Enhancement of susceptibility and the electrical resistivity of organic metals with a small mean free path

Abstract

The spin susceptibility of organic metals is enhanced over the Pauli value at ambient temperature, where the mean free path is close to one lattice constant. The resistivity continues to follow the T ² law in this regime. A theory is described which accounts for these unusual effects. The theory is somewhat analogous to polaron theory and makes use of the quadratic nature of the electron-phonon coupling. The electrons are localized by short-lived “phonon traps”, accounting for the transition to a Curie-like behaviour. Tunnelling between these nun-degenerate molecular sites gives rise to a T ² law with a coefficient close to that of the low-temperature state, where the conductivity is metallic.