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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
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