7,942 research outputs found
Transport and Coulomb drag for two interacting carbon nanotubes
We study nonlinear transport for two coupled one-dimensional quantum wires or
carbon nanotubes described by Luttinger liquid theory. Transport properties are
shown to crucially depend on the contact length . For a special
interaction strength, the problem can be solved analytically for arbitrary
. For point-like contacts and strong interactions, a qualitatively
different picture compared to a Fermi liquid emerges, characterized by
zero-bias anomalies and strong dependence on the applied cross voltage. In
addition, pronounced Coulomb drag phenomena are important for extended
contacts.Comment: 9 pages, 7 figures (eps files
Luttinger liquid behavior in single wall nanotubes
Transport properties of metallic single-wall nanotubes are examined based on
the Luttinger liquid theory. Focusing on a nanotube transistor setup, the
linear conductance is computed from the Kubo formula using perturbation theory
in the lead-tube tunnel conductances. For sufficiently long nanotubes and high
temperature, phonon backscattering should lead to an anomalous temperature
dependence of the resistivity.Comment: 5 pages, to appear in IWEPNM99 proceedings 1999, incl 2 figure
On the effects of irrelevant boundary scaling operators
We investigate consequences of adding irrelevant (or less relevant) boundary
operators to a (1+1)-dimensional field theory, using the Ising and the boundary
sine-Gordon model as examples. In the integrable case, irrelevant perturbations
are shown to multiply reflection matrices by CDD factors: the low-energy
behavior is not changed, while various high-energy behaviors are possible,
including ``roaming'' RG trajectories. In the non-integrable case, a Monte
Carlo study shows that the IR behavior is again generically unchanged, provided
scaling variables are appropriately renormalized.Comment: 4 Pages RevTeX, 3 figures (eps files
Impurity effects in few-electron quantum dots: Incipient Wigner molecule regime
Numerically exact path-integral Monte Carlo data are presented for
strongly interacting electrons confined in a 2D parabolic quantum dot,
including a defect to break rotational symmetry. Low densities are studied,
where an incipient Wigner molecule forms. A single impurity is found to cause
drastic effects: (1) The standard shell-filling sequence with magic numbers
, corresponding to peaks in the addition energy , is
destroyed, with a new peak at N=8, (2) spin gaps decrease,
(3) for N=8, sub-Hund's rule spin S=0 is induced, and (4) spatial ordering of
the electrons becomes rather sensitive to spin. We also comment on the recently
observed bunching phenomenon.Comment: 7 pages, 1 table, 4 figures, accepted for publication in Europhysics
Letter
Multilevel blocking Monte Carlo simulations for quantum dots
This article provides an introduction to the ideas behind the multilevel
blocking (MLB) approach to the fermion sign problem in path-integral Monte
Carlo simulations, and also gives a detailed discussion of MLB results for
quantum dots. MLB can turn the exponential severity of the sign problem into an
algebraic one, thereby enabling numerically exact studies of otherwise
inaccessible systems. Low-temperature simulation results for up to eight
strongly correlated electrons in a parabolic 2D quantum dot are presented.Comment: 10 Pages, includes 4 figures and mprocl.st
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