10,385 research outputs found
Cold Quark Matter, Quadratic Corrections and Gauge/String Duality
We make an estimate of the quadratic correction in the pressure of cold quark
matter using gauge/string duality.Comment: 7 pages; v.2: reference added; v.3: reference and comments added,
version to appear in PRD; v4. final version to appear in PRD; v.5: key
reference adde
Phase diagram of soft-core bosons in two dimensions
The low temperature phase diagram of Bose soft disks in two dimensions is
studied by numerical simulations. It is shown that a supersolid cluster phase
exists, within a range of the model parameters, analogous to that recently
observed for a system of aligned dipoles interacting via a softened potential
at short distance. These findings indicate that a long-range tail of the
interaction is unneeded to obtain such a phase, and that the soft-core
repulsive interaction is the minimal model for supersolidity
Self-consistent microscopic calculations for non-local transport through nanoscale superconductors
We implement self-consistent microscopic calculations in order to describe
out-of-equilibrium non-local transport in normal metal-superconductor-normal
metal hybrid structures in the presence of a magnetic field and for arbitrary
interface transparencies. A four terminal setup simulating usual experimental
situations is described by means of a tight-binding model. We present results
for the self-consistent order parameter and current profiles within the sample.
These profiles illustrate a crossover from a quasi-equilibrium to a strong
non-equilibrium situation when increasing the interface transparencies and the
applied voltages. We analyze in detail the behavior of the non-local
conductance in these two different regimes. While in quasi-equilibrium
conditions this can be expressed as the difference between elastic cotunneling
and crossed Andreev transmission coefficients, in a general situation
additional contributions due to the voltage dependence of the self-consistent
order parameter have to be taken into account. The present results provide a
first step towards a self-consistent theory of non-local transport including
non-equilibrium effects and describe qualitatively a recent experiment [Phys.
Rev. Lett. 97, 237003 (2006)].Comment: 12 pages, 14 figures, 2 figures correcte
Crossed Andreev reflection at spin-active interfaces
With the aid of the quasiclassical Eilenberger formalism we develop a theory
of non-local electron transport across three-terminal ballistic
normal-superconducting-normal (NSN) devices with spin-active NS interfaces. The
phenomenon of crossed Andreev reflection (CAR) is known to play the key role in
such transport. We demonstrate that CAR is highly sensitive to electron spins
and yields a rich variety of properties of non-local conductance which we
describe non-perturbatively at arbitrary voltages, temperature, spin-dependent
interface transmissions and their polarizations. Our results can be applied to
multi-terminal hybrid structures with normal, ferromagnetic and half-metallic
electrodes and can be directly tested in future experiments.Comment: 11 pages, 7 figures; figures 6 and 7 are corrected; version published
in Phys. Rev.
Nonlocal Andreev reflection at high transmissions
We analyze non-local effects in electron transport across three-terminal
normal-superconducting-normal (NSN) structures. Subgap electrons entering
S-electrode from one N-metal may form Cooper pairs with their counterparts
penetrating from another N-metal. This phenomenon of crossed Andreev reflection
-- combined with normal scattering at SN interfaces -- yields two different
contributions to non-local conductance which we evaluate non-perturbatively at
arbitrary interface transmissions. Both these contributions reach their maximum
values at fully transmitting interfaces and demonstrate interesting features
which can be tested in future experiments.Comment: 4 pages, 4 figure
Exotic Hybrid Quark Potentials
We use gauge/string duality to model some hybrid heavy-quark potentials. The
potentials under consideration can't be described by a single Nambu-Goto
string. This is why we call them "exotic". For , the result is in
quite good agreement with lattice simulations.Comment: 14 pages, 5 figures; v2: typos correcte
Two-photon correlations as a sign of sharp transition in quark-gluon plasma
The photon production arising due to time variation of the medium has been
considered. The Hamilton formalism for photons in time-variable medium (plasma)
has been developed with application to inclusive photon production. The results
have been used for calculation of the photon production in the course of
transition from quark-gluon phase to hadronic phase in relativistic heavy ion
collisions. The relative strength of the effect as well as specific two- photon
correlations have been evaluated. It has been demonstrated that the opposite
side two-photon correlations are indicative of the sharp transition from the
quark-gluon phase to hadrons.Comment: 23 pages, 2 figure
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