4,509 research outputs found
Vortex matter and generalizations of dipolar superfluidity concept in layered systems
In the first part of this letter we discuss electrodynamics of an excitonic
condensate in a bilayer. We show that under certain conditions the system has a
dominant energy scale and is described by the effective electrodynamics with
"planar magnetic charges". In the second part of the paper we point out that a
vortex liquid state in bilayer superconductors also possesses dipolar
superfluid modes and establish equivalence mapping between this state and a
dipolar excitonic condensate. We point out that a vortex liquid state in an
N-layer superconductor possesses multiple topologically coupled dipolar
superfluid modes and therefore represents a generalization of the dipolar
superfluidity concept.Comment: v2: references added. v3: discussion extended, references adde
Locking and unlocking of the counterflow transport in nu=1 quantum Hall bilayers by tilting of magnetic field
The counterflow transport in quantum Hall bilayers provided by superfluid
excitons is locked at small input currents due to a complete leakage caused by
the interlayer tunneling. We show that the counterflow critical current
I_c^{CF} above which the system unlocks for the counterflow transport can be
controlled by a tilt of magnetic field in the plane perpendicular to the
current direction. The effect is asymmetric with respect to the tilting angle.
The unlocking is accompanied by switching of the systems from the d.c. to the
a.c. Josephson state. Similar switching takes place for the tunneling set-up
when the current flowing through the system exceeds the critical value I_c^T.
At zero tilt the relation between the tunnel and counterflow critical currents
is I_c^T=2 I_c^{CF}. We compare the influence of the in-plane magnetic field
component B_\parallel on the critical currents I_c^{CF} and I_c^T. The in-plane
magnetic field reduces the tunnel critical current and this reduction is
symmetric with respect to the tilting angle. It is shown that the difference
between I_c^{CF} and I_c^T is essential at field |B_\parallel|\lesssim \phi_0/d
\lambda_J, where \phi_0 is the flux quantum, d is the interlayer distance, and
\lambda_J is the Josephson length. At larger B_\parallel the critical currents
I_c^{CF} and I_c^T almost coincide each other.Comment: 10 pages, 1 fi
Charge ordering and interlayer phase coherence in quantum Hall superlattices
The possibility of the existence of states with a spontaneous interlayer
phase coherence in multilayer electron systems in a high perpendicular to the
layers magnetic field is investigated. It is shown that phase coherence can be
established in such systems only within individual pairs of adjacent layers,
while such coherence does not exist between layers of different pairs. The
conditions for stability of the state with interlayer phase coherence against
transition to a charge-ordered state are determined. It is shown that in the
system with the number of layers N\leq 10 these conditions are satisfied at any
value of the interlayer distance d. For N>10 there are two intervals of
stability: at sufficiently large and at sufficiently small d. For N\to \infty
the stability interval in the region of small d vanishesComment: 10 page
Phases of a bilayer Fermi gas
We investigate a two-species Fermi gas in which one species is confined in
two parallel layers and interacts with the other species in the
three-dimensional space by a tunable short-range interaction. Based on the
controlled weak coupling analysis and the exact three-body calculation, we show
that the system has a rich phase diagram in the plane of the effective
scattering length and the layer separation. Resulting phases include an
interlayer s-wave pairing, an intralayer p-wave pairing, a dimer Bose-Einstein
condensation, and a Fermi gas of stable Efimov-like trimers. Our system
provides a widely applicable scheme to induce long-range interlayer
correlations in ultracold atoms.Comment: 5 pages, 5 figures; (v2) stability of trimer is emphasized; (v3)
published versio
The QCD vacuum, confinement and strings in the Vacuum Correlator Method
In this review paper the QCD vacuum properties and the structure of color
fields in hadrons are studied using the complete set of gauge-invariant
correlators of gluon fields. Confinement in QCD is produced by the correlators
of some certain Lorentz structure, which violate abelian Bianchi identities and
therefore are absent in the case of QED. These correlators are used to define
an effective colorless field, which satisfies Maxwell equation with nonzero
effective magnetic current. With the help of the effective field and
correlators it is shown that quarks are confined due to effective magnetic
currents, squeezing gluonic fields into a string, in agreement with the ``dual
Meissner effect''. Distribution of effective gluonic fields are plotted in
mesons, baryons and glueballs with static sources.Comment: 36 pages, 19 figures, to appear in UFN, updated version. Few
references added, minor difference
Superfluidity of electron-hole pairs in randomly inhomogeneous bilayer systems
In bilayer systems electron-hole (e-h) pairs with spatially separated
components (i.e., with electrons in one layer and holes in the other) can be
condensed to a superfluid state when the temperature is lowered. This article
deals with the influence of randomly distributed inhomogeneities on the
superfluid properties of such bilayer systems in a strong perpendicular
magnetic field. Ionized impurities and roughenings of the conducting layers are
shown to decrease the superfluid current density of the e-h pairs. When the
interlayer distance is smaller than or close to the magnetic length, the
fluctuations of the interlayer distance considerably reduce the superfluid
transition temperature.Comment: 13 pages, 3 figure
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