Effects of pressure and magnetic field on the low-temperature conductivity of (formula presented)-doped polyacetylene: The influence of scattering by low-energy excitations

The effects of hydrostatic pressure and magnetic field on the low-temperature conductivity of oriented polyacetylene doped with (formula presented) up to a metallic state have been investigated. It was found that the conductivity at 10 kbar 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 resistivity ratio (formula presented) from 2.4 down to 1.9. The temperature dependence of resistivity (formula presented) at temperatures below 1 K at ambient pressure and at 10 kbar, which remains almost unaltered by a magnetic field up to 14 T. The starting temperature of the logarithmic temperature dependence shifts by a magnetic field up to higher temperatures. Transverse magnetoresistance (MR) was found to be negative, linear, and almost temperature-independent at temperatures below 2 K. The low temperature (formula presented) and MR behavior at (formula presented) observed in heavily doped polyacetylene has been attributed to weak localization. We assumed that a dramatic increase of inelastic scattering due to low-energy vibrational excitation can ascribe the stronger temperature behavior of (formula presented) and MR at (formula presented) as a result of further suppression of weak localization due to a more effective dephasing effect. At higher temperature, the resistivity decrease is dominated by activation to additional conduction paths.