Studies on Magnetic Excitation Spectra of High-Tc Superconductors

TL;DR

This study compares magnetic excitation spectra of various high-Tc superconductors with model calculations, highlighting the importance of quasiparticle broadening and possible stripe correlations in explaining experimental data.

Contribution

It introduces a model incorporating quasiparticle broadening and compares it with experimental spectra, suggesting stripe correlations influence the spectra in high-Tc superconductors.

Findings

Quasiparticle broadening G is crucial for matching spectra in YBa2Cu3Oy.

Small G values are needed for La-based cuprates, indicating stripe correlations.

Stripe fluctuations may affect magnetic excitation spectra.

Abstract

Magnetic excitation spectra c"(q,w) of YBa2Cu3Oy, La2-xSrxCuO4, La2-y-xNdySrxCuO4 and Nd2-xCexCuO4 are compared with those of model calculations, where q and w are the wave vector and the energy of the excitations. In the model, the dynamical spin susceptibility is calculated by the expression c(q,w)= c0(q,w)/{1+J(q)c0(q,w)}, where c0(q,w) is obtained by adopting the effective energy dispersion of the quasi particles which can reproduce the shapes of the Fermi surface, and J(q) is the exchange coupling between the Cu-Cu electrons. It is important to consider the experimentally observed quasi particle broadening (G) to reproduce the observed spectra of YBa2Cu3Oy, while to reproduce the data of La2-xSrxCuO4 and La2-y-xNdySrxCuO4, very small G values have to be used, even in the phases without the static "stripe" order. This may be caused by the existence of the "stripe" correlations or "stripe" fluctuations.