Quantum Magnetic Excitations from Stripes in Copper-Oxide Superconductors

TL;DR

This study investigates magnetic excitations in stripe-ordered copper-oxide superconductors, revealing that quantum effects within stripe models can explain experimental spectra and support the role of stripe correlations in high-temperature superconductivity.

Contribution

It demonstrates that quantum excitations within stripe models can account for magnetic spectra, reinforcing the importance of stripe correlations in cuprate superconductors.

Findings

Magnetic excitation spectra in stripe-ordered La-based cuprates resemble those in YBa2Cu3O6+x.

Naive stripe models cannot explain the observed spectra without considering quantum effects.

Results support stripe correlations as a key component in high-temperature superconductivity.

Abstract

In the copper-oxide parent compounds of the high-transition-temperature superconductors, the valence electrons are localized, one per copper site, due to strong intraatomic Coulomb repulsion. A symptom of the localization is antiferromagnetism, where the spins of localized electrons alternate between up and down. The superconductivity appears when mobile 'holes' are doped into this insulating state, and it coexists with antiferromagnetic fluctuations. In one approach to the coexistence, the holes are believed to self-organize into 'stripes' that alternate with antiferromagnetic (insulating) regions within copper-oxide planes. Such an unusual electronic state would necessitate an unconventional mechanism of superconductivity. There is an apparent problem with this picture, however: measurements of magnetic excitations in superconducting YBa(2)Cu(3)O(6+x) near optimum doping are incompatible with the naive expectations for a material with stripes. Here we report neutron scattering measurements on stripe-ordered La(1.875)Ba(0.125)CuO(4). We show that the measured excitations are, surprisingly, quite similar to those in YBa(2)Cu(3)O(6+x) (i.e., the predicted spectrum of magnetic excitations is wrong). We find instead that the observed spectrum can be understood within a stripe model by taking account of quantum excitations. Our results support the concept that stripe correlations are essential to high-transition-temperature superconductivity.