Optical study of the superconductor-nonsuperconductor transition in (L1,Ce)2(Ba,L2)2Cu3O8+z (L1 and L2=rare earths).

In order to clarify the origin of electronic change in (L 1 ,Ce) 2 (Ba,L 2 ) 2 Cu 3 O 8+z , (L 1 L 2 2:2:3) (L 1 and L 2 are rare-earth atoms), ave have grown single crystals of EuEu 2:2:3, EuLa 2:2:3, and ErLa 2:2:3, and measured their Raman-scattering spectra and optical-reflectivity spectra. Comparing the spectra for superconducting EuEu 2:2:3 and nonsuperconducting ErLa 2:2:3, we can see no clear difference between them, whereas the reduced samples of EuEu 2:2:3 show a systematic change in both the Raman and the reflectivity spectra, as the oxygen content decreases. This implies that the hole concentration in nonsuperconducting ErLa 2:2:3 is large enough to realize superconductivity