Condensed Matter
We study the effects of non-magnetic impurity vertex correction on nuclear spin-lattice relaxation rate $1/{T_1} $ of conventional s-wave superconductors within the Eliashberg formalism. We obtain, with a self-consistent $t-$matrix…
A numerical approach to ground-state dynamical correlation functions from Density Matrix Renormalization Group (DMRG) is developed. Using sum rules, moments of a dynamic correlation function can be calculated with DMRG, and with the moments…
We use our recently developed functional bosonization approach to bosonize interacting fermions in arbitrary dimension $d$ beyond the Gaussian approximation. Even in $d=1$ the finite curvature of the energy dispersion at the Fermi surface…
We bosonize the long-wavelength excitations of interacting fermions in arbitrary dimension by directly applying a suitable Hubbard-Stratonowich transformation to the Grassmannian generating functional of the fermionic correlation functions.…
The systematics of the size dependence of the resonant response of small metal particles and nuclei to incident electromagnetic radiation is studied. The known radius$^{-1}$ variation of the full width at half maximum (FWHM) in…
Inspired by the recent experiments on Y$_{2-x}$Ca$_x$BaNiO$_5$, (J. F. DiTusa {\it et al.}, Phys. Rev. Lett. 73, 1857 (1994)), we discuss the dispersion relation of the $s$=1/2 particles in the $s$=1 Heisenberg and VBS model in the limit of…
We consider the supercurrent flow through gated mesoscopic semiconductor hetrostructures in which a two-dimensional normal constriction is confined between superconducting electrodes. We show that for these structures the Josephson current,…
Recent angle resolved photoemission (ARPES) results for the insulating cuprate ${\rm Sr_2 Cu O_2 Cl_2}$ have provided the first experimental data which can be directly compared to the (theoretically) well--studied problem of a single hole…
We study models of chiral interacting fermions by means of conformal and Bethe-Ansatz techniques, and determine their thermodynamic properties and asymptotic correlation functions. We identify a class of fixed points characterizing the…
We study the Toulouse limit of the multi-channel Kondo model defined as the limit of maximal anisotropy which can be achieved without changing the infrared behaviour of the model. It is shown that when the number of channels exceeds 2, the…
In this paper, we study the physics of mesoscopic systems with noninteracting, but fixed number of electrons. From a technical point of view, this means a discussion of the differences between the canonical and the grand canonical ensemble…
We propose an information-theoretic statistical model to describe the universal features of those chaotic scattering processes characterized by a prompt and an equilibrated component. The model, introduced in the past in nuclear physics,…
We present a general theory for the equilibrium current distribution in an interacting two-dimensional electron gas subjected to a perpendicular magnetic field, and confined by a potential that varies slowly on the scale of the magnetic…
We present a detailed analysis for the Langevin dynamics of a spherical spin-glass model (the spherical Sherrington-Kirkpatrick model). All the spins in the system are coupled by pairs via a random interaction matrix taken from the Gaussian…
Numerical calculations of the kinetic energy of various extensions of the one-dimensional Hubbard model including dimerization and repulsion between nearest neighbours are reported. Using the sum rule that relates the kinetic energy to the…
We show that the zero temperature susceptibility of the one-dimensional, dimerized Hubbard model at quarter-filling can be accurately determined on the basis of exact diagonalization of small clusters. The best procedure is to perform a…
The Kubo formula for the conductance of classically chaotic systems is analyzed semiclassically, yielding simple expressions for the mean and the variance of the quantum interference terms. In contrast to earlier work, here times longer…
A global analysis of the scaling behaviour of a system with a scalar order parameter quenched to zero temperature is obtained by numerical simulation of the Ginzburg-Landau equation with conserved and non conserved order parameter. A rich…
We study the statistical mechanics of a $D$-dimensional array of Josephson junctions in presence of a magnetic field on a lattice of side $2$. In the high temperature region the thermodynamical properties can be computed in the limit $D \to…
The interaction of an edge dislocation made of half the superconducting plane with a magnetic interlayer vortex is considered within the framework of the Lawrence-Doniach model with negative as well as positive Josephson interlayer…