The effects of pressure and magnetic field on the charge transport of heavily FeCl4 - doped polyacetylene

Abstract

The effects of hydrostatic pressure and magnetic field on the charge transport of oriented polyacetylene (PA) films heavily doped with FeCl4 - have been studied in the temperature range 0.37-300 K. It was found that application of pressure increases the room temperature conductivity and decreases the resistivity ratio ρr = ρ(0.37 K)/ρ(300 K) by ∼20-30%. At T < 2 K the temperature dependence of resistivity ρ(T) ∼ln T at ambient pressure and at 10 kbar. Transverse magnetoresistance (MR) at 10 kbar was found to be negative, linear and almost temperature independent at T < 2 K. The observed low temperature ρ(T) and MR behavior has attributed to weak localization which accompanied by the effect of saturation of electron dephasing by two-level systems of a special type. The stronger behavior of ρ(T) and MR at T > 2 K has associated with further suppression of weak localization due to more effective dephasing effect by low energy vibrational excitations. © 2002 Elsevier Science B.V. All rights reserved.