6,123 research outputs found
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
Relaxation of superflow in a network: an application to the dislocation model of supersolidity of helium crystals
We have considered the dislocation network model for the supersolid state in
He-4 crystals. In difference with uniform 2D and 3D systems, the temperature of
superfluid transition T_c in the network is much smaller than the degeneracy
temperature T_d. It is shown that a crossover into a quasi superfluid state
occurs in the temperature interval between T_c and T_d. Below the crossover
temperature the time of decay of the flow increases exponentially under
decrease of the temperature. The crossover has a continuous character and the
crossover temperature does not depend on the density of dislocations.Comment: Corrected typo
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
Quenched Dislocation Enhanced Supersolid Ordering
I show using Landau theory that quenched dislocations can facilitate the
supersolid (SS) to normal solid (NS) transition, making it possible for the
transition to occur even if it does not in a dislocation-free crystal. I make
detailed predictions for the dependence of the SS to NS transition temperature
T_c(L), superfluid density %\rho_S(T, L), and specific heat C(T,L) on
temperature T and dislocation spacing L, all of which can be tested against
experiments. The results should also be applicable to an enormous variety of
other systems, including, e.g., ferromagnets.Comment: 5 pages, 2 figure
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
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