Dynamically dominant excitations of string solutions in the spin-1/2 antiferromagnetic Heisenberg chain in magnetic fields

TL;DR

This paper uses Bethe-ansatz solutions to identify a continuum in the dynamical structure factor of the spin-1/2 antiferromagnetic Heisenberg chain under magnetic fields, connecting low-energy excitations and bound states, with experimental relevance.

Contribution

It reveals a well-defined continuum originating from string solutions, linking zero-field excitations and bound states near saturation, advancing understanding of magnetic excitations in quantum spin chains.

Findings

Identification of a continuum in $S^{+-}(k,)$ from string solutions

Connection between zero-field excitations and bound states near saturation

Experimental validation through comparison with real materials

Abstract

Using Bethe-ansatz solutions, we uncover a well-defined continuum in dynamical structure factor $S^{+-}(k,\omega)$ of the spin-1/2 antiferromagnetic Heisenberg chain in magnetic fields. It comes from string solutions which continuously connect the mode of the lowest-energy excitations in the zero-field limit and that of bound states of overturned spins from the ferromagnetic state near the saturation field. We confirm the relevance to real materials through comparisons with experimental results.