@article{15c0458865674117b49fdfad5c6fe089,
title = "Thermoelectric power of TTT2I3+δ",
abstract = "We have measured the thermoelectric power of crystals of TTT2I3+δ with conductivity maximum occuring at temperatures from 110 K to 38 K. We find that the metallic state is stabilized to lower temperatures as the samples become less stoichiometric, that the change in electron concentrations on TTT varies by about 5% over this range and that Coulomb correlations are small in this compound.",
author = "Chaikin, {P. M.} and G. Gr{\"u}ner and Shchegolev, {I. F.} and Yagubskii, {E. B.}",
note = "Funding Information: sample. For samples with decreasing T~j~the thermopower indicates both a smaller gap and increased disorder. Several other studies of the transport pro— perties of TTT2I, have been made previously. Most investigators found that with increasing incommensurability or disorder the transitions merely broadened. We can compare our therrno~ower data with results from other laboratories. Most samples which have been prepared in stoi— chiometric form show the same thermopower as seen for ~ = 110 K in both figures 1 and 2. How— ever, none of the previous thermopower studies of disordered samples show the stabilization of the metallic phase to low temperatures that we have found here. Rather they appear as broadened T1~~= 110 K curves. Whereas the conductivity of quasi one— dimensional conductors can change dramatically with imperfection, the themmopower remains unchanged unless the microscopic conduction process has changed. Therefore the thermopower results imply that there is an intrinsic difference between the low TM~ sample described here and the highly disordered samples produced in otherFilnaablolrya,tortihees.themmopower measurements mdi— cate that TTT 2I,÷{\'o}is not a strong Coulomb cor— related system. In the case of split Hubbard bands, a charge density of p = 1.5 corresponds to a half filled upper Hubbard band. In this situation there is a spin contribution of +6OuV/K (positive since the carriers are holes, or more directly S(2—p) —S(p) for the strong coupling Hubbard model) to the themmopower.{\textquoteright}{\textquoteright} In the metallic regime the total thermopower (spin and orbital contributions) would be +6OpV/K -I- AT which should extrapolate to +6OpV/K as T ~- 0. Since this behavior is not found, we can conclude that the Coulomb repulsion is not much greater, and is possibly less, than the bandwidth. This conclusion is in agreement with recent optical studies, which indicate{\textquoteright} that U0 ~ 0.6 eV in TTT compounds, smaller b~about a factor of two than in TCNQ compounds. ~ Together with the larger bandwidth W, TTT corn— pounds appear to be prototypes of weakly cor— related organic conductors. This work was supported by NSF grant DMR 76—83421. One of us (G.G.) acknowledges finan— cial support of grant DNR 77—23577. Copyright: Copyright 2014 Elsevier B.V., All rights reserved.",
year = "1979",
month = dec,
doi = "10.1016/0038-1098(79)90868-8",
language = "English (US)",
volume = "32",
pages = "1211--1214",
journal = "Solid State Communications",
issn = "0038-1098",
publisher = "Elsevier Ltd",
number = "12",
}