Magnetic excitations of the Cu$^{2+}$ quantum spin chain in Sr$_3$CuPtO$_6$

TL;DR

This study investigates the magnetic excitation spectrum of Sr$_3$CuPtO$_6$ using inelastic neutron scattering, revealing gapless spinon excitations consistent with a 1D quantum spin chain and indications of weak interchain interactions.

Contribution

The paper provides the first detailed neutron scattering analysis of Sr$_3$CuPtO$_6$, modeling its excitations with 2+4 spinon contributions and identifying weak interchain coupling effects.

Findings

Magnetic excitations persist above 100 K with broadening.

No spin gap observed, consistent with gapless spinons.

Weak interchain coupling influences temperature dependence.

Abstract

We report the magnetic excitation spectrum as measured by inelastic neutron scattering for a polycrystalline sample of Sr$_3$CuPtO$_6$. Modeling the data by the 2+4 spinon contributions to the dynamical susceptibility within the chains, and with interchain coupling treated in the random phase approximation, accounts for the major features of the powder-averaged structure factor. The magnetic excitations broaden considerably as temperature is raised, persisting up to above 100 K and displaying a broad transition as previously seen in the susceptibility data. No spin gap is observed in the dispersive spin excitations at low momentum transfer, which is consistent with the gapless spinon continuum expected from the coordinate Bethe ansatz. However, the temperature dependence of the excitation spectrum gives evidence of some very weak interchain coupling.