13,704 research outputs found
Dynamical Casimir effect with cylindrical waveguides
I consider the quantum electromagnetic field in a coaxial cylindrical
waveguide, such that the outer cylindrical surface has a time-dependent radius.
The field propagates parallel to the axis, inside the annular region between
the two cylindrical surfaces. When the mechanical frequency and the thickness
of the annular region are small enough, only Transverse Electromagnetic (TEM)
photons may be generated by the dynamical Casimir effect. The photon emission
rate is calculated in this regime, and compared with the case of parallel
plates in the limit of very short distances between the two cylindrical
surfaces. The proximity force approximation holds for the transition matrix
elements in this limit, but the emission rate scales quadratically with the
mechanical frequency, as opposed to the cubic dependence for parallel plates.Comment: 6 page
Coulomb blockade in graphene nanoribbons
We propose that recent transport experiments revealing the existence of an
energy gap in graphene nanoribbons may be understood in terms of Coulomb
blockade. Electron interactions play a decisive role at the quantum dots which
form due to the presence of necks arising from the roughness of the graphene
edge. With the average transmission as the only fitting parameter, our theory
shows good agreement with the experimental data.Comment: 4 pages, 2 figure
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