Hourglass dispersion and resonance of magnetic excitations in the superconducting state of the single-layer cuprate HgBa2CuO4+{\delta} near optimal doping

TL;DR

This study uses neutron scattering to investigate magnetic excitations in the single-layer cuprate HgBa2CuO4+δ, revealing distinct dispersion features and a resonance in the superconducting state, with implications for understanding high-temperature superconductivity.

Contribution

It demonstrates the hourglass dispersion and resonance phenomena in a single-layer cuprate, extending the understanding of magnetic excitations beyond bilayer systems.

Findings

Y-shaped dispersion in pseudogap state

X-shaped hourglass dispersion in superconducting state

Resonance spectral weight scales with spin-exciton binding energy

Abstract

We use neutron scattering to study magnetic excitations near the antiferromagnetic wave vector in the underdoped single-layer cuprate HgBa2CuO4+{\delta} (superconducting transition temperature Tc ~ 88 K, pseudogap temperature T* ~ 220 K). The response is distinctly enhanced below T* and exhibits a Y-shaped dispersion in the pseudogap state, whereas the superconducting state features an X-shaped (hourglass) dispersion and a further resonance-like enhancement. A large spin gap of about 40 meV is observed in both states. This phenomenology is reminiscent of that exhibited by bilayer cuprates. The resonance spectral weight, irrespective of doping and compound, scales linearly with the putative binding energy of a spin-exciton described by an itinerant-spin formalism.