engleski

Metal-semiconductor transitions for electrons in kagome planes

(EDT-TTF-CONH2 )6 [Re6 Se8 (CN)6 ] is recently synthesized compound composed of layers with kagome structure.[1] Above 180 K the material is 2D-homogenous bad metal, or semiconductor, depending on pressure ; [2] below 180 K the electrons charge-order into chains, with the antiferromagnetic correlations developing below 100 K.[1] The concentra- tion is 2/3 electrons per node, at which Dirac point coincides with the Fermi level in the weak coupling limit. The experiments imply, however, that electron-electron and electron- phonon interactions are substantial in (EDT-TTF-CONH2)6 [Re6 Se8 (CN)6 ]. At 1/3 filling the kagome lattice exhibits two particular features: the robustness of the Dirac points towards gap opening in the limit of weak electron-electron and electron-phonon couplings ; and the frustration governing charge and spin ordering at strong coupling. For (EDT-TTF-CONH2)6 [Re6 Se8 (CN)6 ] we propose a variety of extended Hubbard –Holstein model to explore the crossovers observed around 180 K and 100 K, charge and spin ordering instabilities, and to examine the conduction mechanism in various phases.

organic metal; bad metal; polaron hopping

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