TY - JOUR A1 - Schmeißer, Dieter A1 - Seibold, Götz A1 - Reif, Jürgen T1 - Nano-scaled Dielectric Barriers (NanoDieB) for CMOS compatible Si-technologies JF - Forum der Forschung KW - nano-scaled KW - dielectric KW - CMOS Y1 - 2006 SN - 0947-6989 IS - 19 SP - 131 EP - 136 ER - TY - GEN A1 - Seibold, Götz T1 - On the Evaluation of Higher-Harmonic-Current Responses for High-Field Spectroscopies in Disordered Superconductors T2 - Condensed Matter N2 - We discuss a formalism that allows for the calculation of a higher-harmonic-current response to a strong applied electric field for disordered superconducting systems described on the basis of tight-binding models with on- and/or intersite interactions. The theory is based on an expansion of the density matrix in powers of the field amplitudes, where we solve the equation of motion for the individual components. This allows the evaluation of higher-order response functions on significantly larger lattices than one can achieve with a previously used approach, which is based on a direct temporal integration of the equation of motion for the complete density matrix. In the case of small lattices, where both methods can be applied by including also the contribution of collective modes, we demonstrate the agreement of the corresponding results. KW - superconductivity KW - third-harmonic generation KW - disorder Y1 - 2023 UR - https://www.mdpi.com/2410-3896/8/4/95 U6 - https://doi.org/10.3390/condmat8040095 SN - 2410-3896 VL - 8 IS - 4 SP - 1 EP - 16 ER - TY - GEN A1 - Seibold, Götz A1 - Pickhardt, Michael T1 - Lapse of time effects on tax evasion in an agent-based econophysics model T2 - Physica A: Statistical Mechanics and its Applications N2 - We investigate an inhomogeneous Ising model in the context of tax evasion dynamics where different types of agents are parameterized via local temperatures and magnetic fields. In particular, we analyze the impact of lapse of time effects (i.e. backauditing) and endogenously determined penalty rates on tax compliance. Both features contribute to a microfoundation of agent-based econophysics models of tax evasion. Y1 - 2013 UR - http://www.sciencedirect.com/science/article/pii/S0378437113000307 U6 - https://doi.org/10.1016/j.physa.2013.01.016 SN - 0378-4371 VL - 392 IS - 9 SP - 2079 EP - 2087 ER - 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 - JOUR A1 - Seibold, Götz A1 - Sigmund, Ernst T1 - Gutzwiller and Slave-Boson Methods for Intersite Coulomb Interactions Y1 - 1996 ER - TY - THES A1 - Seibold, Götz T1 - Spin-polarisierte Quasiteilchen in der Hochtemperatursupraleitung Y1 - 1995 PB - Aachen : Shaker ER - TY - JOUR A1 - Ruckh, R. A1 - Seibold, Götz A1 - Sigmund, Ernst T1 - Influence of quantum fluctuations on solitary-wave acoustic polaron motion Y1 - 1993 ER - TY - GEN A1 - Seibold, Götz A1 - Udina, Mattia A1 - Castellani, Claudio A1 - Benfatto, Lara T1 - Third harmonic generation from collective modes in disordered superconductors T2 - Physical Review B N2 - Recent experiments with strong THz fields in both conventional and unconventional superconductors have clearly evidenced a marked third-harmonic generation below the superconducting temperature Tc. Its interpretation challenged substantial theoretical work aimed at establishing the relative efficiency of quasiparticle excitations and collective modes in triggering such a resonant response. Here we compute the nonlinear current by implementing a time-dependent Bogoljubov–de Gennes approach, with the twofold aim to account nonperturbatively for the effect of local disorder, and to include the contribution of all collective modes, i.e., superconducting amplitude (Higgs) and phase fluctuations, and charge fluctuations. We show that, in agreement with previous work, already at small disorder the quasiparticle response is dominated by paramagnetic effects. We further demonstrate that paramagnetic processes mediate also the response of all collective modes, with a substantial contribution of charge/phase fluctuations. These processes, which have been overlooked so far, turn out to dominate the third-order current at strong disorder. In addition, we show that disorder strongly influences the polarization dependence of the nonlinear response, with a marked difference between the clean and the disordered case. Our results are particularly relevant for recent experiments in cuprates, whose band structure is in a first approximation reproduced by our lattice model. KW - High-order harmonic generation KW - Impurities in superconductors KW - Optical & microwave phenomena KW - Quasiparticles & collective excitations KW - Superconductivity KW - Disordered systems KW - Higgs bosons KW - Bogoliubov-de Gennes equations Y1 - 2021 UR - https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.014512 U6 - https://doi.org/10.1103/PhysRevB.103.014512 VL - 103 IS - 1 ER - TY - GEN A1 - Seibold, Götz A1 - Castellani, Claudio A1 - Lorenzana, José T1 - Adiabatic transition from a BCS superconductor to a Fermi liquid and phase dynamics T2 - Physical Review B N2 - We investigate the physics of an adiabatic transition from a BCS superconductor to a Fermi liquid for an exponentially slow decreasing pairing interaction. We show that, depending on the order of the thermodynamic limit and large times, a situation can arise in which the Fermi liquid keeps a memory of the parent BCS state. Furthermore, a time inversion of the interaction, supplemented by a manipulation analogous to a spin-/photon-echo experiment, allows us to recover the parent BCS state. Moreover, we study the evolution of the order parameter phase ϕ in transforming the BCS superconductor to a conventional metal. Since the global phase is the conjugate variable of the density, we explicitly show how to use the dynamics of ϕ together with gauge invariance to build up the noninteracting chemical potential away from particle-hole symmetry. We further analyze the role of ϕ in restoring the gauge-invariant current response when the noninteracting Fermi liquid is approached starting from a BCS superconductor in the presence of an external vector field. KW - Superconductivity KW - Nonequilibrium systems KW - Adiabatic approximation KW - BCS theory KW - Gauge symmetries KW - Variational approach Y1 - 2022 UR - https://journals.aps.org/prb/abstract/10.1103/PhysRevB.105.184513 U6 - https://doi.org/10.1103/PhysRevB.105.184513 SN - 2469-9969 VL - 105 IS - 18 SP - 184513-1 EP - 184513-14 ER - TY - GEN A1 - Caprara, Sergio A1 - Di Castro, Carlo A1 - Mirarchi, Giovanni A1 - Seibold, Götz A1 - Grilli, Marco T1 - Dissipation-driven strange metal behavior T2 - Communications Physics N2 - Anomalous metallic properties are often observed in the proximity of quantum critical points, with violation of the Fermi Liquid paradigm. We propose a scenario where, near the quantum critical point, dynamical fluctuations of the order parameter with finite correlation length mediate a nearly isotropic scattering among the quasiparticles over the entire Fermi surface. This scattering produces a strange metallic behavior, which is extended to the lowest temperatures by an increase of the damping of the fluctuations. We phenomenologically identify one single parameter ruling this increasing damping when the temperature decreases, accounting for both the linear-in-temperature resistivity and the seemingly divergent specific heat observed, e.g., in high-temperature superconducting cuprates and some heavy-fermion metals. KW - Electronic properties and materials KW - Superconducting properties and materials Y1 - 2022 UR - https://www.nature.com/articles/s42005-021-00786-y U6 - https://doi.org/10.1038/s42005-021-00786-y SN - 2399-3650 IS - 5 SP - 1 EP - 7 ER - TY - GEN A1 - Seibold, Götz A1 - Arpaia, Riccardo A1 - Ying Ying, Peng A1 - Fumagalli, Roberto A1 - Braicovich, Lucio A1 - Di Castro, Carlo A1 - Grilli, Marco A1 - Ghiringhelli, Giacomo Claudio A1 - Caprara, Sergio T1 - Strange metal behaviour from charge density fluctuations in cuprates T2 - Communications Physics N2 - Besides the mechanism responsible for high critical temperature superconductivity, the grand unresolved issue of the cuprates is the occurrence of a strange metallic state above the so-called pseudogap temperature T*. Even though such state has been successfully described within a phenomenological scheme, the so-called Marginal Fermi-Liquid theory, a microscopic explanation is still missing. However, recent resonant X-ray scattering experiments identified a new class of charge density fluctuations characterized by low characteristic energies and short correlation lengths, which are related to the well-known charge density waves. These fluctuations are present over a wide region of the temperature-vs-doping phase diagram and extend well above T*. Here we investigate the consequences of charge density fluctuations on the electron and transport properties and find that they can explain the strange metal phenomenology. Therefore, charge density fluctuations are likely the long-sought microscopic mechanism underlying the peculiarities of the metallic state of cuprates. KW - Electronic properties and materials KW - Superconducting properties and materials Y1 - 2021 UR - https://www.nature.com/articles/s42005-020-00505-z U6 - https://doi.org/10.1038/s42005-020-00505-z SN - 2399-3650 VL - 4 SP - 1 EP - 6 ER - TY - GEN A1 - Seibold, Götz A1 - Benfatto, Lara A1 - Castellani, Claudio T1 - Application of the Mattis-Bardeen theory in strongly disordered superconductors T2 - Physical Review B N2 - The low-energy optical conductivity of conventional superconductors is usually well described by Mattis-Bardeen (MB) theory, which predicts the onset of absorption above an energy corresponding to twice the superconducing (SC) gap parameter Δ. Recent experiments on strongly disordered superconductors have challenged the application of the MB formulas due to the occurrence of additional spectral weight at low energies below 2Δ. Here we identify three crucial items that have to be included in the analysis of optical-conductivity data for these systems: (a) the correct identification of the optical threshold in the Mattis-Bardeen theory and its relation with the gap value extracted from the measured density of states, (b) the gauge-invariant evaluation of the current-current response function needed to account for the optical absorption by SC collective modes, and (c) the inclusion into the MB formula of the energy dependence of the density of states present already above Tc. By computing the optical conductivity in the disordered attractive Hubbard model, we analyze the relevance of all these items, and we provide a compelling scheme for the analysis and interpretation of the optical data in real materials. KW - Superconductivity KW - Superconductivity fluctuations KW - Impurities in superconductors Y1 - 2017 UR - https://journals.aps.org/prb/abstract/10.1103/PhysRevB.96.144507 U6 - https://doi.org/10.1103/PhysRevB.96.144507 VL - 96 IS - 14 SP - 144507 ER - TY - GEN A1 - Noatschk, Katharina A1 - Hofmann, E. V. S. A1 - Dabrowski, J. A1 - Curson, N. J. A1 - Schröder, Thomas A1 - Klesse, Wolfgang Matthias A1 - Seibold, Götz T1 - Ge(001) surface reconstruction with Sn impurities T2 - Surface Science N2 - Defects play an important role for surface reconstructions and therefore also influence the substrate growth. In this work we present a first principle calculation for the Ge(001) surface without and with tin impurities incorporated into the top surface layer. By mapping the system onto an Ising-type model, with interaction constants taken from density functional theory, the stability of the surface reconstructions under the influence of different concentrations of tin impurities is explored. This approach allows us to simulate the possible phase transitions for the different surface reconstructions including the local structure around the tin impurity atoms. In addition, we compare our theoretical results with experimental STM images on clean and Sn-doped Ge(100) surfaces. KW - Gesn KW - DFT KW - Monte carlo simulations KW - Surface reconstruction KW - Impurities Y1 - 2021 UR - https://www.sciencedirect.com/science/article/pii/S0039602821001163?dgcid=author U6 - https://doi.org/10.1016/j.susc.2021.121912 VL - 713 SP - 1 EP - 8 ER - TY - GEN A1 - Oelsen, E. von A1 - Di Ciolo, A. A1 - Lorenzana, José A1 - Seibold, Götz A1 - Grilli, Marco T1 - Phonon renormalization from local and transitive electron-latticecouplings in strongly correlated systems Y1 - 2010 ER - TY - JOUR A1 - Lorenzana, José A1 - Seibold, Götz A1 - Ortix, C. A1 - Grilli, Marco T1 - Competing orders in FeAs layers Y1 - 2008 ER - TY - GEN A1 - Tea, C. A1 - Castellani, Claudio A1 - Seibold, Götz A1 - Benfatto, Lara T1 - Nonrelativistic Dynamics of the Amplitude (Higgs) Mode in Superconductors T2 - Physical Review Letters Y1 - 2015 UR - https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.115.157002 U6 - https://doi.org/http://dx.doi.org/10.1103/PhysRevLett.115.157002 SN - 1079-7114 VL - 115 SP - 157002 ER - TY - GEN A1 - Di Ciolo, A. A1 - Lorenzana, José A1 - Grilli, Marco A1 - Seibold, Götz T1 - Charge instabilities and electron-phonon interaction in the Hubbard-Holstein model T2 - Physical Review B KW - strongly correlated systems Y1 - 2009 SN - 1550-235X VL - 79 SP - 085101 ER - TY - GEN A1 - Mirarchi, Giovanni A1 - Seibold, Götz A1 - Di Castro, Carlo A1 - Grilli, Marco A1 - Caprara, Sergio T1 - The Strange-Metal Behavior of Cuprates T2 - Condensed Matter N2 - Recent resonant X-ray scattering experiments on cuprates allowed to identify a new kind of collective excitations, known as charge density fluctuations, which have finite characteristic wave vector, short correlation length and small characteristic energy. It was then shown that these fluctuations provide a microscopic scattering mechanism that accounts for the anomalous transport properties of cuprates in the so-called strange-metal phase and are a source of anomalies in the specific heat. In this work, we retrace the main steps that led us to attributing a central role to charge density fluctuations in the strange-metal phase of cuprates, discuss the state of the art on the issue and provide an in-depth analysis of the contribution of charge density fluctuations to the specific heat. KW - high-temperature superconductors KW - cuprates KW - charge density fluctuations KW - strange metal KW - dynamical quantum criticality Y1 - 2022 UR - https://www.mdpi.com/2410-3896/7/1/29/htm U6 - https://doi.org/10.3390/condmat7010029 SN - 2410-3896 VL - 7 IS - 1 SP - 1 EP - 17 ER - TY - GEN A1 - Lemarié, Gabriel A1 - Kamlapure, Anand A1 - Benfatto, Lara A1 - Lorenzana, José A1 - Seibold, Götz A1 - Ganguli, S. C. A1 - Raychaudhuri, Pratap A1 - Castellani, Claudio T1 - Universal scaling of the order-parameter distribution in strongly disordered superconductors T2 - Physical Review B N2 - We investigate theoretically and experimentally the statistical properties of the inhomogeneous order-parameter distribution (OPD) at the verge of the superconductor-insulator transition (SIT). We find within two prototype fermionic and bosonic models for disordered superconductors that one can identify a universal rescaling of the OPD. By performing scanning-tunneling microscopy experiments in three samples of NbN with increasing disorder we show that such a rescaling also describes the experimental data with excellent accuracy. These results can provide a breakthrough in our understanding of the SIT. Y1 - 2013 UR - http://journals.aps.org/prb/abstract/10.1103/PhysRevB.87.184509 U6 - https://doi.org/10.1103/PhysRevB.87.184509 SN - 2469-9977 VL - 87 IS - 18 SP - 184509 ER - TY - GEN A1 - Mondal, Mintu A1 - Kumar, Sanjeev A1 - Chand, Madhavi A1 - Kamlapure, Anand A1 - Saraswat, Garima A1 - Seibold, Götz A1 - Benfatto, Lara A1 - Raychaudhuri, Pratap T1 - Role of the Vortex-Core Energy on the Berezinskii-Kosterlitz-Thouless Transition in Thin Films of NbN Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevLett.107.217003 ER -