TEMPERATURE-DEPENDENCE OF CONDUCTIVITY OF POTASSIUM-DOPED POLY(ACETYLENE) UNDER PRESSURE AND MAGNETIC-FIELD

We have investigated effect of hydrostatic pressure on the dc-conducti vity and the magnetoresistance of potassium doped oriented poly(acetyl ene). Potassium was selected as the counterion based on an in situ con ductivity study of chemical doping with Na, K, Rb and Cs in THF soluti ons. Pressurizing up to 10 kbar increases the conductivities at 295 K and 1.2 K by a factor of two and twenty respectively. At ambient press ure the temperature dependence follows the power law sigma approximate ly T(n) in which n is approximately 0.5. The positive magnetoresistanc e is proportional to the square of the field. We estimated the localiz ation length at 8 and 4 T from analysis of sigma(T,B)in terms of varia ble range hopping. Pressure decreases the magnetoresistance and increa ses the localization length.