1,117 research outputs found
Nonequilibrium gas-liquid transition in the driven-dissipative photonic lattice
We study the nonequilibrium steady state of the driven-dissipative
Bose-Hubbard model with Kerr nonlinearity. Employing a mean-field decoupling
for the intercavity hopping , we find that the steep crossover between low
and high photon-density states inherited from the single cavity transforms into
a gasliquid bistability at large cavity-coupling . We formulate a van der
Waals like gasliquid phenomenology for this nonequilibrium situation and
determine the relevant phase diagrams, including a new type of diagram where a
lobe-shaped boundary separates smooth crossovers from sharp, hysteretic
transitions. Calculating quantum trajectories for a one-dimensional system, we
provide insights into the microscopic origin of the bistability.Comment: 5 pages, 4 figures + Supplemental Material (2 pages, 2 figures
Casimir Force between Vortex Matter in Anisotropic and Layered Superconductors
We present a new approach to calculate the attractive long range
vortex-vortex interaction of the van der Waals type present in anisotropic and
layered superconductors. The mapping of the statistical mechanics of vortex
lines onto the imaginary time quantum mechanics of two dimensional charged
bosons allows us to define a 2D Casimir problem: Two half-spaces of (dilute)
vortex matter separated by a gap of width R are mapped to two dielectric
half-planes of charged bosons interacting via a massive gauge field. We
determine the attractive Casimir force between the two half-planes and show,
that it agrees with the pairwise summation of the van der Waals force between
vortices previously found by Blatter and Geshkenbein [Phys. Rev. Lett. 77, 4958
(1996)]Comment: 11 pages, 3 figure
Characteristics of First-Order Vortex Lattice Melting: Jumps in Entropy and Magnetization
We derive expressions for the jumps in entropy and magnetization
characterizing the first-order melting transition of a flux line lattice. In
our analysis we account for the temperature dependence of the Landau parameters
and make use of the proper shape of the melting line as determined by the
relative importance of electromagnetic and Josephson interactions. The results
agree well with experiments on anisotropic YBaCuO and
layered BiSrCaCuO materials and reaffirm the validity of
the London model.Comment: 4 pages. We have restructured the paper to emphasize that in the
London scaling regime (appropriate for YBCO) our results are essentially
exact. We have also emphasized that a major controversy over the relevance of
the London model to describe VL melting has been settled by this wor
Non-equilibrium delocalization-localization transition of photons in circuit QED
We show that photons in two tunnel-coupled microwave resonators each
containing a single superconduct- ing qubit undergo a sharp non-equilibrium
delocalization-localization (self-trapping) transition due to strong
photon-qubit coupling. We find that dissipation favors the self-trapped regime
and leads to the possibility of observing the transition as a function of time
without tuning any parameter of the system. Furthermore, we find that
self-trapping of photons in one of the resonators (spatial localization) forces
the qubit in the opposite resonator to remain in its initial state (energetic
localization). This allows for an easy experimental observation of the
transition by local read-out of the qubit state.Comment: 4 pages, 5 figure
Structural lubricity: Role of dimension and symmetry
When two chemically passivated solids are brought into contact, interfacial
interactions between the solids compete with intrabulk elastic forces. The
relative importance of these interactions, which are length-scale dependent,
will be estimated using scaling arguments. If elastic interactions dominate on
all length scales, solids will move as essentially rigid objects. This would
imply superlow kinetic friction in UHV, provided wear was absent. The results
of the scaling study depend on the symmetry of the surfaces and the
dimensionalities of interface and solids. Some examples are discussed
explicitly such as contacts between disordered three-dimensional solids and
linear bearings realized from multiwall carbon nanotubes.Comment: 7 pages, 1 figur
Commensurate-incommensurate transition of cold atoms in an optical lattice
An atomic gas subject to a commensurate periodic potential generated by an
optical lattice undergoes a superfluid--Mott insulator transition. Confining a
strongly interacting gas to one dimension generates an instability where an
arbitrary weak potential is sufficient to pin the atoms into the Mott state;
here, we derive the corresponding phase diagram. The commensurate pinned state
may be detected via its finite excitation gap and the Bragg peaks in the static
structure factor.Comment: 4 pages, 2 figure
Edge Tunneling of Vortices in Superconducting Thin Films
We investigate the phenomenon of the decay of a supercurrent due to the
zero-temperature quantum tunneling of vortices from the edge in a thin
superconducting film in the absence of an external magnetic field. An explicit
formula is derived for the tunneling rate of vortices, which are subject to the
Magnus force induced by the supercurrent, through the Coulomb-like potential
barrier binding them to the film's edge. Our approach ensues from the
non-relativistic version of a Schwinger-type calculation for the decay of the
2D vacuum previously employed for describing vortex-antivortex pair-nucleation
in the bulk of the sample. In the dissipation-dominated limit, our explicit
edge-tunneling formula yields numerical estimates which are compared with those
obtained for bulk-nucleation to show that both mechanisms are possible for the
decay of a supercurrent.Comment: REVTeX file, 15 pages, 1 Postscript figure; to appear in Phys.Rev.
Mean-field glass transition in a model liquid
We investigate the liquid-glass phase transition in a system of point-like
particles interacting via a finite-range attractive potential in D-dimensional
space. The phase transition is driven by an `entropy crisis' where the
available phase space volume collapses dramatically at the transition. We
describe the general strategy underlying the first-principles replica
calculation for this type of transition; its application to our model system
then allows for an analytic description of the liquid-glass phase transition
within a mean-field approximation, provided the parameters are chosen suitably.
We find a transition exhibiting all the features associated with an `entropy
crisis', including the characteristic finite jump of the order parameter at the
transition while the free energy and its first derivative remain continuous.Comment: 12 pages, 6 figure
The influence of the Hall force on the vortex dynamics in type II superconductors
The effect of the Hall force on the pinning of vortices in type II
superconductors is considered. A field theoretic formulation of the pinning
problem allows a non-perturbative treatment of the influence of quenched
disorder. A self-consistent theory is constructed using the diagrammatic
functional method for the effective action, and an expression for the pinning
force for independent vortices as well as vortex lattices is obtained. We find
that the pinning force for a single vortex is suppressed by the Hall force at
low temperatures while it is increased at high temperatures. The effect of the
Hall force is more pronounced on a single vortex than on a vortex lattice. The
results of the self-consistent theory are shown to be in good agreement with
numerical simulations.Comment: 9 pages, 4 figures, published in Physical Review
Steric repulsion and van der Waals attraction between flux lines in disordered high Tc superconductors
We show that in anisotropic or layered superconductors impurities induce a
van der Waals attraction between flux lines. This attraction together with the
disorder induced repulsion may change the low B - low T phase diagram
significantly from that of the pure thermal case considered recently by Blatter
and Geshkenbein [Phys. Rev. Lett. 77, 4958 (1996)].Comment: Latex, 4 pages, 1 figure (Phys. Rev. Lett. 79, 139 (1997)
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