The Hall effect in the organic conductor TTF-TCNQ: Choice of geometry for accurate measurements of highly anisotropic system

TL;DR

This study measures the Hall effect in TTF-TCNQ crystals across various temperatures and geometries, revealing that the Hall coefficient is near zero at high temperatures and can detect phase transitions at lower temperatures, emphasizing the importance of measurement geometry.

Contribution

The paper demonstrates that the Hall coefficient in TTF-TCNQ is geometry-independent and provides insights into phase transitions using Hall effect measurements in a highly anisotropic organic conductor.

Findings

Hall coefficient is approximately zero above 150 K.

Measurement geometry does not affect the Hall coefficient in TTF-TCNQ.

Hall effect can identify all three phase transitions of TTF-TCNQ.

Abstract

We have measured the Hall effect on recently synthesized single crystals of quasi-one-dimensional organic conductor TTF-TCNQ, a well known charge transfer complex that has two kinds of conductive stacks: the donor (TTF) and the acceptor (TCNQ) chains. The measurements were performed in the temperature interval 30 K < T < 300 K and for several different magnetic field and current directions through the crystal. By applying the equivalent isotropic sample (EIS) approach, we have demonstrated the importance of the choice of optimal geometry for accurate Hall effect measurements. Our results show, contrary to past belief, that the Hall coefficient does not depend on the geometry of measurements and that the Hall coefficient value is around zero in high temperature region (T > 150 K), implying that there is no dominance of either TTF or TCNQ chain. At lower temperatures, our measurements clearly prove that all three phase transitions of TTF-TCNQ could be identified from Hall effect measurements.