Spin Gap in Optimally-doped YBCO

TL;DR

This study uses inelastic neutron scattering to investigate the spin gap in optimally-doped YBCO, revealing a sharp spectral onset at 33 meV that remains unchanged across the superconducting transition.

Contribution

It provides detailed measurements of the spin gap in YBCO, showing that the gap does not soften or fill in at Tc, which advances understanding of magnetic excitations in high-temperature superconductors.

Findings

Spectral weight has a step function shape at 10K.

No spectral weight at 31 meV, full at 35 meV.

Spin gap remains unchanged across Tc.

Abstract

Spin gap in optimally-doped YBCO was investigated by inelastic neutron scattering. We found that q-integrated spectral weight in the vicinity of the spin gap has a shape of a step function at 10K with sharp resolution-limited onset at 33 meV, i.e. there is no observable spectral weight at 31 meV but full spectral weight at 35 meV. The spin gap does not soften or "fill in" as the temperature is increased to Tc. Above Tc we find no evidence for q-dependent magnetic signal at 35 meV.