title: Quantum spin metal state on a decorated honeycomb lattice.
abstract: We present a modification of the 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 whose size depends on the ratio of exchange couplings. Low-temperature heat capacity C(T) and dynamic spin susceptibility χ(ω,T) are calculated in the case of small Fermi circle. Whereas, C(T)∼T at low temperatures as it is expected for a Fermi liquid, spin excitations are gapped and χ(ω,T) demonstrates unusual behavior with a power-law peak near the resonance frequency. The corresponding exponent as well as the peak shape are calculated.
authors.affiliation: L. D. Landau Institute for Theoretical Physics, Kosygin Street 2, Moscow 119334, Russia.
authors.forename: K S
authors.initials: KS
authors.lastname: Tikhonov
authors.forename: M V
authors.initials: MV
authors.lastname: Feigel'man