5,521 research outputs found
Critical behavior of density of states near Fermi energy in low-dimensional disordered metals
We study the effect of electron-electron interaction on the one-particle
density of states (\emph{DOS}) of low-dimensional
disordered metals near Fermi energy within the framework of the finite
temperature conventional impurity diagram technique. We consider only diffusive
limit and by a geometric re-summation of the most singular first order
self-energy corrections via the Dyson equation we obtain a non-divergent
solution for the \emph{DOS} at low energies, while for higher energies the
well-known Altshuler-Aronov corrections are recovered. At the Fermi level
, this indicates that interacting disordered
two- and quasi-one-dimensional systems are in insulating state at zero
temperature. The obtained results are in good agreement with recent tunneling
experiments on two-dimensional GaAs/AlGaAs heterostructures and
quasi-one-dimensional doped multiwall carbon nanotubes.Comment: 8 pages, 4 figure
Renormalization of hole-hole interaction at decreasing Drude conductivity
The diffusion contribution of the hole-hole interaction to the conductivity
is analyzed in gated GaAs/InGaAs/GaAs heterostructures. We show
that the change of the interaction correction to the conductivity with the
decreasing Drude conductivity results both from the compensation of the singlet
and triplet channels and from the arising prefactor in the
conventional expression for the interaction correction.Comment: 6 pages, 5 figure
A model for the accidental catalysis of protein unfolding in vivo
Activated processes such as protein unfolding are highly sensitive to
heterogeneity in the environment. We study a highly simplified model of a
protein in a random heterogeneous environment, a model of the in vivo
environment. It is found that if the heterogeneity is sufficiently large the
total rate of the process is essentially a random variable; this may be the
cause of the species-to-species variability in the rate of prion protein
conversion found by Deleault et al. [Nature, 425 (2003) 717].Comment: 5 pages, 2 figure
Hole-hole interaction in a strained InGaAs two dimensional system
The interaction correction to the conductivity of 2D hole gas in strained
GaAs/InGaAs/GaAs quantum well structures was studied. It is shown
that the Zeeman splitting, spin relaxation and ballistic contribution should be
taking into account for reliable determination of the Fermi-liquid constant
. The proper consideration of these effects allows us to describe
both th temperature and magnetic field dependences of the conductivity and find
the value of .Comment: 7 pages, 6 figure
Diffusion and ballistic contributions of the interaction correction to the conductivity of a two-dimensional electron gas
The results of an experimental study of interaction quantum correction to the
conductivity of two-dimensional electron gas in AB semiconductor
quantum well heterostructures are presented for a wide range of
-parameter (), where is the transport
relaxation time. A comprehensive analysis of the magnetic field and temperature
dependences of the resistivity and the conductivity tensor components allows us
to separate the ballistic and diffusion parts of the correction. It is shown
that the ballistic part renormalizes in the main the electron mobility, whereas
the diffusion part contributes to the diagonal and does not to the off-diagonal
component of the conductivity tensor. We have experimentally found the values
of the Fermi-liquid parameters describing the electron-electron contribution to
the transport coefficients, which are found in a good agreement with the
theoretical results.Comment: 11 pages, 11 figure
Giant suppression of the Drude conductivity due to quantum interference in disordered two-dimensional systems
Temperature and magnetic field dependences of the conductivity in heavily
doped, strongly disordered two-dimensional quantum well structures
GaAs/InGaAs/GaAs are investigated within wide conductivity and
temperature ranges. Role of the interference in the electron transport is
studied in the regimes when the phase breaking length crosses over the
localization length with lowering temperature,
where and are the Fermi quasimomentum and mean free path,
respectively. It has been shown that all the experimental data can be
understood within framework of simple model of the conductivity over
delocalized states. This model differs from the conventional model of the weak
localization developed for and by one point: the
value of the quantum interference contribution to the conductivity is
restricted not only by the phase breaking length but by the
localization length as well. We show that just the quantity
rather than
, where is the dephasing time and
, is responsible for the temperature and
magnetic field dependences of the conductivity over the wide range of
temperature and disorder strength down to the conductivity of order .Comment: 11 pages, 15 figure
`Third' Quantization of Vacuum Einstein Gravity and Free Yang-Mills Theories
Based on the algebraico-categorical (:sheaf-theoretic and sheaf
cohomological) conceptual and technical machinery of Abstract Differential
Geometry, a new, genuinely background spacetime manifold independent, field
quantization scenario for vacuum Einstein gravity and free Yang-Mills theories
is introduced. The scheme is coined `third quantization' and, although it
formally appears to follow a canonical route, it is fully covariant, because it
is an expressly functorial `procedure'. Various current and future Quantum
Gravity research issues are discussed under the light of 3rd-quantization. A
postscript gives a brief account of this author's personal encounters with
Rafael Sorkin and his work.Comment: 43 pages; latest version contributed to a fest-volume celebrating
Rafael Sorkin's 60th birthday (Erratum: in earlier versions I had wrongly
written that the Editor for this volume is Daniele Oriti, with CUP as
publisher. I apologize for the mistake.
Local Moment Formation in the Superconducting State of a Doped Mott Insulator
A microscopic theory is presented for the local moment formation near a
non-magnetic impurity or a copper defect in high-T_c superconductors. We use a
renormalized meanfield theory of the t-J model for a doped Mott insulator and
study the fully self-consistent, spatially unrestricted solutions of the d-wave
superconducting (SC) state in both the spin S=0 and S=1/2 sectors. We find a
transition from the singlet d-wave SC state to a spin doublet SC state when the
renormalized exchange coupling exceeds a doping dependent critical value. The
induced S=1/2 moment is staggered and localized around the impurity. It arises
from the binding of an S=1/2 nodal quasiparticle excitation to the impurity.
The local density of states spectrum is calculated and connections to NMR and
STM experiments are discussed.Comment: 4 pages, 3 figures, revised version, to be published in Phys. Rev.
Let
Localized to extended states transition for two interacting particles in a two-dimensional random potential
We show by a numerical procedure that a short-range interaction induces
extended two-particle states in a two-dimensional random potential. Our
procedure treats the interaction as a perturbation and solve Dyson's equation
exactly in the subspace of doubly occupied sites. We consider long bars of
several widths and extract the macroscopic localization and correlation lengths
by an scaling analysis of the renormalized decay length of the bars. For ,
the critical disorder found is , and the critical
exponent . For two non-interacting particles we do not find any
transition and the localization length is roughly half the one-particle value,
as expected.Comment: 4 two-column pages, 4 eps figures, Revtex, to be published in
Europhys. Let
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