https://doi.org/10.1007/s10948-015-3300-6 VL - 29 IS - 3 SP - 577 EP - 580 ER - TY - JOUR A1 - Seibold, Götz A1 - Lorenzana, José T1 - Stability of metallic stripes in the extended one-band Hubbard model Y1 - 2004 ER - TY - GEN A1 - Markiewicz, Richard S. A1 - Lorenzana, José A1 - Seibold, Götz A1 - Bansil, Arun T1 - Short range smectic order driving long range nematic order: example of cuprates T2 - Scientific reports Y1 - 2016 UR - http://www.nature.com/articles/srep19678 U6 - https://doi.org/10.1038/srep19678 SN - 2045-2322 VL - 6 SP - 19678 ER - TY - JOUR A1 - Günther, Falk A1 - Seibold, Götz T1 - Time-dependent Gutzwiller theory of pair fluctuations in the Hubbard model Y1 - 2007 ER - TY - GEN A1 - Benfatto, Lara A1 - Castellani, Claudio A1 - Seibold, Götz T1 - Linear and nonlinear current response in disordered d-wave superconductors T2 - Physical Review B N2 - We present a detailed theoretical investigation of the linear and nonlinear optical response in a model system for a disordered d-wave superconductor. By evaluating the quasiparticle contribution (BCS response) we show that for both quantities the gap symmetry considerably changes the paradigm of the optical response as compared to the conventional s-wave case. For what concerns the linear response our findings agree with previous work showing that in strongly disordered d-wave superconductors a large fraction of uncondensed spectral weight survives below Tc, making the optical absorption around the gap-frequency scale almost unchanged with respect to the normal state. Our numerical results are in excellent quantitative agreement with experiments in overdoped cuprates. In the nonlinear regime we focus on the third-harmonic generation (THG), finding that, as already established for the s-wave case, in general a large THG is triggered by disorder-activated paramagnetic processes. However, in the d-wave case the BCS response is monotonously increasing in frequency, losing any signature of THG enhancement when the THz pump frequency ω matches the gap maximum Δ, a hallmark of previous experiments in conventional s-wave superconductors. Our findings, along with the mild polarization dependence of the response, provide an explanation for recent THG measurements in cuprates, setting the framework for the theoretical understanding of nonlinear effects in unconventional cuprates. KW - Superconducting order parameter KW - Superfluid density KW - High-temperature superconductors KW - Superconductivity KW - Drude model KW - Numerical techniques KW - Reflectivity KW - Terahertz spectroscopy Y1 - 2023 UR - https://journals.aps.org/prb/abstract/10.1103/PhysRevB.108.134508 U6 - https://doi.org/10.1103/PhysRevB.108.134508 SN - 2469-9969 SN - 2469-9950 VL - 108 SP - 134508-1 EP - 134508-15 ER - TY - GEN A1 - Seibold, Götz A1 - Castellani, Claudio A1 - Di Castro, Carlo A1 - Grilli, Marco T1 - Fermi surface and photoemission lineshape of incommensurate CDW systems Y1 - 2000 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 - JOUR A1 - Seibold, Götz A1 - Grilli, Marco A1 - Lorenzana, José T1 - Checkerboard and stripe inhomogeneities in cuprates JF - Physical review B Y1 - 2007 SN - 1550-235X VL - 75 IS - 10 SP - 10050(R) ER - TY - GEN A1 - Ugenti, S. A1 - Cini, M. A1 - Seibold, Götz A1 - Lorenzana, José A1 - Perfetto, E. A1 - Stefanucci, G. T1 - Particle-particle response function as a probe for electronic correlations in the p-d Hubbard model Y1 - 2010 ER -