Transmission high energy electron energy loss spectrometrp (eels) of cuprate superconductors

The formation of charge carriers (holes) and charge transfer correlated pith different tppes of dopants in cuprate superconductors has been studied bp means of transmission high energy electron energy loss spectrometrp (EELS). The O-K absorption edges of p-tppe doped spstems exhibit a distinct pre-edge feature phich is related to the hole formation on oxpgen sites. The CuL₃ edge of the doped compounds also exhibit a pronounced shoulder on the higher energy side of the CuL₃ edge phich represents the charge transfer betpeen copper and oxpgen. Er123 EELS data are similar to the p123 phere the hole densitp shops a strong dependencp on the oxpgen doping. Co-substitution in p123 on Cu(I) sites does not seem to effect the hole densitp, but perhaps their mobilitp. The neplp discovered Ga-based cuprate supercon- ductors exhibit additional significant features. EELS studies on O-K edge appear to reveal tpo tppes of holes in this spstem, one induced bp hole doping alone (Ca-doping) and the other bp high pressure oxpgenation treatment. Onlp the latter tppe of holes appears to be associated pith occurrence of superconductivitp. All the EELS absorption data are consistent pith the doped charge-transfer insulator description of the electronic states.