Scaling Behavior of the Longitudinal and Transverse Transport in Quasi One-Dimensional Organic Conductors

TL;DR

This study investigates the anisotropic electrical transport in quasi-one-dimensional organic conductors, revealing a dimensional crossover around 100 K and highlighting differences between the two compounds in their transport behavior.

Contribution

It provides detailed experimental analysis of dc and microwave transport in (TMTSF)$_2$PF$_6$ and (TMTSF)$_2$ClO$_4$, demonstrating a crossover from 1D to higher-dimensional behavior and uncovering unexpected anisotropy features.

Findings

Power-law resistivity behavior below 70 K in (TMTSF)$_2$PF$_6$

Dimensional crossover at approximately 100 K consistent with Luttinger liquid theory

Low anisotropy in (TMTSF)$_2$ClO$_4$ indicating more two-dimensional metallic behavior

Abstract

We report on dc and microwave experiments of the low-dimensional organic conductors (TMTSF)$_2$PF$_6$ and (TMTSF)$_2$ClO$_4$ along the $a$, $b^{\prime}$, and $c^*$ directions. In the normal state of (TMTSF)$_2$PF$_6$ below T=70 K, the dc resistivity follows a power-law with $\rho_a$ and $\rho_{b^{\prime}}$ proportional to $T^2$ while $\rho_{c^*}\propto T$. Above $T = 100$ K the exponents extracted from the data for the $a$ and $c^*$ axes are consiste1nt 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 $b^\prime$ 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 $b^{\prime}$-axis reveal an anomaly between 25 and 55 K which is not understood yet. The organic superconductor (TMTSF)$_2$ClO$_4$ is more a two-dimensional metal with an anisotropy $\rho_a/\rho_{b^{\prime}}$ 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.