Studies on the (non-) existence of “stripes” in high Tc superconductors

Magnetic excitation spectra χ″(q,ω) of YBa2Cu3Oy, La2−xSrxCuO4 and La2−y−xNdySrxCuO4 are compared with those of model calculations. It is important to consider the experimentally observed quasi-particle broadening (Γ) to reproduce the observed spectra of YBa2Cu3Oy, while to reproduce the data of other two systems, very small Γ values, much smaller than those reported in the transport studies 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.