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

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

Phonon origin of high Tc in Superconducting cuprates

Eliashberg theory (ET) generalized for the account of the peculiar properties of the finite zone width electron-phonon (EP) systems with the non constant electron density of states, the electron-hole nonequivalence, chemical potential renormalization with doping and frequency, and electron correlations in the vertex function is used for the study of Tc in cuprates. The phonon contribution to the nodal anomalous electron Green function (GF) in cuprates is considered. The pairing on the full width of the electron zone was taken into account, not just on the Fermi surface. It is found that the finite zone width phenomenon in the newly derived Eliashberg equations for the finite zone width EP system together with the abrupt fall of the density of states above the Fermi surface are the crucial factors for the appearance of the high temperature superconductivity phenomenon. It is shown that near the optimal doping in the hole-doped cuprates high value is reproduced with the EP interaction constant obtained from tunnel experiments.Comment: 9 pages, 4 figure

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

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

BCS - BEC crossover and quantum hydrodynamics in p-wave superfluids with a symmetry of the A1 - phase

We solve the Leggett equations for the BCS - BEC crossover in the three dimension resonance p-wave superfluid with the symmetry of the A1 - phase. We calculate the sound velocity, the normal density, and the specific heat for the BCS-domain (\mu > 0), BEC-domain (\mu < 0), and close to important point \mu = 0 in 100% polarized case. We find the indications of quantum phase - transition close to the point \mu(T = 0) = 0. Deep in the BCS and BEC-domains the crossover ideas of Leggett and Nozieres, Schmitt-Rink work pretty well. We discuss the spectrum of orbital waves, the paradox of intrinsic angular momentum and complicated problem of chiral anomaly in the BCS A1 - phase at T = 0. We present two different approaches to a chiral anomaly: one based on supersymmetric hydrodynamics, another one on the formal analogy with the Dirac equation in quantum electrodynamics. We evaluate the damping of nodal fermions due to different decay processes in superclean case at T = 0 and find that we are in a ballistic regime \omega\tau >> 1. We propose to use aerogel or nonmagnetic impurities to reach hydrodynamic regime \omega\tau<< 1 at T = 0. We discuss the concept of the spectral flow and exact cancellations between time-derivatives of anomalous and quasiparticle currents in the equation for the total linear momentum conservation. We propose to derive and solve the kinetic equation for the nodal quasiparticles both in the hydrodynamic and in the ballistic regimes to demonstrate this cancellation explicitly. We briefly discuss the role of the other residual interactions different from damping and invite experimentalists to measure the spectrum and damping of orbital waves in A-phase of 3He at low temperatures.Comment: 14 pages, 10 figure