Three-dimensionality of field-induced magnetism in a high-temperature superconductor

TL;DR

This study reveals that field-induced magnetism in high-temperature superconductors is three-dimensional, indicating significant interlayer magnetic coupling that coexists with superconductivity and influences vortex behavior.

Contribution

It demonstrates that magnetic order induced by magnetic fields in cuprate superconductors is three-dimensional, contrasting with the predominantly two-dimensional nature of their intrinsic properties.

Findings

Field-induced magnetic order is three-dimensional.

Magnetic linkage exists between CuO2 planes.

Magnetic couplings coexist with superconductivity.

Abstract

Many physical properties of high-temperature (high-Tc) superconductors are two-dimensional phenomena derived from their square planar CuO2 building blocks. This is especially true of the magnetism from the copper ions. As mobile charge carriers enter the CuO2 layers, the antiferromagnetism of the parent insulators, where each copper spin is antiparallel to its nearest neighbours1, evolves into a fluctuating state where the spins show tendencies towards magnetic order of a longer periodicity. For certain charge carrier densities, quantum fluctuations are sufficiently suppressed to yield static long-period order2,3,4,5,6, and external magnetic fields also induce such order7,8,9,10,11,12. Here we show that in contrast to the chemically-controlled order in superconducting samples, the field-induced order in these same samples is actually three-dimensional, implying significant magnetic linkage between the CuO2 planes. The results are important because they show that there are three-dimensional magnetic couplings which survive into the superconducting state, and coexist with the crucial inter-layer couplings responsible for three-dimensional superconductivity. Both types of coupling will straighten the vortex lines, implying that we have finally established a direct link between technical superconductivity, which requires zero electrical resistance in an applied magnetic field and depends on vortex dynamics, and the underlying antiferromagnetism of the cuprates.