The order parameter of high temperature superconductors, as measured by Andreev Saint-James reflection, Raman and neutron scattering

TL;DR

This paper demonstrates that Andreev Saint-James reflection, Raman scattering, and neutron scattering techniques all measure the same order parameter in high-temperature cuprate superconductors, revealing its temperature and doping dependence.

Contribution

It shows that multiple experimental methods can consistently measure the superconducting order parameter and clarifies its relation to the pseudogap and BCS-BEC crossover.

Findings

All techniques measure the same order parameter.

The order parameter follows Tc with doping.

At doping x=0.27, the energies coincide, indicating BCS behavior.

Abstract

By comparing experiments that use Andreev Saint-James reflection, Raman scattering (B2g) and neutron scattering on the (cuprate) high temperature superconductors, evidence is found, that all of the techniques can measure the order parameter of these superconductors. The order parameter is the energy needed to take a superconducting boson out of the condensate. It has the same temperature and doping dependence as the superconducting transition temperature Tc. This condensation energy is different from the pairing energy (as measured by the pseudogap) except for the doping x = 0.27, where the two energies coincide: this latter situation represents the BCS case, which in the view presented here is a special case in the BCS-BEC cross-over situation appropriate for the (cuprate) high temperature superconductors.