1,470 research outputs found
Temperature enhanced persistent currents and " periodicity"
We predict a non-monotonous temperature dependence of the persistent currents
in a ballistic ring coupled strongly to a stub in the grand canonical as well
as in the canonical case. We also show that such a non-monotonous temperature
dependence can naturally lead to a periodicity of the persistent
currents, where =h/e. There is a crossover temperature , below
which persistent currents increase in amplitude with temperature while they
decrease above this temperature. This is in contrast to persistent currents in
rings being monotonously affected by temperature. is parameter-dependent
but of the order of , where is the level spacing
of the isolated ring. For the grand-canonical case is half of that for
the canonical case.Comment: some typos correcte
Decentralized and stable matching in Peer-to-Peer energy trading
In peer-to-peer (P2P) energy trading, a secured infrastructure is required to
manage trade and record monetary transactions. A central server/authority can
be used for this. But there is a risk of central authority influencing the
energy price. So blockchain technology is being preferred as a secured
infrastructure in P2P trading. Blockchain provides a distributed repository
along with smart contracts for trade management. This reduces the influence of
central authority in trading. However, these blockchain-based systems still
rely on a central authority to pair/match sellers with consumers for trading
energy. The central authority can interfere with the matching process to profit
a selected set of users. Further, a centralized authority also charges for its
services, thereby increasing the cost of energy. We propose two distributed
mechanisms to match sellers with consumers. The first mechanism doesn't allow
for price negotiations between sellers and consumers, whereas the second does.
We also calculate the time complexity and the stability of the matching process
for both mechanisms. Using simulation, we compare the influence of centralized
control and energy prices between the proposed and the existing mechanisms. The
overall work strives to promote the free market and reduce energy prices
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
Delocalized-localized transition in a semiconductor two-dimensional honeycomb lattice
We report the magneto-transport properties of a two-dimensional electron gas
in a modulation-doped AlGaAs/GaAs heterostructure subjected to a lateral
potential with honeycomb geometry. Periodic oscillations of the
magneto-resistance and a delocalized-localized transition are shown by applying
a gate voltage. We argue that electrons in such artificial-graphene lattices
offer a promising approach for the simulation of quantum phases dictated by
Coulomb interactions
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
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
Probing the spin states of three interacting electrons in quantum dots
We observe a low-lying sharp spin mode of three interacting electrons in an
array of nanofabricated AlGaAs/GaAs quantum dots by means of resonant inelastic
light scattering. The finding is enabled by a suppression of the inhomogeneous
contribution to the excitation spectra obtained by reducing the number of
optically-probed quantum dots. Supported by configuration-interaction
calculations we argue that the observed spin mode offers a direct probe of
Stoner ferromagnetism in the simplest case of three interacting spin one-half
fermions
Paramagnetic Meissner effect in superconductors from self-consistent solutions of Ginzburg-Landau equations
The paramagnetic Meissner effect (PME) is observed in small superconducting
samples, and a number of controversial explanations of this effect are
proposed, but there is as yet no clear understanding of its nature. In the
present paper PME is considered on the base of the Ginzburg-Landau theory (GL).
The one-dimensional solutions are obtained in a model case of a long
superconducting cylinder for different cylinder radii R, the GL-parameters
\kappa and vorticities m. Acording to GL-theory, PME is caused by the presence
of vortices inside the sample. The superconducting current flows around the
vortex to screeen the vortex own field from the bulk of the sample. Another
current flows at the boundary to screen the external field H from entering the
sample. These screening currents flow in opposite directions and contribute
with opposite signs to the total magnetic moment (or magnetization) of the
sample. Depending on H, the total magnetization M may be either negative
(diamagnetism), or positive (paramagnetism). A very complicated saw-like
dependence M(H) (and other characteristics), which are obtained on the base of
self-consistent solutions of the GL-equations, are discussed.Comment: 6 pages, 5 figures, RevTex, submitted to Phys. Rev.
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