Experimental investigation of the electronic states in high Tc copper oxides

Abstract

Abstract Current status of the research is described focusing on the experimental investigation of the unique electronic states in the high T c superconducting oxides. A common feature of all the high T c oxides is the quasi two-dimensional motion of carriers within CuO 2 planes. The carriers are holes which appear to reside in a band with width much narrower than the band-calculation value. No evidence has so far been obtained which indicates a relevance of the electron-phonon interaction, whereas the models emphasizing the electron correlation are reinforced by the observation of an antiferromagnetic order in La 2 CuO 4 and the fact that numerous paramagnetic spins appear when the oxygen content is reduced in YBa 2 Cu 3 O 7- y .