Comment on 'Resonant inelastic x-ray scattering from UOand UN'.

In a recent manuscript, Lawrence Bright(2023175501) reported the resonant inelastic x-ray scattering spectra of UO, as well as UN. Their goal was to identify electronic multiplets associated with a 5configuration with ground state2F5/2. Complete active space self-consistent field with spin-orbit coupling (CASSCF-SOC) predicted that2F5/2transitions should be observable at 190 and 328 meV.

Real-space local self-motion of protonated and deuterated water.

We report on the self-part of the Van Hove correlation function, the correlation function describing the dynamics of a single molecule, of water and deuterated water. The correlation function is determined by transforming inelastic scattering spectra of neutrons or x rays over a wide range of momentum transfer Q and energy transfer E to space R and time t. The short-range diffusivity is estimated from the Van Hove correlation function in the framework of the Gaussian approximation.

Hybrid magnon-phonon localization enhances function near ferroic glassy states.

Ferroic materials on the verge of forming ferroic glasses exhibit heightened functionality that is often attributed to competing long- and short-range correlations. However, the physics underlying these enhancements is not well understood. The NiCoMnIn Heusler alloy is on the edge of forming both spin and strain glasses and exhibits magnetic field-induced shape memory and large magnetocaloric effects, making it a candidate for multicaloric cooling applications.

Chiral and flat-band magnetic quasiparticles in ferromagnetic and metallic kagome layers.

Magnetic kagome metals are a promising platform to develop unique quantum transport and optical phenomena caused by the interplay between topological electronic bands, strong correlations, and magnetic order. This interplay may result in exotic quasiparticles that describe the coupled electronic and spin excitations on the frustrated kagome lattice. Here, we observe novel elementary magnetic excitations within the ferromagnetic Mn kagome layers in TbMnSn using inelastic neutron scattering.

Orbital character of the spin-reorientation transition in TbMnSn.

Ferromagnetic (FM) order in a two-dimensional kagome layer is predicted to generate a topological Chern insulator without an applied magnetic field. The Chern gap is largest when spin moments point perpendicular to the kagome layer, enabling the capability to switch topological transport properties, such as the quantum anomalous Hall effect, by controlling the spin orientation. In TbMnSn, the uniaxial magnetic anisotropy of the Tb ion is effective at generating the Chern state within the FM Mn kagome layers while a spin-reorientation (SR) transition to easy-plane order above T = 310 K provides a mechanism for switching.

Diffusive excitonic bands from frustrated triangular sublattice in a singlet-ground-state system.

Magnetic order in most materials occurs when magnetic ions with finite moments arrange in a particular pattern below the ordering temperature. Intriguingly, if the crystal electric field (CEF) effect results in a spin-singlet ground state, a magnetic order can still occur due to the exchange interactions between neighboring ions admixing the excited CEF levels. The magnetic excitations in such a state are spin excitons generally dispersionless in reciprocal space.

Dynamic crystallography reveals spontaneous anisotropy in cubic GeTe.

Cubic energy materials such as thermoelectrics or hybrid perovskite materials are often understood to be highly disordered. In GeTe and related IV-VI compounds, this is thought to provide the low thermal conductivities needed for thermoelectric applications. Since conventional crystallography cannot distinguish between static disorder and atomic motions, we develop the energy-resolved variable-shutter pair distribution function technique.

Phason-Dominated Thermal Transport in Fresnoite.

Fast-propagating waves in the phase of incommensurate structures, called phasons, have long been argued to enhance thermal transport. Although supersonic phason velocities have been observed, the lifetimes, from which mean free paths can be determined, have not been resolved. Using inelastic neutron scattering and thermal conductivity measurements, we establish that phasons in piezoelectric fresnoite make a major contribution to thermal conductivity by propagating with higher group velocities and longer mean free paths than phonons.

Magnetic molecular orbitals in MnSi.

A large body of knowledge about magnetism is attained from models of interacting spins, which usually reside on magnetic ions. Proposals beyond the ionic picture are uncommon and seldom verified by direct observations in conjunction with microscopic theory. Here, using inelastic neutron scattering to study the itinerant near-ferromagnet MnSi, we find that the system's fundamental magnetic units are interconnected, extended molecular orbitals consisting of three Mn atoms each rather than individual Mn atoms.

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.

Real-Space Local Dynamics of Molten Inorganic Salts Using Van Hove Correlation Function.

Molten inorganic salts are attracting resurgent attention because of their unique physicochemical properties, making them promising media for next-generation concentrating solar power systems and molten salt reactors. The dynamics of these highly disordered ionic media is largely studied by theoretical simulations, while the robust experimental techniques capable of observing local dynamics are not well-developed. To provide fundamental insights into the atomic-scale transport properties of molten salts, we report the real-space dynamics of molten magnesium chloride at high temperatures employing the Van Hove correlation function obtained by inelastic neutron scattering.

Spiral Spin Liquid on a Honeycomb Lattice.

Spiral spin liquids are correlated paramagnetic states with degenerate propagation vectors forming a continuous ring or surface in reciprocal space. On the honeycomb lattice, spiral spin liquids present a novel route to realize emergent fracton excitations, quantum spin liquids, and topological spin textures, yet experimental realizations remain elusive. Here, using neutron scattering, we show that a spiral spin liquid is realized in the van der Waals honeycomb magnet FeCl_{3}.

Soft anharmonic phonons and ultralow thermal conductivity in Mg(Sb, Bi) thermoelectrics.

The candidate thermoelectric compounds MgSb and MgBi show excellent performance near ambient temperature, enabled by an anomalously low lattice thermal conductivity (κ) comparable to those of much heavier PbTe or BiTe Contrary to common mass-trend expectations, replacing Mg with heavier Ca or Yb yields a threefold increase in κ in CaMgSb and YbMgBi Here, we report a comprehensive analysis of phonons in the series Mg ( = Mg, Ca, and Yb; = Bi and Sb) based on inelastic neutron/x-ray scattering and first-principles simulations and show that the anomalously low κ of Mg has inherent phononic origins. We uncover a large phonon softening and flattening of low-energy transverse acoustic phonons in Mg compared to the ternary analogs and traced to a specific Mg- bond, which markedly enlarges the scattering phase-space, enabling the threefold tuning in κ These results provide key insights for manipulating phonon scattering without the traditional reliance on heavy elements.

Two-dimensional overdamped fluctuations of the soft perovskite lattice in CsPbBr.

Lead halide perovskites exhibit structural instabilities and large atomic fluctuations thought to impact their optical and thermal properties, yet detailed structural and temporal correlations of their atomic motions remain poorly understood. Here, these correlations are resolved in CsPbBr crystals using momentum-resolved neutron and X-ray scattering measurements as a function of temperature, complemented with first-principles simulations. We uncover a striking network of diffuse scattering rods, arising from the liquid-like damping of low-energy Br-dominated phonons, reproduced in our simulations of the anharmonic phonon self-energy.

Magnetic order and fluctuations in the quasi-two-dimensional planar magnet .

We use neutron scattering to investigate spin excitations in , which has a -axis incommensurate helical structure of the two-dimensional (2D) in-plane ferromagnetic (FM) ordered layers for . By comparing the wave vector and energy dependent spin excitations in helical ordered and paramagnetic , we find that Ni doping, while increasing lattice disorder in , enhances quasi-2D FM spin fluctuations. However, our band structure calculations within the combined density functional theory and dynamic mean field theory (DFT+DMFT) failed to generate a correct incommensurate wave vector for the observed helical order from nested Fermi surfaces.

Anharmonic Origin of the Giant Thermal Expansion of NaBr.

All phonons in a single crystal of NaBr are measured by inelastic neutron scattering at temperatures of 10, 300, and 700 K. Even at 300 K, the phonons, especially the longitudinal-optical phonons, show large shifts in frequencies and show large broadenings in energy owing to anharmonicity. Ab initio computations are first performed with the quasiharmonic approximation (QHA) in which the phonon frequencies depend only on V and on T only insofar as it alters V by thermal expansion.

Observation of High-Frequency Transverse Phonons in Metallic Glasses.

Using inelastic neutron scattering and molecular dynamics simulations on a model Zr-Cu-Al metallic glass, we show that transverse phonons persist well into the high-frequency regime, and can be detected at large momentum transfer. Furthermore, the apparent peak width of the transverse phonons was found to follow the static structure factor. The one-to-one correspondence, which was demonstrated for both Zr-Cu-Al metallic glass and a three-dimensional Lennard-Jones model glass, suggests a universal correlation between the phonon dynamics and the underlying disordered structure.

Experimental determination of the temperature-dependent Van Hove function in a ZrPt liquid.

Even though the viscosity is one of the most fundamental properties of liquids, the connection with the atomic structure of the liquid has proven elusive. By combining inelastic neutron scattering with the electrostatic levitation technique, the time-dependent pair-distribution function (i.e.

Anharmonic lattice dynamics and superionic transition in AgCrSe.

Intrinsically low lattice thermal conductivity ([Formula: see text]) in superionic conductors is of great interest for energy conversion applications in thermoelectrics. Yet, the complex atomic dynamics leading to superionicity and ultralow thermal conductivity remain poorly understood. Here, we report a comprehensive study of the lattice dynamics and superionic diffusion in [Formula: see text] from energy- and momentum-resolved neutron and X-ray scattering techniques, combined with first-principles calculations.

Coexistence of Ferromagnetic and Stripe Antiferromagnetic Spin Fluctuations in SrCo_{2}As_{2}.

We use inelastic neutron scattering to study energy and wave vector dependence of spin fluctuations in SrCo_{2}As_{2}, derived from SrFe_{2-x}Co_{x}As_{2} iron pnictide superconductors. Our data reveal the coexistence of antiferromagnetic (AF) and ferromagnetic (FM) spin fluctuations at wave vectors Q_{AF}=(1,0) and Q_{FM}=(0,0)/(2,0), respectively. By comparing neutron scattering results with those of dynamic mean field theory calculation and angle-resolved photoemission spectroscopy experiments, we conclude that both AF and FM spin fluctuations in SrCo_{2}As_{2} are closely associated with a flatband of the e_{g} orbitals near the Fermi level, different from the t_{2g} orbitals in superconducting SrFe_{2-x}Co_{x}As_{2}.

Response to comment on "Giant electromechanical coupling of relaxor ferroelectrics controlled by polar nanoregion vibrations".

Gehring . argue that a splitting observed by us in the transverse acoustic (TA) phonon in the relaxor ferroelectric Pb[(MgNb) Ti ]O with = 0.30 (PMN-30PT) is caused by a combination of inelastic-elastic multiple scattering processes called ghostons.

Frustrated magnetic interactions in an = 3/2 bilayer honeycomb lattice compound BiMnO(NO).

An inelastic neutron scattering study has been performed in an = 3/2 bilayer honeycomb lattice compound BiMnO(NO) at ambient and high magnetic fields. Relatively broad and monotonically dispersive magnetic excitations were observed at ambient field, where no long-range magnetic order exists. In the magnetic-field-induced long-range ordered state at 10 T, the magnetic dispersions become slightly more intense, albeit still broad as in the disordered state, and two excitation gaps, probably originating from an easy-plane magnetic anisotropy and intrabilayer interactions, develop.

Discovery of coexisting Dirac and triply degenerate magnons in a three-dimensional antiferromagnet.

Topological magnons are emergent quantum spin excitations featured by magnon bands crossing linearly at the points dubbed nodes, analogous to fermions in topological electronic systems. Experimental realisation of topological magnons in three dimensions has not been reported so far. Here, by measuring spin excitations (magnons) of a three-dimensional antiferromagnet CuTeO with inelastic neutron scattering, we provide direct spectroscopic evidence for the coexistence of symmetry-protected Dirac and triply degenerate nodes, the latter involving three-component magnons beyond the Dirac-Weyl framework.

Glassy Phonon Heralds a Strain Glass State in a Shape Memory Alloy.

Shape memory strain glasses are frustrated ferroelastic materials with glasslike slow relaxation and nanodomains. It is possible to change a NiCoMnIn Heusler alloy from a martensitically transforming alloy to a nontransforming strain glass by annealing, but minimal differences are evident in the short- or long-range order above the transition temperature-although there is a structural relaxation and a 0.18% lattice expansion in the annealed sample.