Effects of pressure and magnetic field on the low-temperature conductivityof FeCl4--doped polyacetylene: The influence of scattering by low-energy excitations - art. no. 235209

The effects of hydrostatic pressure and magnetic field on the low-temperatu re conductivity of oriented polyacetylene doped with FeCl4- up to a metalli c state have been investigated It was found that the conductivity at 10 kba r is greater than that at ambient pressure by a factor of 1.3. Application of pressure suppresses the resistivity minimum at 280 K and decreases the r esistivity ratio rho (r)=rho (0.37 K)/rho (300 K) from 2.4 down to 1.9. The temperature dependence of resistivity rho (T)similar to In T at temperatur es below 1 K at ambient pressure and at 10 kbar, which remains almost unalt ered by a magnetic field up to 14 T. The starting temperature of the logari thmic temperature dependence shifts by a magnetic field up to higher temper atures. Transverse magnetoresistance (MR) was found to be negative, linear, and almost temperature-independent at temperatures below 2 K. The low temp erature rho (T) and MR behavior at T<1 K observed in heavily doped polyacet ylene has been attributed to weak localization. We assumed that a dramatic increase of inelastic scattering due to low-energy vibrational excitation c an ascribe the stronger temperature behavior of <rho>(T) and MR at T>2 K as a result of further suppression of weak localization due to a more effecti ve dephasing effect. At higher temperature, the resistivity decrease is dom inated by activation to additional conduction paths.