1,337 research outputs found
Influence of the Intensity of Irradiation on the New Light-Effect in Chlorine Under Electrical Discharge
General conditions for the production of a new light-effect, viz., a photo-diminution of the conductivity in chlorine subjected to electrical discharge, arc indicated. The effect increases by Increasing the frequency of irradiation, the violet being most active, which happens to be the region of absorption by chlorine. In agreement with Joshi's views, who regards this phenomenon as distinct from a negative photo-electric effect, the influence of the light-intensity on the effect is not linear
Persistent currents in coupled mesoscopic rings
We have analysed the nature of persistent currents in open coupled mesoscopic
rings. Our system is comprised of two ideal loops connected to an electron
reservoir. We have obtained analytical expressions for the persistent current
densities in two rings in the presence of a magnetic field. We show that the
known even-odd parity effects in isolated single loops have to be generalised
for the case of coupled rings. We also show that when the two rings have
unequal circumferences, it is possible to observe opposite currents
(diamagnetic or paramagnetic) in the two rings for a given Fermi level.Comment: Submitted to PRB. 9 figures availabel on reques
Heat Capacity of Mesoscopic Superconducting Disks
We study the heat capacity of isolated giant vortex states, which are good
angular momentum () states, in a mesoscopic superconducting disk using the
Ginzburg-Landau (GL) theory. At small magnetic fields the =0 state
qualitatively behaves like the bulk sample characterized by a discontinuity in
heat capacity at . As the field is increased the discontinuity slowly
turns into a continuous change which is a finite size effect. The higher
states show a continuous change in heat capacity at at all fields. We
also show that for these higher states, the behavior of the peak position
with change in field is related to the paramagnetic Meissner effect
(irreversible) and can lead to an unambiguous observation of positive
magnetization in mesoscopic superconductors.Comment: Final versio
Vortex phase diagram for mesoscopic superconducting disks
Solving numerically the 3D non linear Ginzburg-Landau (GL) equations, we
study equilibrium and nonequilibrium phase transitions between different
superconducting states of mesoscopic disks which are thinner than the coherence
length and the penetration depth. We have found a smooth transition from a
multi-vortex superconducting state to a giant vortex state with increasing both
the disk thickness and the magnetic field. A vortex phase diagram is obtained
which shows, as function of the magnetic field, a re-entrant behavior between
the multi-vortex and the giant vortex state.Comment: 5 figures (post script files) include
Friedel phases and phases of transmission amplitudes in quantum scattering systems
We illustrate the relation between the scattering phase appearing in the
Friedel sum rule and the phase of the transmission amplitude for quantum
scatterers connected to two one-dimensional leads. Transmission zero points
cause abrupt phase changes of the phase of the transmission amplitude.
In contrast the Friedel phase is a continuous function of energy. We
investigate these scattering phases for simple scattering problems and
illustrate the behavior of these models by following the path of the
transmission amplitude in the complex plane as a function of energy. We verify
the Friedel sum rule for these models by direct calculation of the scattering
phases and by direct calculation of the density of states.Comment: 12 pages, 12 figure
Persistent Currents in the Presence of a Transport Current
We have considered a system of a metallic ring coupled to two electron
reservoirs. We show that in the presence of a transport current, the persistent
current can flow in a ring, even in the absence of magnetic field. This is
purely a quantum effect and is related to the current magnification in the
loop. These persistent currents can be observed if one tunes the Fermi energy
near the antiresonances of the total transmission coefficient or the two port
conductance.Comment: To appear in Phys. Rev. B. Three figures available on reques
Regular networks of Luttinger liquids
We consider arrays of Luttinger liquids, where each node is described by a
unitary scattering matrix. In the limit of small electron-electron interaction,
we study the evolution of these scattering matrices as the high-energy single
particle states are gradually integrated out. Interestingly, we obtain the same
renormalization group equations as those derived by Lal, Rao, and Sen, for a
system composed of a single node coupled to several semi-infinite 1D wires. The
main difference between the single node geometry and a regular lattice is that
in the latter case, the single particle spectrum is organized into periodic
energy bands, so that the renormalization procedure has to stop when the last
totally occupied band has been eliminated. We therefore predict a strongly
renormalized Luttinger liquid behavior for generic filling factors, which
should exhibit power-law suppression of the conductivity at low temperatures
E_{F}/(k_{F}a) >
1. Some fully insulating ground-states are expected only for a discrete set of
integer filling factors for the electronic system. A detailed discussion of the
scattering matrix flow and its implication for the low energy band structure is
given on the example of a square lattice.Comment: 16 pages, 7 figure
Hysteresis in mesoscopic superconducting disks: the Bean-Livingston barrier
The magnetization behavior of mesoscopic superconducting disks can show
hysteretic behavior which we explain by using the Ginzburg-Landau (GL) theory
and properly taking into account the de-magnetization effects due to
geometrical form factors. In large disks the Bean-Livingston surface barrier is
responsible for the hysteresis. While in small disks a volume barrier is
responsible for this hysteresis. It is shown that although the sample
magnetization is diamagnetic (negative), the measured magnetization can be
positive at certain fields as observed experimentally, which is a consequence
of the de-magnetization effects and the experimental set up.Comment: Latex file, 4 ps file
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