A neutron scattering study of two-magnon states in the quantum magnet copper nitrate

TL;DR

This study uses inelastic neutron scattering to investigate two-magnon states in copper nitrate, confirming theoretical predictions of bound states in a dimerized antiferromagnetic chain.

Contribution

First experimental observation of two-magnon bound states in copper nitrate aligning with perturbative theoretical models.

Findings

Measured one and two magnon excitation spectra.

Confirmed the existence of a two-magnon bound state.

Data agrees with perturbative expansion predictions.

Abstract

We report measurements of the two-magnon states in a dimerized antiferromagnetic chain material, copper nitrate (Cu(NO3)2*2.5D2O). Using inelastic neutron scattering we have measured the one and two magnon excitation spectra in a large single crystal. The data are in excellent agreement with a perturbative expansion of the alternating Heisenberg Hamiltonian from the strongly dimerized limit. The expansion predicts a two-magnon bound state for q ~ (2n+1)pi*d which is consistent with the neutron scattering data.