Characterization of the half-filled DMTSA-BF₄ by optical and magnetic measurements

Quasi one-dimensional half-filled radical salt DMTSA-BF₄ shows high conductivity (σ_rt, ≈ 450Ω^-1cm^-1) and the metal-like temperature dependence down to ca. 180K, in contrast to the conventional half-filled organic charge-transfer salts. By the physical properties measurements we characterize the compound as a metal around room temperature due to the large t. On lowering temperature the system undergoes Peierls transition and becomes a semiconductor. Hubbard parameters U_eff and t for DMTSA-BF₄ are estimated at 1.2 eV and 0.36 eV respectively.