Review cuprates -- Anderson's unhappy electrons and their fate

TL;DR

This paper discusses the transition in carrier density in cuprates as doping decreases, linking it to the pseudogap and superconductivity, with a focus on Anderson's concept of 'unhappy' electrons.

Contribution

It provides a broad overview connecting carrier density transitions, pseudogap phenomena, and superconductivity in cuprates, emphasizing Anderson's 'unhappy' electrons.

Findings

Carrier density reduces from 1+p to p holes per copper site.

Connection between carrier transition, pseudogap, and superconductivity.

Highlights the role of Anderson's 'unhappy' electrons in cuprate physics.

Abstract

In cuprates, as doping $p$ is reduced from the overdoped side through the quantum critical point $p^*$, a transition in Hall number density of carriers is observed, in which this number of carriers reduces from $1+p$ holes per copper site to $p$ holes per copper site. The connection of this $1+p$ to $p$ transition with pseudogap and with superconductivity is discussed. A "panoramic" view or a "broad-brush" discussion is presented in which Anderson's "unhappy" electrons take on a central stage.