9,100 research outputs found
Born-form approximation for e+ e- to W+ W- to 4 fermions(+gamma)
We review the results on representing the differential cross section for
W-pair production, including W decay and hard-photon bremsstrahlung, in terms
of a Born-form approximation of fairly simple analytic form.Comment: 16 pages with 3 figures,(eps files), Latex. Invited talk at the XXII
International School of Theoretical Physics, Ustron '99, Poland, September
199
Joule heating induced negative differential resistance in free standing metallic carbon nanotubes
The features of the characteristics of metallic carbon nanotubes (m-NTs)
in different experimental setups are studied using semi-classical Boltzmann
transport equation together with the heat dissipation equation to account for
significant thermal effects at high electric bias. Our model predicts that the
shape of the m-NT characteristics is basically controlled by heat removal
mechanisms. In particular we show that the onset of negative differential
resistance in free standing nanotubes finds its origins in strong transport
nonlinearities associated with poor heat removal unlike in substrate-supported
nanotubes.Comment: 3 pages, 3 figure
Surface Shubnikov-de Hass oscillations and non-zero Berry phases of the topological hole conduction in TlBiSe
We report the observation of two-dimensional Shubnikov-de Hass (SdH)
oscillations in the topological insulator TlBiSe. Hall
effect measurements exhibited electron-hole inversion in samples with bulk
insulating properties. The SdH oscillations accompanying the hole conduction
yielded a large surface carrier density of /cm, with the Landau-level fan diagram exhibiting the
Berry phase. These results showed the electron-hole reversibility around the
in-gap Dirac point and the hole conduction on the surface Dirac cone without
involving the bulk metallic conduction.Comment: 5 pages, 4 figure
High field electro-thermal transport in metallic carbon nanotubes
We describe the electro-thermal transport in metallic carbon nanotubes
(m-CNTs) by a semi-classical approach that takes into account the high-field
dynamical interdependence between charge carrier and phonon populations. Our
model is based on the self-consistent solution of the Boltzmann transport
equation and the heat equation mediated by a phonon rate equation that accounts
for the onset of non-equilibrium (optical) phonons in the high-field regime.
Given the metallic nature of the nanostructures, a key ingredient of the model
is the assumption of local thermalization of charge carriers. Our theory
remarkably reproduces the room temperature electrical characteristics of m-CNTs
on substrate and free standing (suspended), shedding light on charge-heat
transport in these one dimensional nanostructures. In particular, the negative
differential resistance observed in suspended m-CNTs under electric stress is
attributed to inhomogeneous field profile induced by self-heating rather than
the presence of hot phonons.Comment: 10 pages, 10 figure
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