112 research outputs found
Charged complexes at the surface of liquid helium
Charged clusters in liquid helium in an external electric field form a
two-dimensional system below the helium surface. This 2D system undergoes a
phase transition from a liquid to a Wigner crystal at rather high temperatures.
Contrary to the electron Wigner crystal, the Wigner lattice of charged clusters
can be detected directly.Comment: 6 pages, 1 figur
Influence of magnetic impurities on the heat capacity of nuclear spins
It is found that in a wide range of temperatures and magnetic fields even a
small concentration of magnetic impurities in a sample leads to a
temperature dependence of the nuclear heat capacity. This effect is related to
a nuclear-spin polarization by the magnetic impurities. The parameter that
controls the theory turns out not to be the impurity concentration
but instead the quantity , where and are
the magnetic moments of an electron and a nucleus, respectively. The ratio of
and is of order of
Electron mobility on a surface of dielectric media: influence of surface level atoms
We calculate the contribution to the electron scattering rate from the
surface level atoms (SLA), proposed in [A.M. Dyugaev, P.D. Grigoriev, JETP
Lett. 78, 466 (2003)]. The inclusion of these states into account was
sufficient to explain the long-standing puzzles in the temperature dependence
of the surface tension of both He isotopes and to reach a very good agreement
between theory and experiment. We calculate the contribution from these SLA to
the surface electron scattering rate and explain some features in the
temperature dependence of the surface electron mobility. This contribution is
essential at low temperature when the He vapor concentration is
exponentially small. For an accurate calculation of the electron mobility one
also needs to consider the influence of the clamping electric field on the
surface electron wave function and the temperature dependence of the He3
chemical potential.Comment: 6 pages, 1 figur
Nuclear magnetic susceptibility of metals with magnetic impurities
We consider the contribution of magnetic impurities to the nuclear magnetic
susceptibility and to the specific heat of a metal. The impurity
contribution to the magnetic susceptibility has a behaviour, and the
impurity contribution to the specific heat has a behaviour, both in an
extended region of temperatures . In the case of a dirty metal the RKKY
interaction of nuclear spins and impurity spins is suppressed for low
temperatures and the main contribution to and is given by their
dipole-dipole interaction.Comment: 9 pages, 4 figures, REVTE
Fermi Liquid without Quasiparticles and Electron Spectral Functions of Two-Dimensional High- Superconductors
Properties of strongly correlated two-dimensional (2D) electron systems in
solids are studied on the assumption that these systems undergo a phase
transition, called fermion condensation, whose characteristic feature is
flattening of the electron spectrum \epsilon({\pf p}). Unlike the previous
models in the present study, the decay of single-particle states is properly
taken into account. Remarkably, the value of the topological charge ()
remains unchanged, supporting the view that systems with a fermion condensate
form a separate class of Fermi liquids. Results of calculations are found to be
in qualitative agreement with ARPES data.Comment: 13 pages, 3 figure
Thermodynamics of resonances and blurred particles
Exact and approximate expressions for thermodynamic characteristics of heated
matter, which consists of particles with finite mass-widths, are constructed.
They are expressed in terms of Fermi/Bose distributions and spectral functions,
rather than in terms of more complicated combinations between real and
imaginary parts of the self-energies of different particle species. Therefore
thermodynamically consistent approximate treatment of systems of particles with
finite mass-widths can be performed, provided spectral functions of particle
species are known. Approximation of the free resonance gas at low densities is
studied. Simple ansatz for the energy dependence of the spectral function is
suggested that allows to fulfill thermodynamical consistency conditions. On
examples it is shown that a simple description of dense systems of interacting
particle species can be constructed, provided some species can be treated in
the quasiparticle approximation and others as particles with widths. The
interaction affects quasiparticle contributions, whereas particles with widths
can be treated as free. Example is considered of a hot gas of heavy fermions
strongly interacting with light bosons, both species with zero chemical
potentials. The density of blurred fermions is dramatically increased for high
temperatures compared to the standard Boltzmann value. The system consists of
boson quasiparticles (with effective masses) interacting with fermion --
antifermion blurs. In thermodynamical values interaction terms partially
compensate each other. Thereby, in case of a very strong coupling between
species thermodynamical quantities of the system, like the energy, pressure and
entropy, prove to be such as for the quasi-ideal gas mixture of quasi-free
fermion blurs and quasi-free bosons.Comment: 35 page
Rearrangement of the Fermi Surface of Dense Neutron Matter and Direct Urca Cooling of Neutron Stars
It is proposed that a rearrangement of single-particle degrees of freedom may
occur in a portion of the quantum fluid interior of a neutron star. Such a
rearrangement is associated with the pronounced softening of the spin-isospin
collective mode which, under increasing density, leads to pion condensation.
Arguments and estimates based on fundamental relations of many-body theory show
that one realization of this phenomenon could produce very rapid cooling of the
star via a direct nucelon Urca process displaying a dependence on
temperature.Comment: 8 pages, 2 figure
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