2,809 research outputs found
Massive liquid Ar and Xe detectors for direct Dark Matter searches
A novel experiment for direct searches of the Dark Matter with liquid argon
double-phase chamber with a mass of liquid Ar up to several hundred tons is
proposed. To suppress the b-, g- and n0- backgrounds, the comparison of
scintillation and ionization signals for every event is suggested. The addition
in liquid Ar of photosensitive Ge(CH3)4 or C2H4 and suppression of triplet
component of scintillation signals ensures the detection of scintillation
signals with high efficiency and provides a complete suppression of the
electron background. For the detection of photoelectrons and ionization
electrons, highly stable and reliable GEM detectors must be used.Comment: 8 pages, 2 figures, 1 tabl
Strong vortex-antivortex fluctuations in the type II superconducting film
The small size vortex-antivortex pairs proliferation in type II
superconducting film is considered for the wide interval of temperatures below
Tc. The corresponding contribution to free energy is calculated. It is shown
that these fluctuations give the main contribution to the heat capacity of the
film both at low temperatures and in the vicinity of transition
Static magneto-polarizability of cylindrical nanostructures
The static polarizability of cylindrical systems is shown to have a strong
dependence on a uniform magnetic field applied parallel to the tube axis. This
dependence is demonstrated by performing exact numerical diagonalizations of
simple cylinders (rolled square lattices), armchair and zig-zag carbon
nanotubes (rolled honeycomb lattices) for different electron-fillings. At low
temperature, the polarizability as function of the magnetic field has a
discontinuous character where plateau-like region are separated by sudden jumps
or peaks. A one to one correspondence is pointed out between each discontinuity
of the polarizability and the magnetic-field induced cross-over between the
ground state and the first excited state. Our results suggest the possibility
to use measurements of the static polarizability under magnetic field to get
important informations about excited states of cylindrical systems such as
carbon nanotubes.Comment: 9 eps fig
Mediatic graphs
Any medium can be represented as an isometric subgraph of the hypercube, with
each token of the medium represented by a particular equivalence class of arcs
of the subgraph. Such a representation, although useful, is not especially
revealing of the structure of a particular medium. We propose an axiomatic
definition of the concept of a `mediatic graph'. We prove that the graph of any
medium is a mediatic graph. We also show that, for any non-necessarily finite
set S, there exists a bijection from the collection M of all the media on a
given set S (of states) onto the collection G of all the mediatic graphs on S.Comment: Four axioms replaced by two; two references added; Fig.6 correcte
Spin crossover: the quantum phase transition induced by high pressure
The relationship is established between the Berry phase and spin crossover in
condensed matter physics induced by high pressure. It is shown that the
geometric phase has topological origin and can be considered as the order
parameter for such transition.Comment: 4 pages, 3 figure
Coupling angle resolved photoemission data and quasiparticle structure in antiferromagnetic insulators Sr2CuO2Cl2 and Ca2CuO2Cl2
We have analyzed the quasiparticle dispersion and ARPES-spectral density for
Sr2CuO2Cl2 and Ca2CuO2Cl2 antiferromagnetic insulators along basic symmetric
directions of the Brillouin zone (BZ) in a framework of an extended tight
binding method (ETBM) with explicit account for intracell strong electron
correlations. The quasiparticle dispersion is in a good agreement with ARPES-
data. At the top of valence band we found a narrow impurity-like virtual level
with the spectral weight proportional to the concentration of spin
fluctuations. A pseudogap between the virtual level and the top of the valence
band has dispersion similar to 'remnant Fermi surface' in Ca2CuO2Cl2 and to a
pseudogap in the underdoped Bi2212 samples. A calculated parity of the
polarized ARPES-spectra in (0,0),(pi/2,pi/2),(pi,0) - points in the AFM- phase
is even with regard to relative magnitudes of the partial contributions by
different orbitals to the total ARPES- spectral density. Conditions of an
observability for the different partial contributions in the polarized ARPES-
experiments are determined also.Comment: 15 pdf-pages with 10 figures and tabl
A new class of nodal stationary states in 2D Heisenberg ferromagnet
A new class of nodal topological excitations in a two-dimensional Heisenberg
model is studied. The solutions correspond to a nodal singular point of the
gradient field of the azimuthal angle. An analytical solution found for the
isotropic case. An effect of in-plane exchange anisotropy is studied
numerically. It results in solutions which are analogues of the conventional
out-of-plane solitons in the two-dimensional magnets.Comment: 5 figure
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