Low-energy excitations in the magnetized state of the bond-alternating quantum S=1 chain system NTENP

TL;DR

This study uses high-field neutron scattering to explore low-energy excitations in the magnetized phase of NTENP, revealing a broad continuum and multi-magnon features that enhance understanding of its quantum spin dynamics.

Contribution

It provides new experimental insights into the excitation spectrum of NTENP in high magnetic fields, confirming and extending recent numerical predictions.

Findings

Detection of a broad continuum at lower energies.

Observation of a new multi-magnon excitation feature.

Confirmation of the suppression of the lowest-energy gap mode.

Abstract

High intensity inelastic neutron scattering experiments on the S=1 quasi-one-dimensional bond-alternating antiferromagnet Ni(C9D24N4)(NO2)ClO4 (NTENP) are performed in magnetic fields of up to 14.8~T. Excitation in the high field magnetized quantum spin solid (ordered) phase are investigated. In addition to the previously observed coherent long-lived gap excitation [M. Hagiwara et al., Phys. Rev. Lett 94, 177202 (2005)], a broad continuum is detected at lower energies. This observation is consistent with recent numerical studies, and helps explain the suppression of the lowest-energy gap mode in the magnetized state of NTENP. Yet another new feature of the excitation spectrum is found at slightly higher energies, and appears to be some kind of multi-magnon state.