4,837 research outputs found
Coherent Magnetotransport Through an Artificial Molecule
The conductance in an extended multiband Hubbard model describing linear
arrays of up to ten quantum dots is calculated via a Lanczos technique. A
pronounced suppression of certain resonant conductance peaks in an applied
magnetic field due to a density-dependent spin-polarization transition is
predicted to be a clear signature of a coherent ``molecular'' wavefunction in
the array. A many-body enhancement of localization is predicted to give rise to
a {\em giant magnetoconductance} effect in systems with magnetic scattering.Comment: 4 pages, REVTEX 3.0, 5 figures included as postscript file
Gis Based Inventory of the Rivers of Northeastern Region of India For Their Conservation and Management
Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv
Density Matrix Renormalization Group Study of Incompressible Fractional Quantum Hall States
We develop the Density Matrix Renormalization Group (DMRG) technique for
numerically studying incompressible fractional quantum Hall (FQH) states on the
sphere. We calculate accurate estimates for ground state energies and
excitationgaps at FQH filling fractions \nu=1/3 and \nu=5/2 for systems that
are almost twice as large as the largest ever studied by exact diagonalization.
We establish, by carefully comparing with existing numerical results on smaller
systems, that DMRG is a highly effective numerical tool for studying
incompressible FQH states.Comment: 5 pages, 4 figure
Estimates of electronic interaction parameters for LaO compounds (=Ti-Ni) from ab-initio approaches
We have analyzed the ab-initio local density approximation band structure
calculations for the family of perovskite oxides, LaO with =Ti-Ni
within a parametrized nearest neighbor tight-binding model and extracted
various interaction strengths. We study the systematics in these interaction
parameters across the transition metal series and discuss the relevance of
these in a many-body description of these oxides. The results obtained here
compare well with estimates of these parameters obtained via analysis of
electron spectroscopic results in conjunction with the Anderson impurity model.
The dependence of the hopping interaction strength, t, is found to be
approximately .Comment: 18 pages; 1 tex file+9 postscript files (appeared in Phys Rev B Oct
15,1996
Phase diagram of asymmetric Fermi gas across Feshbach resonance
We study the phase diagram of the dilute two-component Fermi gas at zero
temperature as a function of the polarization and coupling strength. We map out
the detailed phase separations between superfluid and normal states near the
Feshbach resonance. We show that there are three different coexistence of
superfluid and normal phases corresponding to phase separated states between:
(I) the partially polarized superfluid and the fully polarized normal phases,
(II) the unpolarized superfluid and the fully polarized normal phases and (III)
the unpolarized superfluid and the partially polarized normal phases from
strong-coupling BEC side to weak-coupling BCS side. For pairing between two
species, we found this phase separation regime gets wider and moves toward the
BEC side for the majority species are heavier but shifts to BCS side and
becomes narrow if they are lighter.Comment: 4 pages, 3 figures. Submitted to LT25 on June 200
Dissipationless transport in low density bilayer systems
In a bilayer electronic system the layer index may be viewed as the
z-component of an isospin-1/2. An XY isospin-ordered ferromagnetic phase was
observed in quantum Hall systems and is predicted to exist at zero magnetic
field at low density. This phase is a superfluid for opposite currents in the
two layers. At B=0 the system is gapless but superfluidity is not destroyed by
weak disorder. In the quantum Hall case, weak disorder generates a random gauge
field which probably does not destroy superfluidity. Experimental signatures
include Coulomb drag and collective mode measurements.Comment: 4 pages, no figures, submitted to Phys. Rev. Let
Dynamic Magneto-Conductance Fluctuations and Oscillations in Mesoscopic Wires and Rings
Using a finite-frequency recursive Green's function technique, we calculate
the dynamic magneto-conductance fluctuations and oscillations in disordered
mesoscopic normal metal systems, incorporating inter-particle Coulomb
interactions within a self-consistent potential method. In a disordered metal
wire, we observe ergodic behavior in the dynamic conductance fluctuations. At
low , the real part of the conductance fluctuations is essentially
given by the dc universal conductance fluctuations while the imaginary part
increases linearly from zero, but for greater than the Thouless energy
and temperature, the fluctuations decrease as . Similar
frequency-dependent behavior is found for the Aharonov-Bohm oscillations in a
metal ring. However, the Al'tshuler-Aronov-Spivak oscillations, which
predominate at high temperatures or in rings with many channels, are strongly
suppressed at high frequencies, leading to interesting crossover effects in the
-dependence of the magneto-conductance oscillations.Comment: 4 pages, REVTeX 3.0, 5 figures(ps file available upon request),
#phd0
Smoothed Analysis of Dynamic Networks
We generalize the technique of smoothed analysis to distributed algorithms in
dynamic network models. Whereas standard smoothed analysis studies the impact
of small random perturbations of input values on algorithm performance metrics,
dynamic graph smoothed analysis studies the impact of random perturbations of
the underlying changing network graph topologies. Similar to the original
application of smoothed analysis, our goal is to study whether known strong
lower bounds in dynamic network models are robust or fragile: do they withstand
small (random) perturbations, or do such deviations push the graphs far enough
from a precise pathological instance to enable much better performance? Fragile
lower bounds are likely not relevant for real-world deployment, while robust
lower bounds represent a true difficulty caused by dynamic behavior. We apply
this technique to three standard dynamic network problems with known strong
worst-case lower bounds: random walks, flooding, and aggregation. We prove that
these bounds provide a spectrum of robustness when subjected to
smoothing---some are extremely fragile (random walks), some are moderately
fragile / robust (flooding), and some are extremely robust (aggregation).Comment: 20 page
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