Stabilisation under pressure of the metallic state in Cs0.83[Pd(C2S2(CN)2)2].0.5H2O at low temperatures

We present results of transport measurements on the linear metal chain system Cs0.83[Pd(C2S2(CN)2)2].0.5H2O. The conduction band in this complex is formed by the overlap of the π-electron orbitals on the dithiolate ligands. Measurements were made under hydrostatic pressures up to 20Kbar and temperatures down to 1.2 K. At ambient pressure the system is semiconducting with a conductivity ∼5 S/cm and an activation energy ∼45 meV. On cooling the system undergoes several semiconductor-semiconductor phase transitions. With increasing pressure the activation energies of the two main phases decrease at 8meV/Kbar. Under a pressure of 18kbar the material is stabilised as a metal down to low temperatures and its resistance is still decreasing at 1.2 K. Thermopower measurements show the majority carriers to be holes for all phases.