Scaling behavior of the longitudinal and transverse transport in quasi-one-dimensional organic conductors

摘要

We report on dc and microwave experiments of the low-dimensional organic conductors (TMTSF)_2PF_6 and (TMTSF)_2C1O_4 along the a, b′, and c~* directions. In the normal state of (TMTSF)_2PF_6 below T=70 K, the dc resistivity follows a power law with ρ_a and ρ_b, proportional to T~2 while ρ_c*∝ T. Above T= 100 K the exponents extracted from the data for the a and c~* axes are consistent with what is to be expected for a system of coupled one-dimensional chains (Luttinger liquid) and a dimensional crossover at a temperature of about 100 K. The b′ axis shows anomalous exponents that could be attributed to a large crossover between these two regimes. The contactless microwave measurements of single crystals along the b′ axis reveal an anomaly between 25 and 55 K which is not understood yet. The organic superconductor (TMTSF)_2ClO_4 is more a two-dimensional metal with an anisotropy ρ_a/ρ_b′ of approximately 2 at all temperatures. Such a low anisotropy is unexpected in view of the transfer integrals. Slight indications to one-dimensionality are found in the temperature dependent transport only above 200 K. Even along the least conducting c~* direction no region with semiconducting behavior is revealed up to room temperature.