4 research outputs found
Neutron Scattering Signature of Phonon Renormalization in Nickel (II) Oxide
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.Comment: Research pape
Matryoshka Phonon Twinning in alpha-GaN
Understanding lattice dynamics is crucial for effective thermal management in
high-power electronic devices because phonons dominate thermal transport in
most semiconductors. This study utilizes complementary inelastic X-ray and
neutron scattering techniques and reports the temperature-dependent phonon
dynamics of alpha-GaN, one of the most important third-generation power
semiconductors. A prominent Matryoshka phonon dispersion is discovered with the
scattering tools and confirmed by the first-principles calculations. Such
Matryoshka twinning throughout the three-dimension reciprocal space is
demonstrated to amplify the anharmonicity of the related phonon modes through
creating abundant three-phonon scattering channels and cutting the phonon
lifetime of affected modes by more than 50%. Such phonon topology effectively
contributes to the reduction of the in-plane thermal transport, thus the
anisotropic thermal conductivity of alpha-GaN. The results not only have
significant implications for engineering the thermal performance and other
phonon-related properties of alpha-GaN, but also offer valuable insights on the
role of anomalous phonon topology in thermal transport of other technically
important semiconductors.Comment: 34 pages, 15 figure
Frustration-induced diffusive scattering anomaly and dimension change in
Magnetic frustration, arising from the competition of exchange interactions,
has received great attention because of its relevance to exotic quantum
phenomena in materials. In the current work, we report an unusual
checkerboard-shaped scattering anomaly in , far from the known
incommensurate magnetic satellite peaks, for the first time by inelastic
neutron scattering. More surprisingly, such phenomenon appears as spin dynamics
at low temperature, but it becomes prominent above N\'eel transition as elastic
scattering. A new model Hamiltonian that includes an intraplane next-nearest
neighbor was proposed and attributes such anomaly to the near-perfect magnetic
frustration and the emergence of unexpected two-dimensional magnetic order in
the quasi-one-dimensional .Comment: 24 pages, 10 figure
Mutual spin-phonon driving effects and phonon eigenvector renormalization in nickel (II) oxide
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