The longitudinal spin-conductivity of τ-type organic conductors

Abstract

The Kubo formula is used to evaluate the real part of the longitudinal spin conductivity for τ -type organic layered conductors. These conductors are described by a four-band model, consisting of the tight binding Hamiltonian of the system. This Hamiltonian may be written as a direct sum of two two-band models, describing the spins up and down respectively. The longtudinal spin conductivity of the system is analytically evaluated by means of Kubo formula applied to the two-band model corresponding to the spin up carriers. Our results show that the regular real part of the longitudinal spin-conductivity of the system becomes zero for sufficiently large values of the spin–orbit coupling constant ( λ > 0 . 04 ) and only ballistic propagation occurs in this case. The ballistic propagation is more favourable for smaller values of the temperature in the system studied here.