Evidence of magnetic mechanism for cuprate superconductivity

TL;DR

This study provides evidence that the superexchange interaction J, influenced by the Cu-O-Cu buckling angle, is the key energy scale controlling superconductivity and related phenomena in cuprate materials.

Contribution

It demonstrates that a single energy scale, J, governs all critical temperatures in cuprates, clarified through systematic chemical modifications and measurements.

Findings

Superexchange interaction J controls critical temperatures.

J is determined by the Cu-O-Cu buckling angle.

Physical parameters can be varied independently in the studied materials.

Abstract

A proper understanding of the mechanism for cuprate superconductivity can emerge only by comparing materials in which physical parameters vary one at a time. Here we present a variety of bulk, resonance, and scattering measurements on the (Ca_xLa_{1-x})(Ba_{1.75-x}La_{0.25+x})Cu_3O_y high temperature superconductors, in which this can be done. We determine the superconducting, Neel, glass, and pseudopage critical temperatures. In addition, we clarify which physical parameter varies, and, equally important, which does not, with each chemical modification. This allows us to demonstrate that a single energy scale, set by the superexchange interaction J, controls all the critical temperatures of the system. J, in-turn, is determined by the in plane Cu-O-Cu buckling angle.