Spectral function and conductivity in the normal state of the cuprates: a spin fluctuation study

Abstract

We study the spectral function $A_k (\omega)$ and the optical conductivity $\sigma_1 (\omega)$ for a system of fermions interacting with their collective spin fluctuations (the spin-fermion model), and apply the results to optimally doped cuprates in the normal state. We show that there is no qualitative distinction between hot and cold regions in the Brillouin zone - in both cases, there exists a wide range of frequencies where the width of the peak in $A_k (\omega)$ scales linearly with $\omega$. We demonstrate that $\sigma_1 (\omega)$ is inversely linear in $\omega$ up to very high frequencies. We argue that these results agree {\it quantitatively} with the photoemission and optical data for $Bi2212$.