Optical conductivity of electron-doped cuprates, pseudogap and antiferromagnetic fluctuations

Recent neutron scattering experiments on electron-doped cuprates have shown that the antiferromagnetic correlation length at the pseudogap temperature scales like the thermal de Broglie wavelength. This result, predicted by the Two-Particle Self-Consistent approach (TPSC), suggests that antiferromagnetic fluctuations are at the origin of the pseudogap in electron-doped cuprates. Clearly one needs to verify that other physical properties can also be explained within the same formalism. We thus derive, within TPSC, the formula appropriate for optical conductivity, including the first vertex correction. Our numerical calculations then show that, as observed experimentally, there is a transfer of spectral weight from low to high energy when antiferromagnetic correlations become important near the pseudogap temperature.