Transport and optical properties of the hydrazine intercalation complexes of 1T-TaS₂

The reversible interconversion of 1T-TaS 2 with the hydrazine complexes 3R 1.1 TaS 2 (N 2 H 4 ) 4/3 and 3R I TaS 2 (N 2 H 4 ) 2/3 has been studied by thermogravimetric analysis, optical transmission, and electrical resistivity measurements. The low-temperature resistivity of both hydrazine complexes is high, exceeding 10 3 Omega cm when below 20K, and for the 3R I.I complex in rho varies as T -1/3 . This can be interpreted as two-dimensional variable range hopping at the Fermi level, E F , in a system in which the density of states at E F is reduced from the expected metallic value by the presence of a strong Fermi-surface driven structural distortion.