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J. Lages

Publications and source records attributed to J. Lages.

25 records · Page 2Linked to original sources
arXiv2003

Quasiparticle density of states of d-wave superconductors in a disordered vortex lattice

We calculate the density of states of a disordered inhomogeneous d-wave superconductor in a magnetic field. The field-induced vortices are assumed to be pinned at random positions and the effects of the scattering of the quasi-particles off the vortices are taken into account using the singular gauge transformation of Franz and Tesanovic. We find two regimes for the density of states: at very low energies the density of states follows a law ρ(ε) \sim ρ_0 + |ε|^α where the exponent is close to 1. A good fit of the density of states is obtained at higher energies, excluding a narrow region around the origin, with a similar power law energy dependence but with αclose to 2. Both at low and at higher energies ρ_0 scales with the inverse of the magnetic length (\sqrt{B}).

cond-mat.supr-con↗
arXiv2001

Restoration of Angular Lie Algebra Symmetries from a Covariant Hamiltonian

The sO(3) and the Lorentz algebra symmetries breaking with gauge curvatures are studied by means of a covariant Hamiltonian. The restoration of these algebra symmetries in flat and curved spaces is performed and led to the apparition of a monopole field. Then in the context of the Lorentz algebra we consider an application to the gravitoelectromagnetism theory. In this last case a qualitative relation giving a mass spectrum for dyons is established.

gr-qc↗
arXiv2001

Phase of bi-particle localized states for the Cooper problem in two-dimensional disordered systems

The Cooper problem is studied numerically for the Anderson model with disorder in two-dimensions. It is shown that the attractive Hubbard interaction creates a phase of bi-particle localized states in the regime where non-interacting states are delocalized. This phase cannot be obtained in the mean-field approximation and the pair coupling energy is strongly enhanced in this regime. The effects of magnetic field are studied and it is shown that under certain conditions they lead to delocalization.

cond-mat↗
arXiv2001

Disordered Hubbard Model with Attraction: Coupling Energy of Cooper Pairs in Small Clusters

We generalize the Cooper problem to the case of many interacting particles in the vicinity of the Fermi level in the presence of disorder. On the basis of this approach we study numerically the variation of the pair coupling energy in small clusters as a function of disorder. We show that the Cooper pair energy is strongly enhanced by disorder, which at the same time leads to the localization of pairs.

cond-mat↗
arXiv2000

Delocalization of two-particle ring near the Fermi level of 2d Anderson model

We study analytically and numerically the problem of two particles with a long range attractive interaction on a two-dimensional (2d) lattice with disorder. It is shown that below some critical disorder the interaction creates delocalized coupled states near the Fermi level. These states appear inside well localized noninteracting phase and have a form of two-particle ring which diffusively propagates over the lattice.

cond-mat↗
arXiv1999

Cooper problem in the vicinity of Anderson transition

We study numerically the ground state properties of the Cooper problem in the three-dimensional Anderson model. It is shown that attractive interaction creates localized pairs in the metallic noninteracting phase. This localization is destroyed at sufficiently weak disorder. The phase diagram for the delocalization transition in the presence of disorder and interaction is determined.

cond-mat↗