38 research outputs found
Breakdown of the Fermi Liquid picture in one dimensional fermion systems: connection with the energy level statistics
Using the adiabatic switching of interactions, we establish a condition for
the existence of electronic quasiparticles in a Luttinger liquid. It involves a
characteristic interaction strength proportional to the inverse square root of
the system length. An investigation of the exact energy level separation
probability distribution shows that this interaction scale also corresponds to
a cross-over from the non interacting behaviour to a rather typical case for
integrable systems, namely an exponential distribution. The level spacing
statistics of a spin , one branch Luttinger model are also analyzed, as
well as the level statistics of a two coupled chain model.Comment: 22 pages, Late
Localization Effect in a 2D Superconducting Network without Disorder
The superconducting properties of a two-dimensional superconducting wire
network with a new geometry have been measured as a function of the external
magnetic field. The extreme localization effect recently predicted for this
periodic lattice is revealed as a suppression of the critical current when the
applied magnetic field corresponds to half a flux quantum per unit cell. For
this particular magnetic field, the observed vortex state configuration is
highly disordered.Comment: 6 pages, 2 eps figures, submitted to Physica C. Title change
Interaction induced delocalisation for two particles in a periodic potential
We consider two interacting particles evolving in a one-dimensional periodic
structure embedded in a magnetic field. We show that the strong localization
induced by the magnetic field for particular values of the flux per unit cell
is destroyed as soon as the particles interact. We study the spectral and the
dynamical aspects of this transition.Comment: 4 pages, 5 EPS figures, minor misprints correcte
Coarsening on percolation clusters: out-of-equilibrium dynamics versus non linear response
We analyze the violations of linear fluctuation-dissipation theorem (FDT) in
the coarsening dynamics of the antiferromagnetic Ising model on percolation
clusters in two dimensions. The equilibrium magnetic response is shown to be
non linear for magnetic fields of the order of the inverse square root of the
number of sites. Two extreme regimes can be identified in the thermoremanent
magnetization: (i) linear response and out-of-equilibrium relaxation for small
waiting times (ii) non linear response and equilibrium relaxation for large
waiting times. The function characterizing the deviations from linear
FDT cross-overs from unity at short times to a finite positive value for longer
times, with the same qualitative behavior whatever the waiting time. We show
that the coarsening dynamics on percolation clusters exhibits stronger
long-term memory than usual euclidian coarsening.Comment: 17 pages, 10 figure
How to escape Aharonov-Bohm cages ?
We study the effect of disorder and interactions on a recently proposed
magnetic field induced localization mechanism. We show that both partially
destroy the extreme confinement of the excitations occuring in the pure case
and give rise to unusual behavior. We also point out the role of the edge
states that allows for a propagation of the electrons in these systems.Comment: 22 pages, 20 EPS figure
Glauber Dynamics and Ageing
The Glauber dynamics of various models (REM-like trap models, Brownian motion, BM model, Ising chain and SK model) is analyzed in relation with the existence of ageing. From a finite size Glauber matrix, we calculate a time after which the system has relaxed to the equilibrium state. The case of metastability is also discussed. If the only non zero overlaps between pure states are only self-overlaps (REM-like trap models, BM model), the existence or absence of ageing depends only on the behavior of the density of eigenvalues for small eigenvalues. We have carried out a detailed numerical and analytical analysis of the density of eigenvalues of the REM-like trap models. In this case, we show that the behavior of the density of eigenvalues for typical trap realizations is related to the spectral dimension of the equivalent random walk model
Vortex correlations in a fully frustrated two-dimensional superconducting network
7 pages, 6 figuresWe have investigated the vortex state in a superconducting dice network using the Bitter decoration technique at several magnetic frustrations f=1/2 and 1/3. In contrast to other regular network geometries where the existence of a commensurate state was previouly demonstrated, no ordered state was observed in the dice network at f=1/2 and the observed vortex-vortex correlation length is close to one lattice cell
Vortex correlations in a fully frustrated two-dimensional superconducting network
We have investigated the vortex state in a superconducting dice
network using the Bitter decoration technique at several magnetic
frustrations and 1/3. In contrast to
other regular network geometries where the existence of a commensurate
state was previouly demonstrated, no ordered state was observed in
the dice network at f=1/2 and the observed vortex-vortex correlation
length is close to one lattice cell