Electronic phase diagram of high temperature copper oxide superconductors

TL;DR

This paper investigates the normal state electronic properties of high-temperature copper oxide superconductors, revealing two key temperature scales, T* and Tcoh, that are doping-dependent and critical to understanding superconductivity.

Contribution

It provides a detailed phase diagram of the normal state in cuprates, highlighting the interplay of pseudogap and coherence scales with doping.

Findings

Identification of pseudogap temperature T* and coherence temperature Tcoh.

Observation that T* and Tcoh cross near optimal doping.

Normal state characterized by coherent excitations with an energy gap.

Abstract

In order to understand the origin of high-temperature superconductivity in copper oxides, we must understand the normal state from which it emerges. Here, we examine the evolution of the normal state electronic excitations with temperature and carrier concentration in Bi2Sr2CaCu2O8 using angle-resolved photoemission. In contrast to conventional superconductors, where there is a single temperature scale Tc separating the normal from the superconducting state, the high- temperature superconductors exhibit two additional temperature scales. One is the pseudogap scale T*, below which electronic excitations exhibit an energy gap. The second is the coherence scale Tcoh, below which sharp spectral features appear due to increased lifetime of the excitations. We find that T* and Tcoh are strongly doping dependent and cross each other near optimal doping. Thus the highest superconducting Tc emerges from an unusual normal state that is characterized by coherent excitations with an energy gap.