6 research outputs found
Neutral weak currents in nucleon superfluid Fermi liquids: Larkin-Migdal and Leggett approaches
Neutrino emission in processes of breaking and formation of nucleon Cooper
pairs is calculated in the framework of the Larkin-Migdal and the Leggett
approaches to the description of superfluid Fermi liquids at finite
temperatures. We explain peculiarities of both approaches and explicitly
demonstrate that they lead to the same expression for the emissivity in pair
breaking and formation processes.Comment: 24 pages, 3 figure
London penetration depth in the tight binding approximation: Orthorhombic distortion and oxygen isotope effects in cuprates
We present a simple derivation of an expression for the superfluid density in superconductors with the tight binding energy
dispersion. The derived expression is discussed in detail because of its
distinction from the known expressions for ordinary superconductors with
parabolic energy dispersion. We apply this expression for the experimental data
analysis of the isotope effect in London penetration depth parameter in the BiSrCuO and YBaCuO family compounds near optimal doping, taking into
account the orthorhombic distortion of crystal structure, and estimate the
isotopic change of hopping parameters from the experimental data. We point out
that temperature behaviour is very sensitive to the ratio and estimate this quantity for a number of compounds.Comment: 10 pages, 4 figure
Neutrino emission due to Cooper-pair recombination in neutron stars revisited
Neutrino emission in processes of breaking and formation of neutron and
proton Cooper pairs is calculated within the Larkin-Migdal-Leggett approach for
a superfluid Fermi liquid. We demonstrate explicitly that the Fermi-liquid
renormalization respects the Ward identity and assures the weak vector current
conservation. The systematic expansion of the emissivities for small
temperatures and nucleon Fermi velocity, v_{F,i}, i=n,p, is performed. Both
neutron and proton processes are mainly controlled by the axial-vector current
contributions, which are not strongly changed in the superfluid matter. Thus,
compared to earlier calculations the total emissivity of processes on neutrons
paired in the 1S_0 state is suppressed by a factor ~(0.9-1.2) v_{F,n}^2. A
similar suppression factor (~v_{F,p}^2) arises for processes on protons.Comment: 12 pages, 1 figur