Universality of Critical Exponents in Conducting Polymers

Scaling analysis of conductivity is carried out to find the critical exponents near the metal–insulator transition (MIT) and the role of disorder and carrier density in charge transport of conducting polymers. Using a single scaling function, a scaling analysis of conductivity is performed on four different conducting polymers. The conductivity of metallic samples fits the upper branch of the scaling equation, while that of insulating samples fits the lower branch, giving critical exponents such as conductivity exponent μ ≈ 1, correlation length exponent ν ≈ 1, and dynamic exponent z ≈ 2.5. Despite the complexity of conducting polymers, the consistent values of critical exponents demonstrate the intriguing property of universality near MIT.