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

We study the spectral function A_k(ω) and the optical conductivity σ₁(ω) 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(ω) scales linearly with ω. We demonstrate that σ₁(ω) is inversely linear in ω up to very high frequencies. We argue that the slopes of A_k(ω) and σ₁(ω) agree quantitatively with the photoemission and optical data for Bi2212.