7,651 research outputs found
Quantum spin metal state on a decorated honeycomb lattice
We present a modification of exactly solvable spin-(1/2) Kitaev model on the
decorated honeycomb lattice, with a ground state of "spin metal" type. The
model is diagonalized in terms of Majorana fermions; the latter form a 2D
gapless state with a Fermi-circle those size depends on the ratio of exchange
couplings. Low-temperature heat capacity C(T) and dynamic spin susceptibility
\chi(\omega,T) are calculated in the case of small Fermi-circle. Whereas
C(T)\sim T at low temperatures as it is expected for a Fermi-liquid, spin
excitations are gapful and \chi(\omega,T) demonstrate unusual behaviour with a
power-law peak near the resonance frequency. The corresponding exponent as well
as the peak shape are calculated.Comment: 4 pages, 3 figure
Charge-exchange resonances and restoration of the Wigner SU(4)-symmetry in heavy and superheavy nuclei
Energies of the giant Gamow-Teller and analog resonances - and
, are presented, calculated using the microscopic theory of finite
Fermi system. The calculated differences go to zero in heavier nuclei indicating the restoration of Wigner
SU(4)-symmetry. The calculated values are in good
agreement with the experimental data. The average deviation is 0.30 MeV for the
33 considered nuclei for which experimental data is available. The values were calculated for heavy and superheavy nuclei up to the
mass number = 290. Using the experimental data for the analog resonances
energies, the isotopic dependence of the difference of the Coulomb energies of
neighboring nuclei isobars analyzed within the SU(4)-approach for more than 400
nuclei in the mass number range of = 3 - 244. The Wigner SU(4)-symmetry
restoration for heavy and superheavy nuclei is confirmed. It is shown that the
restoration of SU(4)-symmetry does not contradict the possibility of the
existence of the "island of stability" in the region of superheavy nuclei.Comment: 5 pages, 2 figure
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