C. Rovira et al., STRUCTURAL AND ELECTRONIC-PROPERTIES OF THE ONE-DIMENSIONAL ORGANIC METAL BIS(THIODIMETHYLENE)-TETRATHIAFULVALENE TETRACYANOQUINODIMETHANE, Physical review. B, Condensed matter, 52(12), 1995, pp. 8747-8758
The synthesis and structural characterization at room temperature and
130 K of the organic charge-transfer salt bis(thiodimethylene)-tetrath
iafulvalene tetracyanoquinodimethane (BTDMTTF-TNCQ) is reported. X-ray
diffuse scattering as well as ir and Raman measurements show that the
charge transfer in this salt is similar to 0.5. BTDMTTF-TCNQ remains
metallic down to very low temperatures but exhibits an anomaly at 175
K in the conductivity and thermopower which could be related to some u
nusual structural modification of the unit cell. Band-structure calcul
ations show that this salt is a narrow-band one-dimensional metal. The
high value of the spin susceptibility, the low value of the conductiv
ity, and the observation of a 4k(F) charge-density-wave (CDW) instabil
ity around room temperature prove that it is a highly correlated metal
. In contrast with other salts of the TTF-TCNQ family, BTDMTTF-TCNQ do
es not exhibit critical 2k(F) structural fluctuations. It is proposed
that the absence of the 2k(F) CDW transition is due to the stronger in
terlocking of the donor and acceptor molecules due to the presence of
the sulfur atoms in the central position of the outer five-membered ri
ngs of the BTDMTTF donor.