7,508 research outputs found
Weak Localization Thickness Measurements of Si:P Delta-Layers
We report on our results for the characterization of Si:P delta-layers grown
by low temperature molecular beam epitaxy. Our data shows that the effective
thickness of a delta-layer can be obtained through a weak localization analysis
of electrical transport measurements performed in perpendicular and parallel
magnetic fields. An estimate of the diffusivity of phosphorous in silicon is
obtained by applying this method to several samples annealed at 850 Celsius for
intervals of zero to 15 minutes. With further refinements, this may prove to be
the most precise method of measuring delta-layer widths developed to date,
including that of Secondary Ion Mass Spectrometry analysis
Non-Minimal and Non-Universal Supersymmetry
I motivate and discuss non-minimal and non-universal models of supersymmetry
and supergravity consistent with string unification at GeV.Comment: 10 pages, Latex. Plenary talk given at 6th Workshop in High Energy
Physics Phenomenology (WHEPP 6), Chennai (Madras), India, 3-15 Jan 200
Andreev current in finite sized carbon nanotubes
We investigate the effect of interactions on Andreev current at a
normal-superconducting junction when the normal phase is a Luttinger liquid
with repulsive interactions. In particular, we study the system of a finite
sized carbon nanotube placed between one metallic and one superconducting lead.
We show that interactions and finite size effects give rise to significant
deviations from the standard picture of Andreev current at a normal-
superconductor junction in the nearly perfect Andreev limit.Comment: 4 pages, 2 figure
Time correlations in 1D quantum impurity problems
We develop in this letter an analytical approach using form- factors to
compute time dependent correlations in integrable quantum impurity problems. As
an example, we obtain for the first time the frequency dependent conductivity
for the tunneling between the edges in the fractional
quantum Hall effect, and the spectrum of the spin-spin correlation in
the anisotropic Kondo model and equivalently in the double well system of
dissipative quantum mechanics, both at vanishing temperature.Comment: 4 pages, Revtex and 2 figure
Hyperelliptic curves for multi-channel quantum wires and the multi-channel Kondo problem
We study the current in a multi-channel quantum wire and the magnetization in
the multi-channel Kondo problem. We show that at zero temperature they can be
written simply in terms of contour integrals over a (two-dimensional)
hyperelliptic curve. This allows one to easily demonstrate the existence of
weak-coupling to strong-coupling dualities. In the Kondo problem, the curve is
the same for under- and over-screened cases; the only change is in the contour.Comment: 7 pages, 1 figure, revte
Quasi-particles in Fractional Quantum Hall Effect Edge Theories
We propose a quasi-particle formulation of effective edge theories for the
fractional quantum Hall effect. For the edge of a Laughlin state with filling
fraction \nu=1/m, our fundamental quasi-particles are edge electrons of charge
-e and edge quasi-holes of charge +e/m. These quasi-particles satisfy exclusion
statistics in the sense of Haldane. We exploit algebraic properties of edge
electrons to derive a kinetic equation for charge transport between a \nu=1/m
fractional quantum Hall edge and a normal metal. We also analyze alternative
`Boltzmann' equations that are directly based on the exclusion statistics
properties of edge quasi-particles. Generalizations to more general filling
fractions (Jain series) are briefly discussed.Comment: 20 pages, 2 eps figures, revtex, references updated, Phys. Rev. B in
pres
Non-equilibrium DC noise in a Luttinger liquid with impurity
We compute exactly the non-equilibrium DC noise in a Luttinger liquid with an
impurity and an applied voltage. By generalizing Landauer transport theory for
Fermi liquids to interacting, integrable systems, we relate this noise to the
density fluctuations of quasiparticles. We then show how to compute these
fluctuations using the Bethe ansatz. The non-trivial density correlations from
the interactions result in a substantial part of the non-equilibrium noise. The
final result for the noise is a scaling function of the voltage, temperature
and impurity coupling. It may eventually be observable in tunneling between
edges of a fractional quantum Hall effect device.Comment: 10 pages with one figure, uses revtex and eps
Production of pseudoscalar Higgs-bosons in collisions
We investigate the production of a pseudoscalar Higgs-boson using the
reaction at an collider with center of
mass energy of 500 GeV. Supersymmetric contributions are included and provide a
substantial enhancement to the cross section for most values of the symmetry
breaking parameters. We find that, despite the penalty incurred in converting
one of the beams into a source of backscattered photons, the
process is a promising channel for the detection of the .Comment: 9 pages RevTex + 2 Postscript figures tar.gzip.uuencode
Single Top Quark Production as a Probe for Anomalous Moments at Hadron Colliders
Single production of top quarks at hadron colliders via fusion is
examined as a probe of possible anomalous chromomagnetic and/or chromoelectric
moment type couplings between the top and gluons. We find that this channel is
far less sensitive to the existence of anomalous couplings of this kind than is
the usual production of top pairs by or fusion. This result is
found to hold at both the Tevatron as well as the LHC although somewhat greater
sensitivity for anomalous couplings in this channel is found at the higher
energy machine.Comment: New discussion and 10 new figures added. uuencoded postscript fil
Finite Size Analysis of Luttinger Liquids with a source of 2k_f Scattering
Numerical analysis of the spectrum of large finite size Luttinger liquids
(g<1) in the presence of a single source of 2k_f scattering has been made
possible thanks to an effective integration of high degrees of freedom.
Presence of irrelevant operators and their manifestation in transport are
issues treated independently. We confirm the existence of two irrelevant
operators: particle hopping and charge oscillations, with regions of dominance
separated by g=1/2. Temperature dependence of conductance is shown to be
dominated by hopping alone. Frequency dependence is affected by both irrelevant
operators.Comment: 4 pages, LaTex (RevTex), 3 PostScript figures appende
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