46 research outputs found
--Oscillations for Correlated Electron Pairs in Disordered Mesoscopic Rings
The full spectrum of two interacting electrons in a disordered mesoscopic
one--dimensional ring threaded by a magnetic flux is calculated numerically.
For ring sizes far exceeding the one--particle localization length we
find several --periodic states whose eigenfunctions exhibit a pairing
effect. This represents the first direct observation of interaction--assisted
coherent pair propagation, the pair being delocalized on the scale of the whole
ring.Comment: 4 pages, uuencoded PostScript, containing 5 figures
Mesoscopic Luttinger Liquid Theory in an Aharonov-Bohm Ring
A careful study on the mesoscopic PC in a Luttinger liquid ring is carried
out.
It is shown that discreteness plays an important role in calculating the PC
caused by the magnetic flux. At zero temperature, the current is shown to be
independent of the interaction even when is not zero. The current
becomes enhanced at finite temperatures comparing to the non-interacting case,
when the parameter g is positive.Comment: 4 pages, 2 figures. Version to appear in PR
Spin and interaction effects on charge distribution and currents in one-dimensional conductors and rings within the Hartree-Fock approximation
Using the self--consistent Hartree-Fock approximation for electrons with spin
at zero temperature, we study the effect of the electronic interactions on the
charge distribution in a one-dimensional continuous ring containing a single
scatterer. We reestablish that the interaction suppresses the decay
of the Friedel oscillations. Based on this result, we show that in an infinite
one dimensional conductor containing a weak scatterer, the current is totally
suppressed because of a gap opened at the Fermi energy. In a canonical ensemble
of continuous rings containing many scatterers, the interactions enhance the
average and the typical persistent current.Comment: 5 pages, 4 figure
Analytical Results for Random Band Matrices with Preferential Basis
Using the supersymmetry method we analytically calculate the local density of
states, the localiztion length, the generalized inverse participation ratios,
and the distribution function of eigenvector components for the superposition
of a random band matrix with a strongly fluctuating diagonal matrix. In this
way we extend previously known results for ordinary band matrices to the class
of random band matrices with preferential basis. Our analytical results are in
good agreement with (but more general than) recent numerical findings by
Jacquod and Shepelyansky.Comment: 8 pages RevTex and 1 Figure, both uuencode
Conductance length autocorrelation in quasi one-dimensional disordered wires
Employing techniques recently developed in the context of the Fokker--Planck
approach to electron transport in disordered systems we calculate the
conductance length correlation function
for quasi 1d wires. Our result is valid for arbitrary lengths L and .
In the metallic limit the correlation function is given by a squared
Lorentzian. In the localized regime it decays exponentially in both L and
. The correlation length is proportional to L in the metallic regime
and saturates at a value approximately given by the localization length
as .Comment: 23 pages, Revtex, two figure
Persistent currents in two dimensions: New regimes induced by the interplay between electronic correlations and disorder
Using the persistent current I induced by an Aharonov-Bohm flux in square
lattices with random potentials, we study the interplay between electronic
correlations and disorder upon the ground state (GS) of a few polarized
electrons (spinless fermions) with Coulomb repulsion. K being the total
momentum, we show that I is proportional to K in the continuum limit. We use
this relation to distinguish between the continuum regimes, where the lattice
GS behaves as in the continuum limit and I is independent of the interaction
strength U when K is conserved, and the lattice regimes where I decays as U
increases. Changing the disorder strength W and U, we obtain many regimes which
we study using the map of local currents carried by three spinless fermions
Does the attractive Hubbard model support larger persistent currents than the repulsive one ?
We consider a one-dimensional Hubbard model in the presence of disorder. We
compute the charge stiffness for a mesoscopic ring, as a function of the size
, which is a measure of the permanent currents. We find that for finite
disorder the permanent currents of the system with repulsive interactions are
larger than those of the system with attractive interactions. This counter
intuitive result is due to the fact that local density fluctuations are reduced
in the presence of repulsive interactions.Comment: 14 pages; Revtex 3.0; 3 postscript figures uuencoded with uufile
Persistent Currents in 1D Disordered Rings of Interacting Electrons
We calculate the persistent current of 1D rings of spinless fermions with
short-range interactions on a lattice with up to 20 sites, and in the presence
of disorder, for various band fillings. We find that {\it both} disorder and
interactions always decrease the persistent current by localizing the
electrons. Away from half-filling, the interaction has a much stronger
influence in the presence of disorder than in the pure case.Comment: Latex file, 11 pages, 5 figures available on request, Report
LPQTH-93/1
Electron-electron interactions in one- and three-dimensional mesoscopic disordered rings: a perturbative approach
We have computed persistent currents in a disordered mesoscopic ring in the
presence of small electron-electron interactions, treated in first order
perturbation theory. We have investigated both a contact (Hubbard) and a
nearest neighbour interaction in 1D and 3D. Our results show that a repulsive
Hubbard interaction produces a paramagnetic contribution to the average current
(whatever the dimension) and increases the value of the typical current. On the
other hand, a nearest neighbour repulsive interaction results in a diamagnetic
contribution in 1D and paramagnetic one in 3D, and tends to decrease the value
of the typical current in any dimension. Our study is based on numerical
simulations on the Anderson model and is justified analytically in the presence
of very weak disorder. We have also investigated the influence of the amount of
disorder and of the statistical (canonical or grand-canonical) ensemble.Comment: 7 pages in REVTEX, 4 figure
The interplay between electron-electron interactions and impurities in one-dimensional rings
The persistent current and charge stiffness of a one-dimensional Luttinger
liquid on a ring threaded by a magnetic flux are calculated by Monte Carlo
simulation. By changing the random impurity potential strength and the
electron-electron interaction, we see a crossover behavior between weak and
strong impurity limits. For weak impurity potentials, interactions enhance
impurity effects, that is, interactions decrease the current and the stiffness.
On the other hand, interactions tend to screen impurities when the impurity
potential is strong. Temperature dependence of the persistent current and the
charge stiffness shows a peak at a characteristic temperature, consistent with
a recent single impurity study.Comment: 4 pages (ReVTeX3.0) + 3 figures (in uuencoded postscript format)
appended in the end of the fil