In 1991, V. J. Emery in his important review article entitled “Some aspects of the theory of high temperature superconductors” (Emery, Phys. B: Condens. Matter. 169, 17–25 1991) argued against the Zhang-Rice reduction of three-band to an effective one-band model. In his words “...therefore it seems that the simple \(t-J\) model does not account for the properties of high temperature superconductors”. Over approximately 35 years after the initial debates much has happened in the field pertaining to this topic. Even though it is one of the most discussed issue, a comprehensive account and the required resolution are lacking. Connected to the debate over one-band versus three-band models is another discussion: the one-component versus two-component model for cuprates. The two-component model is most strongly advocated by Barzykin and Pines (Adv. Phys. 58, 1–65 2009). In this article the author attempts a perspective and a re-look on some of these issues. After an analysis of a large body of literature, author finds that V. J. Emery’s criticism of the Zhang-Rice reduction was correct. Many central experimental features of cuprates cannot be rationalized within the one-band model, and Johnston-Nakano scaling is one such example. Other examples are also discussed. Author introduces a simple-minded toy model to illustrate the core issues involved.
