Electric conductivity of the zero-gap semiconducting state in α-(BEDT-TTF)2I3 salt

Electric conductivity that reveals the zero-gap semiconducting (ZGS) state has been investigated as a function of temperature T and lifetime T in order to understand the ZGS state in a quarter-filled ce(BEDT-TTF)(2)I-3 salt with four sites in the unit cell. By treating tau as a parameter and employing the one-loop approximation, it is found that the conductivity is proportional to T and tau for k(B)T >> h/tau and is independent of T and tau for kBT << h/tau. Further, the conductivity, which is independent of T in the ZGS state, is examined for the impurity scattering in terms of the Born approximation.