Spin-phonon coupling, q-dependence of spin excitations and high-TC superconductivity from band models
Abstract
An understanding of spin excitations in cuprates is essential since the mechanism of high-TC superconductivity might be linked to spin fluctuations. Band calculations for long "1-dimensional" unit cells of La2CuO4 show that the coupling between antiferromagnetic spin waves and phonons is larger for distortions of oxygens than for Cu or La. When this result is applied to a 2-dimensional, free-electron like band, it leads to a q-dependent spin excitation spectrum in good agreement with recent experiments. It is argued that important parameters for spin-phonon coupling, which comes out from the comparison between experiment and theory, are relevant for the mechanism of superconductivity, and are large enough to explain a high TC.
0