Spinon continuum in the Heisenberg quantum spin-chain compound Sr₂V₃O₉

We use inelastic neutron scattering to probe the magnetic excitations in a single crystal sample of the proposed S=1/2 linear chain antiferromagnet Sr₂V₃O₉. The primary excitations associated with the S=1/2 linear chain Heisenberg antiferromagnet are fractional quasiparticles known as spinons. A spinon continuum with a bandwidth of approximately 22 meV is found to exist Sr₂V₃O₉. We observe that the magnetic chain axis is along a direction nearly perpendicular to the apparent structural chains which exist in the compound. Although the system exhibits long range magnetic order below T_N~5 K, we can consistently reproduce the spinon spectrum over a range of higher temperatures and energy transfers via comparisons to Bethe ansatz calculations, matrix renormalization group (DMRG) calculations, and effective field theories near the antiferromagnetic zone center.

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