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arXiv · 2610.34536

Quasiparticle Interactions in the $S = 1/2$ Heisenberg Antiferromagnetic Chain CuPzN

Leshan Zhao·Timothy Reeder·Matthew Stone·Daniel G. Mazzone·Jakob Lass·Christof Niedermayer·Daniel H. Reich·Anna Keselman·Oleg A. Starykh·Collin Broholm
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Abstract

We investigate spinon--spinon interactions in the quasi-one-dimensional $S=1/2$ Heisenberg antiferromagnet Cu(C$_4$H$_4$N$_2$)(NO$_3$)$_2$ (CuPzN) using inelastic neutron scattering. At zero field, the spectrum exhibits the canonical multi-spinon continuum of the Heisenberg chain. With increasing field we demonstrate the appearance of an energy gap $2Δ$ towards momentum $q\rightarrow 0$ between the uniform magnetization precession mode and the shifted spinon continuum. $2Δ$ is a direct measure of spinon backscattering interactions. Comparison with numerical matrix-product-state calculations and a recent analytical theory shows excellent agreement. By examining the integrable spin-1/2 chain, we provide an example of how quasiparticle interactions can be quantified experimentally in isotropic quantum spin systems.

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Leshan Zhao, Timothy Reeder, Matthew Stone, Daniel G. Mazzone, Jakob Lass, Christof Niedermayer, Daniel H. Reich, Anna Keselman, Oleg A. Starykh, Collin Broholm. 2026-10-25. Quasiparticle Interactions in the $S = 1/2$ Heisenberg Antiferromagnetic Chain CuPzN. https://arxiv.org/abs/2610.34536

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