First-Principles Phonon Calculations for LA2CUO4

Abstract

AbstractFull potential linearized augmented plane wave (LAPW) total energy calculations predict that the breathing mode in La2CuO4 is a high frequency mode, in agreement with experiment and contrary to previously published results. We also find the experimentally observed tilt mode to be unstable within the local density approximation (LDA). Eight other modes were studied, as well as the static structural parameters, and excellent agreement with experiment was found, indicating that LDA gives accurate total energies and static density response for the high temperature superconductors. Our results also suggest that phonons in the high Tc superconductors are not heavily dressed by magnetic or excitonic fluctuations, and thus that the isotope effect observed in the oxide superconductors is probably due to direct involvement of phonons in the superconductivitymechanism.