Spinons in the strongly correlated copper oxide chains in SrCuO2

TL;DR

This study uses inelastic neutron scattering to explore spin excitations in SrCuO2, revealing a well-described two-spinon continuum that supports the concept of spin-charge separation in strongly correlated 1D electron systems.

Contribution

First direct experimental observation of a two-spinon continuum in SrCuO2 confirming the applicability of the Heisenberg model at high energies.

Findings

Spin excitations form a two-spinon continuum.

Exchange constant J = 226 meV.

Evidence for spin-charge separation in a 1D system.

Abstract

We have investigated the spin dynamics in the strongly correlated chain copper oxide SrCuO$_2$ for energies up to $\gtrsim 0.6$ eV using inelastic neutron scattering. We observe an acoustic band of magnetic excitations which is well described by the "Muller-ansatz" for the two-spinon continuum in the S=1/2 antiferromagnetic Heisenberg spin chain. The lower boundary of the continuum extends up to $\approx 360$ meV, which corresponds to an exchange constant $J = 226(12)$ meV. Our finding that an effective Heisenberg spin Hamlitonian adequately describes the spin sector of this 1D electron system, even though its energy scale is comparable to that of charge excitations, provides compelling experimental evidence for spin-charge separation.