424 research outputs found
Collective charge density wave motion through an ensemble of Aharonov-Bohm rings
We investigate theoretically the collective charge density wave motion
through an ensemble of small disordered Aharonov-Bohm rings. It is shown that
the magnetic flux modulates the threshold field and the magnetoresistance with
a half flux quantum periodicity , resulting from ensemble
averaging over random scattering phases of multiple rings. The magnitude of the
magnetoresistance oscillations decreases rapidly with increasing bias. This is
consistent with recent experiments on in presence of columnar defects
[Phys. Rev. Lett. 78, 919 (1997)].Comment: 4 pages Revtex, 2 figures. Submitted to Phys. Rev. Let
A minimal approach for the local statistical properties of a one-dimensional disordered wire
We consider a one-dimensional wire in gaussian random potential. By treating
the spatial direction as imaginary time, we construct a `minimal'
zero-dimensional quantum system such that the local statistical properties of
the wire are given as products of statistically independent matrix elements of
the evolution operator of the system. The space of states of this quantum
system is found to be a particular non-unitary, infinite dimensional
representation of the pseudo-unitary group, U(1,1). We show that our
construction is minimal in a well defined sense, and compare it to the
supersymmetry and Berezinskii techniques.Comment: 10 pages, 0 figure
Quantum Interference of Coulomb Interaction and Disorder: Phase Shift of Friedel Oscillations and an Instability of the Fermi Sea
We investigate the influence of interference between Coulomb interaction and
impurity scattering on the static electronic response in
disordered metals to leading order in the effective Coulomb interaction. When
the transport relaxation time is much shorter than the
quasiparticle life time, we find a \mbox{sgn}(2p_F-q)/\sqrt{|2p_F-q|}
divergence of the polarization function at the Fermi surface (). It
causes a phase shift of the Friedel oscillations as well as an enhancement of
their amplitude. Our results are consistent with experiments and may be
relevant for understanding the stability of the amorphous state of certain
alloys against crystallization.Comment: 11 pages, 4 PostScript figures appended as a self-extracting tar
archive; includes output instruction
Anisotropic weakly localized transport in nitrogen-doped ultrananocrystalline diamond films
We establish the dominant effect of anisotropic weak localization (WL) in
three dimensions associated with a propagative Fermi surface, on the
conductivity correction in heavily nitrogen doped ultrananocrystalline diamond
(UNCD) films based on magneto-resistance studies at low temperatures. Also, low
temperature electrical conductivity can show weakly localized transport in 3D
combined with the effect of electron-electron interactions in these materials,
which is remarkably different from the conductivity in 2DWL or strong
localization regime. The corresponding dephasing time of electronic
wavefunctions in these systems described as ~ T^-p with p < 1, follows a
relatively weak temperature dependence compared to the generally expected
nature for bulk dirty metals having . The temperature dependence of
Hall (electron) mobility together with an enhanced electron density has been
used to interpret the unusual magneto-transport features and show delocalized
electronic transport in these n-type UNCD films, which can be described as
low-dimensional superlattice structures.Comment: 27 pages, 6 figures, To be published in Physical Review
Quantum-statistical equation-of-state models of dense plasmas: high-pressure Hugoniot shock adiabats
We present a detailed comparison of two self-consistent equation-of-state
models which differ from their electronic contribution: the atom in a spherical
cell and the atom in a jellium of charges. It is shown that both models are
well suited for the calculation of Hugoniot shock adiabats in the high pressure
range (1 Mbar-10 Gbar), and that the atom-in-a-jellium model provides a better
treatment of pressure ionization. Comparisons with experimental data are also
presented. Shell effects on shock adiabats are reviewed in the light of these
models. They lead to additional features not only in the variations of pressure
versus density, but also in the variations of shock velocity versus particle
velocity. Moreover, such effects are found to be responsible for enhancement of
the electronic specific heat.Comment: accepted in "Contributions to Plasma Physics" (2007
1D-Disordered Conductor with Loops Immersed in a Magnetic Field
We investigate the conductance of a 1-D disordered conducting loop with two
contacts, immersed in a magnetic flux. We show the appearance in this model of
the Al'tshuler-Aronov-Spivak behaviour. We also investigate the case of a chain
of loops distributed with finite density: in this case we show that the
interference effects due to the presence of the loops can lead to the
delocalization of the wave function.Comment: 8 pages; LaTeX; IFUM 463/FT; to appear in Phys. Lett.
Statistical Ensembles and Spectral Correlations in Mesoscopic Systems
Employing different statistical ensembles may lead to qualitatively different
results concerning averages of physical observables on the mesoscopic scale.
Here we discuss differences between the canonical and the grandcanonical
ensembles due to both quenched disorder and thermodynamical effects. We show
how these differences are related to spectral correlations of the system at
hand, and evaluate the conditions (temperature, system's size) when the
thermodynamic limit is achieved. We demonstrate our approach by evaluating the
heat capacity, persistent currents and the occupation probability of single
electron states, employing a systematic diagrammatic approach.Comment: 18 pages, Latex, 7 figures available by request, submitted to special
issue of "Chaos, Solitons & Fractals" on "Chaos and Quantum Transport in
Mesoscopic Cosmos
The Amplitude of Non-Equilibrium Quantum Interference in Metallic Mesoscopic Systems
We study the influence of a DC bias voltage V on quantum interference
corrections to the measured differential conductance in metallic mesoscopic
wires and rings. The amplitude of both universal conductance fluctuations (UCF)
and Aharonov-Bohm effect (ABE) is enhanced several times for voltages larger
than the Thouless energy. The enhancement persists even in the presence of
inelastic electron-electron scattering up to V ~ 1 mV. For larger voltages
electron-phonon collisions lead to the amplitude decaying as a power law for
the UCF and exponentially for the ABE. We obtain good agreement of the
experimental data with a model which takes into account the decrease of the
electron phase-coherence length due to electron-electron and electron-phonon
scattering.Comment: New title, refined analysis. 7 pages, 3 figures, to be published in
Europhysics Letter
Exact results for one-dimensional disordered bosons with strong repulsion
We study one-dimensional incommensurate bosons with strong repulsive
interactions and weak disorder. In analogy to the clean Tonks-Girardeau gas, a
Bose-Fermi mapping expresses this problem in terms of disordered free fermions.
Thereby many known results apply, in particular for the density-density
correlations, the distribution function of the local density of states, and the
complete spectral statistics. We also analyze the bosonic momentum
distribution, and comment on the experimental observability of these
predictions in ultracold atomic gases.Comment: 5 pages, 2 figures, published versio
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