1,668 research outputs found

    Quantum criticality with a twist - interplay of correlations and Kohn anomalies in three dimensions

    Full text link
    A general understanding of quantum phase transitions in strongly correlated materials is still lacking. By exploiting a cutting-edge quantum many-body approach, the dynamical vertex approximation, we make an important progress, determining the quantum critical properties of the antiferromagnetic transition in the fundamental model for correlated electrons, the Hubbard model in three dimensions. In particular, we demonstrate that -in contradiction to the conventional Hertz-Millis-Moriya theory- its quantum critical behavior is driven by the Kohn anomalies of the Fermi surface, even when electronic correlations become strong.Comment: 6 pages, 4 figures (8 pages Supplemental Material

    Quasi-particle dephasing time in disordered d-wave superconductors

    Full text link
    We evaluate the low-temperature cutoff for quantum interference 1/tf induced in a d-wave superconductor by the diffusion enhanced quasiparticle interactions in the presence of disorder. We carry out our analysis in the framework of the non-linear sigma-model which allows a direct calculation of 1/tf, as the mass of the transverse modes of the theory. Only the triplet amplitude in the particle-hole channel and the Cooper amplitude with is pairing symmetry contribute to 1/tf. We discuss the possible relevance of our results to the present disagreement between thermal transport data in cuprates and the localization theory for d-wave quasiparticles

    Coherence length in superconductors from weak to strong coupling

    Full text link
    We study the evolution of the superconducting coherence length ξ0\xi_0 from weak to strong coupling, both within a s-wave and a d-wave lattice model. We show that the identification of ξ0\xi_0 with the Cooper-pair size ξpair\xi_{pair} in the weak-coupling regime is meaningful only for a fully-gapped (e.g., s-wave) superconductor. Instead in the d-wave superconductor, where ξpair\xi_{pair} diverges, we show that ξ0\xi_0 is properly defined as the characteristic length scale for the correlation function of the modulus of the superconducting order parameter. The strong-coupling regime is quite intriguing, since the interplay between particle-particle and particle-hole channel is no more negligible. In the case of s-wave pairing, which allows for an analytical treatment, we show that ξ0\xi_0 is of order of the lattice spacing at finite densities. In the diluted regime ξ0\xi_0 diverges, recovering the behavior of the coherence length of a weakly interacting effective bosonic system. Similar results are expected to hold for d-wave superconductors.Comment: 11 pages, 5 figures. Two appendices and new references adde