6,039 research outputs found
Influence of Cooper pairing on the inelastic processes in a gas of Fermi atoms
Correlation properties in ultracold Fermi gas with negative scattering length
and its impact on the three-body recombination is analyzed. We find that Cooper
pairing enhances the recombination rate in contrast to the decrease of this
rate accompanying Bose-Einstein condensation in a Bose gas. This trend is
characteristic for all interval of temperatures T<Tc
Formation of a condensed state with macroscopic number of phonons in ultracold Bose gases
A mechanism for the formation of a new type of stationary state with
macroscopical number of phonons in condensed atomic gases is proposed. This
mechanism is based on generating longitudinal phonons as a result of parametric
resonance caused by a permanent modulation of the transverse trap frequency in
an elongated trap. The phonon-phonon interaction predetermines the
self-consistent evolution which is completed with macroscopic population of one
from all levels within the energy interval of parametric amplification. This
level proves to be shifted to the edge of this interval. All other levels end
the evolution with zero population.Comment: 9 pages, 8 figure
Condensation of phonons in an ultracold Bose gas
We consider the generation of longitudinal phonons in an elongated
Bose-condensed gas at zero temperature due to parametric resonance as a result
of the modulation of the transverse trap frequency. The nonlinear temporal
evolution with account of the phonon-phonon interaction leads self-consistently
to the formation of the stationary state with the macroscopic occupation of a
single phonon quantum state.Comment: 5 pages, 1 figure, submitted to Phys.Rev.Letter
Modern trends in Superconductivity and Superfluidity. Chapters 11, 13
In Chapter 11 we present Fermi-gas approach for the search of s-wave and
p-wave superfluidity in three-dimensional solutions of He-3 in He-4 and in He-3
submonolayers. In Chapter 13 on the basis of the anisotropic and isotropic t-J
models we study spin-charge separation and confinement in ladder systems and in
high-Tc superconductors.Comment: In preparation for Springer-Verla
Manifestation of superfluidity in an evolving Bose-condensed gas
We study the generation of excitations due to an ''impurity''(static
perturbation) placed into an oscillating Bose-condensed gas in the
time-dependent trapping field. It is shown that there are two regions for the
position of the local perturbation. In the first region the condensate flows
around the ''impurity'' without generation of excitations demonstrating
superfluid properties. In the second region the creation of excitations occurs,
at least within a limited time interval, revealing destruction of
superfluidity. The phenomenon can be studied by measuring the damping of
condensate oscillations at different positions of the ''impurity''
Fermi-Bose mixtures and BCS-BEC crossover in high-Tc superconductors
In this review article we consider theoretically and give experimental
support to the models of the Fermi-Bose mixtures and the BCS-BEC crossover
compared with the strong-coupling approach, which can serve as the cornerstones
on the way from high-temperature to room-temperature superconductivity in
pressurized metallic hydrides. We discuss some key theoretical ideas and
mechanisms proposed for unconventional superconductors (cuprates, pnictides,
chalcogenides, bismuthates, diborides, heavy-fermions, organics, bilayer
graphene, twisted graphene, oxide hetero-structures), superfluids and balanced
or imbalanced ultracold Fermi gases in magnetic traps. We build a bridge
between unconventional superconductors and recently discovered pressurized
hydrides superconductors H3S and LaH10 with the critical temperature close to
room temperature. We discuss systems with line of nodal Dirac points close to
the Fermi surface, superconducting shape resonances and hyperbolic
superconducting networks which are very important for the development of novel
topological superconductors, for the energetics, for the applications in
nano-electronics and quantum computations.Comment: 19 pages, 7 figure
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