Mutual spin-phonon driving effects and phonon eigenvector renormalization in nickel (II) oxide

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 119; no. 29; pp. 1 - 7
• Main Authors: Sun, Qiyang, Wei, Bin, Su, Yaokun, Smith, Hillary, Lin, Jiao Y. Y., Abernathy, Douglas L., Li, Chen
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 19.07.2022
• Subjects: Acoustic properties; Acoustics; anomalous inelastic neutron scattering intensity; Antiferromagnetism; Coupling; Eigenvectors; Electron spin; Elementary excitations; First principles; Inelastic scattering; Magnetostriction; Momentum transfer; Neutron scattering; Neutrons; Nickel; phonon dynamics; phonon eigenvector renormalization; Phonons; Physical Sciences; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Scattering cross sections; spin-phonon coupling; Transport phenomena; Transport processes; Wave dispersion; spin-phonon coupling; anomalous inelastic neutron scattering intensity; phonon dynamics; phonon eigenvector renormalization
• DOI: 10.1073/pnas.2120553119
• ISSN: 0027-8424; 1091-6490

The physics of mutual interaction of phonon quasiparticles with electronic spin degrees of freedom, leading to unusual transport phenomena of spin and heat, has been a subject of continuing interests for decades. Despite its pivotal role in transport processes, the effect of spin-phonon coupling on the phonon system, especially acoustic phonon properties, has so far been elusive. By means of inelastic neutron scattering and first-principles calculations, anomalous scattering spectral intensity from acoustic phonons was identified in the exemplary collinear antiferromagnetic nickel (II) oxide, unveiling strong spin-lattice correlations that renormalize the polarization of acoustic phonon. In particular, a clear magnetic scattering signature of the measured neutron scattering intensity from acoustic phonons is demonstrated by its momentum transfer and temperature dependences. The anomalous scattering intensity is successfully modeled with a modified magneto-vibrational scattering cross-section, suggesting the presence of spin precession driven by phonon. The renormalization of phonon eigenvector is indicated by the observed “geometry-forbidden” neutron scattering intensity from transverse acoustic phonon. Importantly, the eigenvector renormalization cannot be explained by magnetostriction but instead, it could result from the coupling between phonon and local magnetization of ions.