Neutron spectra of Herbertsmithite Materials: Observation of a Valence Bond Liquid phase?

TL;DR

This paper analyzes neutron spectra in Herbertsmithite, revealing a valence bond liquid phase characterized by localized two-spinon excitations that match experimental neutron scattering data.

Contribution

It provides evidence for a valence bond liquid phase in Herbertsmithite through theoretical analysis of neutron spectra and comparison with experimental data.

Findings

Neutron spectra are dominated by localized two-spinon states.

Dynamic structure factor is spread over a wide frequency range.

Wavevector dependence remains similar to isolated dimers.

Abstract

We argue that neutron spectra in a short-range ordered Valence Bond state is dominated by two-spinon states localized in small spatial regions such as a pinwheel. These excitations lead to angle averaged dynamic structure factor that is spread over a wide frequency range up to about $2.5 J$, whereas its wavevector dependence at all frequencies remains very close to that of isolated dimers. These results are in excellent agreement with recent Neutron scattering data in the Herbertsmithite materials ZnCu$_3$(OH)$_6$Cl$_2$.