Search

We calculate the current response to a static vector potential in disordered superconductors. In contrast to standard BCS theory which violates gauge invariance, it is important here to incorporate the coupling to phase fluctuations in order to obey charge conservation. At strong disorder, where the system breaks up into superconducting islands, the superfluid stiffness is determined by percolative current paths which form via a 'constriction' process from the homogeneous situation. [ABSTRACT FROM AUTHOR]

In underdoped cuprates, both stripes and spiral states may account for the incommensurate spin response observed by elastic neutron scattering experiments. Here, we investigate the respective stability of both textures within the framework of the three-band Hubbard model which we treat within the unrestricted Gutzwiller approximation. Our calculations indicate that for parameter sets appropriate for lanthanum cuprates and small doping nor purely longitudinal stripes nor uniform spirals are stable but stripes with significant spin canting. Indeed at small doping uniform spirals are unstable toward nanoscale phase separation. [ABSTRACT FROM AUTHOR]

We present the time-dependent Gutzwiller approximation as a suitable technique for the calculation of static and dynamic properties of stripes in high- T superconductors. We will especially focus on the magnetic fluctuations induced by such textures and investigate their energy, momentum and doping dependence. For the magnetic dispersion, we find the characteristic 'hour-glass' shape which has been experimentally determined in LSCO and YBCO compounds. Low and high energy incommensurate branches merge at a saddle-point. We discuss the doping dependence of the latter in relation to the structure of the underlying stripe phase. [ABSTRACT FROM AUTHOR]

We discuss the interplay of phonons with electronic correlations in the small amplitude-limit of the time-dependent Gutzwiller approximation. In this approach the time-dependent Lagrangian for the Hubbard model can be computed with a Gutzwiller wave-function in infinite dimensions and subsequently expanded up to quadratic order in density and double occupancy fluctuations. The dynamics of the latter show a strong softening around the metal-insulator transition giving rise to an interesting interplay with phonons which couple to the hopping. [ABSTRACT FROM AUTHOR]

phenomenological model is constructed which can reconcile the simultaneous existence of low-energy Bogoljubov quasiparticles and high-energy electronic order as observed by scanning tunneling microscopy (STM) experiments in cuprates. The theory can account for the high-energy contrast reversal in the STM spectra between positive and negative bias as characteristic for charge-density wave scattering. On the other hand the low-energy Fourier-transform of the local density of states is an even function of bias which provides an alternative to the formation of pair-density waves. [ABSTRACT FROM AUTHOR]