135 K Crystallographic and Electronic Structure of (TMTTF)₂SbF₆

Abstract

Extensive studies of (TMTCF)₂ X salts (where C=T (for sulfur), S (for selenium), and X is a small inorganic anion, i.e. PF₆ ^-, AsF₆ ^-, SbF₆ ^-, ClO₄ ^-,....) have been carried out since the discovery of superconductivity in the first organic compound (TMTSF)₂PF₆ at low temperature (T = 1. 2 K) and high pressure (P = 10 kbar) [1]. An important result of these studies has been the building of a unified (T, P) phase diagram by Caron and Bourbonnais [2] (Fig. 1), which relates the different physical behaviors of the sulfur and selenium compounds: (TMTSF)₂X salts generally evolve at low temperature from a metallic state to an antiferromagnetic (AF) ground state, which is destroyed under moderate pressure, to give rise to superconductivity. Sulfur compounds, on the other hand, exhibit an electronic localization around 120–200 K [3], and reach at lower temperature either a Spin-Peierls (SP) or an AF ground state [4].