Band-structure anisotropy and superconducting fluctuations in ditetramethyltetraselenafulvalenium salts(TMTSF)2X

Abstract

This Comment shows that the anisotropy of the band structure of the ${\left(\mathrm{T}\mathrm{M}\mathrm{T}\mathrm{S}\mathrm{F}\right)}_{2}X$ conducting salts derived from experimental data $t_a:t_b:t_c\approx 300:30:1$ is not inconsistent with large superconducting precursor effects around 10 or 15 K. This is a temperature domain which is about 10 times higher than the maximum temperature for the onset of long-range ordered three-dimensional superconductivity ($T_c\approx 1.2$ K). Furthermore, there is a large number of experimental results which are not consistent with single-particle transport properties at low temperature. Likewise the interpretation of the pseudogap and the magnetoresistance in terms of spin-density waves has to our knowledge no experimental support. The existence of superconducting fluctuations seems, at least presently, to be the only consistent interpretation.