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The metal‐ferroelectric transition in TTF‐TCNQ
Author(s) -
Cohen Morrel H.,
Hertz John A.,
Horn Paul M.,
Shante Vinod K. S.
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560080853
Subject(s) - condensed matter physics , superconductivity , ferroelectricity , stacking , materials science , distortion (music) , metal , band gap , coupling (piping) , perpendicular , transition metal , physics , chemistry , optoelectronics , nuclear magnetic resonance , amplifier , geometry , mathematics , cmos , dielectric , metallurgy , biochemistry , catalysis
Abstract Earlier incorrect proposals for organic superconductors have the virtue of pinpointing the need for a deeper understanding of the metallic state in organic materials. Accordingly, we consider the effects of interstack coupling on the electronic band structure of TTF‐TCNQ, showing that a one‐electron theory predicts semimetallic behavior. We argue, however, that this state is unstable at low T against a ferroelectric distortion perpendicular to the stacking axis, which produces a gap. With increasing T , the gap is filled by states which are localized (in the Anderson sense) by thermal disorder on individual stacks, thereby restoring one‐dimensional metallic conductivity.