@misc{SeiboldBenfattoCastellanietal., author = {Seibold, G{\"o}tz and Benfatto, Lara and Castellani, Claudio and Lorenzana, Jos{\´e}}, title = {Current Correlations in Strongly Disordered Superconductors}, series = {Journal of Superconductivity and Novel Magnetism}, volume = {29}, journal = {Journal of Superconductivity and Novel Magnetism}, number = {3}, doi = {10.1007/s10948-015-3300-6}, pages = {577 -- 580}, language = {en} } @misc{CeaBucheliSeiboldetal., author = {Cea, Tommaso and Bucheli, Daniel and Seibold, G{\"o}tz and Benfatto, Lara and Lorenzana, Jos{\´e} and Castellani, Claudio}, title = {Optical excitation of phase modes in strongly disordered superconductors}, series = {Physical Review B}, volume = {89}, journal = {Physical Review B}, issn = {2469-9969}, doi = {10.1103/PhysRevB.89.174506}, pages = {174506}, abstract = {According to the Goldstone theorem the breaking of a continuous U(1) symmetry comes along with the existence of low-energy collective modes. In the context of superconductivity these excitations are related to the phase of the superconducting (SC) order parameter and for clean systems are optically inactive; that is, single-mode excitations do not directly couple to light. Here we show that for strongly disordered superconductors phase modes acquire a dipole moment and appear as a subgap spectral feature in the optical conductivity. This finding is obtained with both a gauge-invariant random-phase approximation scheme based on a fermionic Bogoliubov-de Gennes state and a prototypical bosonic model for disordered superconductors. In the strongly disordered regime, where the system displays an effective granularity of the SC properties, the optically active dipoles are linked to the isolated SC islands, offering a new perspective for realizing microwave optical devices.}, language = {en} } @misc{LemarieKamlapureBenfattoetal., author = {Lemari{\´e}, Gabriel and Kamlapure, Anand and Benfatto, Lara and Lorenzana, Jos{\´e} and Seibold, G{\"o}tz and Ganguli, S. C. and Raychaudhuri, Pratap and Castellani, Claudio}, title = {Universal scaling of the order-parameter distribution in strongly disordered superconductors}, series = {Physical Review B}, volume = {87}, journal = {Physical Review B}, number = {18}, issn = {2469-9977}, doi = {10.1103/PhysRevB.87.184509}, pages = {184509}, abstract = {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.}, language = {en} } @misc{SeiboldBenfattoCastellanietal., author = {Seibold, G{\"o}tz and Benfatto, Lara and Castellani, Claudio and Lorenzana, Jos{\´e}}, title = {Superfluid Density and Phase Relaxation in Superconductors with Strong Disorder}, series = {Physical Review Letters}, volume = {108}, journal = {Physical Review Letters}, number = {20}, issn = {1092-0145}, doi = {10.1103/PhysRevLett.108.207004}, pages = {207004}, abstract = {We consider the attractive Hubbard model with on-site disorder as a prototype of a disordered superconductor. We solve the Bogoliubov-de Gennes equations on two-dimensional finite clusters at zero temperature and evaluate the electromagnetic response to a vector potential. We find that the standard decoupling between transverse and longitudinal response does not apply in the presence of disorder. Moreover, the superfluid density is strongly reduced by the relaxation of the phase of the order parameter already at mean-field level when disorder is large. We also find that the anharmonicity of the phase fluctuations is strongly enhanced by disorder. Beyond mean field, this provides an enhancement of quantum fluctuations inducing a zero-temperature transition to a nonsuperconducting phase of disordered preformed pairs. Finally, the connection of our findings with the glassy physics for extreme dirty superconductors is discussed.}, language = {en} } @misc{SeiboldBenfattoCastellanietal., author = {Seibold, G{\"o}tz and Benfatto, Lara and Castellani, Claudio and Lorenzana, Jos{\´e}}, title = {Amplitude, density, and current correlations of strongly disordered superconductors}, series = {Physical Review B}, volume = {92}, journal = {Physical Review B}, number = {6}, issn = {2469-9969}, doi = {10.1103/PhysRevB.92.064512}, pages = {064512}, abstract = {We investigate the disorder dependence of the static density, amplitude, and current correlations within the attractive Hubbard model supplemented with onsite disorder. It is found that strong disorder favors a decoupling of density and amplitude correlations due to the formation of superconducting (SC) islands. This emergent granularity also induces an enhancement of the density correlations on the SC islands whereas amplitude fluctuations are most pronounced in the "insulating" regions. While density and amplitude correlations are short ranged at strong disorder, we show that current correlations have a long-range tail due to the formation of percolative current paths in agreement with the constant behavior expected from the analysis of one-dimensional models.}, language = {en} } @misc{SeiboldCastellaniLorenzana, author = {Seibold, G{\"o}tz and Castellani, Claudio and Lorenzana, Jos{\´e}}, title = {Adiabatic transition from a BCS superconductor to a Fermi liquid and phase dynamics}, series = {Physical Review B}, volume = {105}, journal = {Physical Review B}, number = {18}, issn = {2469-9969}, doi = {10.1103/PhysRevB.105.184513}, pages = {184513-1 -- 184513-14}, abstract = {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.}, language = {en} }