High frequency modes of YBa2Cu3O6+x and their variation with the oxygen content x☆

Abstract Neutron inelastic scattering spectra of YBa 2 Cu 3 O 6+ x samples with various oxygen contents x have been measured in the ra from 10 to 150 meV with a new type of Be-filter detector spectrometer at the CIAE, Beijing. In semiconducting samples with x =0 and x =0.2, some strong high frequency modes (HFMs) are observed in the range from 60 to 150 meV. However, HFMs are not present in superconducting samples with x =0.78 and 0.97. An anomalous inelastic scattering intensity of the sample with x ⩽0.2 is about two to three times stronger that that with x =0.78 and 0.97 in the measured energy range from 10 to 150 meV.