Universal properties of cuprate superconductors

TL;DR

This paper explores the universal properties of cuprate superconductors through the lens of quantum critical phenomena, linking empirical correlations to underlying quantum critical lines and transitions.

Contribution

It introduces a scaling theory framework connecting empirical data of cuprates to quantum critical lines and transitions, offering a unified understanding of their universal properties.

Findings

Empirical correlations reflect universal properties of quantum critical flow.

Doping, substitution, and anisotropy tune the flow to quantum critical points.

Flow to 2D-QSI and 3D-QSN criticality is key to understanding superconductivity.

Abstract

To provide an understanding of the universal properties emerging from the empirical correlations and phase diagrams of cuprate superconductors, we invoke the scaling theory of finite temperature and quantum critical phenomena. The universal features are traced back to the existence of quantum critical lines, representing the end lines of the finite temperature transition surface. At the respective quantum critical lines 2D superconductor to insulator (2D-QSI) transitions and 3D superconductor to normal state (3D-QSN) transitions occur. The flow to this quantum critical points is tuned by doping, substitution and anisotropy. It is shown that the empirical correlations, like the dependence of Tc on dopant and substitution concentration, the dependence of Tc on zero temperature in-plane penetration depth, etc., reflect universal properties associated with the flow to these quantum critical points and of the crossover from one to the other. A detailed account of the flow to 2D-QSI and 3D-QSN criticality is a challenge for microscopic theories attempting to solve the puzzle of superconductivity in these materials.