Half-Heusler (HH) compounds are promising thermoelectric (TE) materials, but their intrinsically high lattice thermal conductivity (κL) limits TE performance. Here, we report sublattice softening-induced intrinsically low κL and exceptional thermoelectricity in the previously underexplored rare-earth (RE) containing HHs. Unlike conventional non-RE HHs, the softened RE-based lattice framework in RE-HHs enables vigorous atom vibration within the 4c sublattice, strengthening lattice anharmonicity and phonon damping. This effect can be further amplified when heavier elements occupy the 4c sublattice, effectively suppressing both acoustic and optical phonon propagation and resulting in a pronounced reduction in κL. Leveraging the low κL, we identify four RE-HHs-DyPtSb, Y0.7Lu0.3PtSb, Sc0.6Lu0.4PtSb, and Dy0.7Y0.3PtSb-with peak zT values exceeding 1.0. Notably, Dy0.7Y0.3PtSb achieves a maximum zT of 1.33 at 875 K. These findings underscore the promising potential of sublattice-softened RE-HHs as highly efficient thermoelectrics with broad compositional tunability.

Efficient heat dissipation is vital for the reliability and performance of next-generation nanoelectronics based on two-dimensional MA2Z4 (M = Mo, W, V, Nb, Ta, Ti, Zr, Hf or Cr, A = Si, Ge, and Z = N, P, As) semiconductors. While their electronic and mechanical properties have been extensively characterized, the microscopic physics governing thermal transport in these complex septuple-atomic-layer structures remains elusive. In this work, we systematically investigate the intrinsic lattice thermal conductivity of monolayer CrSi2N4 by developing machine-learned potentials trained on first-principles data. This framework captures many-body interatomic interactions with quantum-mechanical accuracy, enabling rigorous assessment of phonon dynamics via large-scale molecular and lattice dynamics calculations. We predict a high room-temperature thermal conductivity of approximately 372 W m-1 K-1 for CrSi2N4, positioning it as a promising heat-spreading candidate. Mode-resolved analyses reveal that heat transport is dominated by in-plane acoustic phonons; the flexural modes undergo pronounced anharmonic renormalization, significantly suppressing their contribution to total heat flux. Compared with MoSi2N4, the disparity in thermal conductivity of CrSi2N4 originates from altered lattice anharmonicity and a constricted three-phonon scattering phase space rather than atomic mass effects. These results provide insight into phonon transport in Cr-based MA2Z4 nitrides and demonstrate the effectiveness of machine-learned potentials for predicting thermophysical properties of complex two-dimensional materials.

Tuning thermal conductivity (κ) of metal-organic frameworks (MOFs) is pivotal for advancing their emerging thermoelectric applications and addressing the heat dissipation bottleneck in gas adsorption processes, yet heat conduction mechanisms in MOFs, particularly from the perspective of intrinsic lattice vibrations, remain elusive, limiting rational thermal engineering. Here, we focus on organic ligand rotational dynamics and elucidate their critical but long-overlooked modulations on thermal transport. Through elaborate atomistic simulations on prototypical MIL-47, we report that low-frequency, anharmonic linker librations dramatically intensify phonon scattering, inducing an over 2-fold reduction in κ. Such a suppression effect is further confirmed to be universal across diverse flexible frameworks featuring rotatable ligands, including the known zeolitic imidazolate and covalent organic families. Accordingly, we evaluate multiple practical strategies to regulate κ by tailoring linker rotational dynamics. These insights open vast avenues for the flexible design of MOFs' thermal performance to meet their energy-related applications.

Phonon softening and in-plane anisotropy in KFeS2 nanoribbons: a Raman spectroscopy investigation.

Phonons, quantized vibrations of the atomic lattice, are central to thermal transport, structural stability, and phase behavior in crystalline solids. However, most large-scale materials databases rely on the harmonic approximation and neglect important temperature-dependent anharmonic effects. Here, we present a scalable framework combining machine learning interatomic potentials, anharmonic lattice dynamics, and high-throughput calculations to predict finite-temperature phonons across thousands of materials. By fine-tuning the universal M3GNet potential with high-quality phonon data, we improve phonon prediction accuracy fourfold while retaining computational efficiency. We integrate this refined model with a high-throughput implementation of the stochastic self-consistent harmonic approximation to compute temperature-dependent phonons for 4669 inorganic compounds. The resulting dataset reveals systematic elemental and structural trends in anharmonic phonon renormalization, especially in alkali metals, perovskite-derived frameworks, and related systems. Machine learning analysis identifies weak bonding, large atomic radii, and specific coordination motifs as key drivers of strong anharmonicity. First-principles validation further shows that anharmonic effects can change lattice thermal conductivity by factors of two to four. This work provides an efficient data-driven platform for predicting finite-temperature phonon behavior and guiding the discovery of materials with tailored thermal and vibrationalproperties.

We report a complete neutron-scattering and molecular dynamics investigation of the structure and dynamics of monomer and polymer phases of C60 carbon peapods. Above ∼250 K, the physics of the confined chains can fully be described without accounting for the nanotube, the latter merely playing the role of a container for a 1D system─the system can be described as an unpinned state in the extended Frenkel-Kontorova framework. As the temperature is lowered below about 250 K, we observe a progressive damping of the longitudinal acoustic phonons, measured in both monomer and polymer data. As a set of experimental observations suggest that this damping can be attributed neither to a 3D ordering of the chains nor to a transition driven by rotation-rotation-translation coupling, we attribute it to an increase in the chain-nanotube interaction. This translates into a progressive pinning of the C60 chains on the nanotube lattice as the temperature is lowered and explains the observed low-temperature damping.

The origin of superconductivity in oxide interfaces and its relation to ferroelectricity remains an open question. At LaAlO3/SrTiO3 interfaces, quantum confinement and inversion symmetry breaking create a two-dimensional electron gas near a ferroelectric quantum critical point, yet direct evidence linking phonon dynamics to electron pairing has been lacking. Here we directly probe lattice vibrations and atomic structure at LaAlO3/SrTiO3 interfaces across the superconducting phase diagram using vibrational spectroscopy with momentum selectivity in a scanning transmission electron microscope. We find that superconductivity across the doping series correlates with inversion symmetry breaking and the appearance of high-frequency localized phonons. These tunable, polar vibrations-confined near the interface-exhibit strong electron-phonon coupling and evolve systematically with carrier density. Our findings establish a link between lattice instability, superconductivity and strong electron-phonon coupling mediated by tunable localized phonons, providing new insights into possible microscopic pairing pathways in quantum paraelectric systems.

The phenomenon of intriguing Rashba spin splitting, which is driven by intrinsic structural symmetry breaking and spin-orbit coupling (SOC), has been observed in various perovskite materials. However, it remains unclear how phonon vibrational frequency affects spin carrier dynamics in two-dimensional perovskites exhibiting the Rashba effect. A thorough exploration of the electronic structures and the mechanism behind the strain-induced lattice vibration on spin dynamics in Ruddlesden-Popper (RP) Cs2GeI2Cl2/InSe heterostructure is presented herein, based on nonadiabatic molecular dynamics (NAMD) simulations with spin-orbit coupling (SOC) and density functional theory. Remarkably, the bandgap magnitudes and the extent of spin splitting within the Cs2GeI2Cl2/InSe heterostructure has been significantly increased under compressive strain (ε = -4%). This enhancement is attributed to the decrease of the in-plane Ge-Cl bond length, which results in stronger Coulomb interaction and increased distortion of the [GeI2Cl4]4- octahedral. When applying compressive strain on the heterostructure, more high frequency phonons (200-1000 cm-1) participate in carrier relaxation process, leading to ultrafast spin dynamics (310.01 fs). The frozen phonons NAMD results show that high-frequency phonons promote carrier transfer more than low-frequency phonons in the 2D perovskite-based heterostructure. Interestingly, the Rashba spin dynamics also can be manipulated by the temperature, revealing that the phonon vibrational frequency is temperature-dependent. These findings highlight the importance of high-frequency phonons on Rashba spin dynamics in perovskite-based photoelectronic devices.

We provide a framework to theoretically describe long-range energy transfer in single and twisted two-dimensional hyperbolic slabs. We demonstrate that phonon polaritons, quantum superpositions of photons and lattice vibrations in polar dielectrics, can mediate and enhance energy transfer at ranges far exceeding those of conventional mid-infrared (MIR) platforms and with extreme directionality. This is because the dipole-dipole interaction potential energy diverges along the asymptotes of the real-space hyperbolic opening angle. Our findings allow us to extend classical and quantum interactions between dipoles, typically strictly confined to the near-field, beyond several free-space MIR wavelengths. We use α-MoO3 as a representative material, but this mechanism could be extended to other anisotropic media beyond the MIR.

We argue that the Jahn-Teller (JT) phonon manifold responsible for superconductivity in alkali-doped fullerides A3C60 supports circular, chiral combinations in a symmetry-adapted basis, and that this perspective gives a clean group-theoretical account of why these materials are robust s-wave superconductors. Embedding the fivefold Hg irrep in the l = 2 parent representation of SO(3), we use Clebsch-Gordan algebra in the circular basis to obtain the channel weights W(q) = 3/5 for all q ∈ {-2,-1, 0, +1, +2}. The chiral channels (q ̸= 0) carry 80% of the total coupling weight, the achiral channel (q = 0) the remaining 20%, but the central robust result is the equality between opposite chiral sectors, W(+m) = W(-m), enforced by time-reversal symmetry. The angular-momentum-weighted contribution of the chiral channels cancels identically, so the Cooper pair carries zero net angular momentum in any time-reversal-symmetric environment. A McMillan calculation reproduces the experimental Tc = 19.3 K of K3C60, and the same calculation reveals that the s-wave channel is parametrically robust against any equilibrium time-reversal-breaking perturbation because μBB ≪ ωph for the stiff intramolecular Hg modes. In two-dimensional
systems with soft acoustic phonons and strong effective time-reversal breaking-most notably the chiral superconductor in valley-polarized rhombohedral trilayer graphene (RTG)-the same symmetry analysis allows a chiral p-wave channel, placing fullerides and RTG as two limits of a single mechanism controlled by the dimensionless ratio δε/ωph. We provide an order-of-magnitude estimate of mode-resolved phonon Zeeman splittings as a possible experimental signature, while emphasizing that a quantitative prediction requires a microscopic calculation of the orbit-lattice coupling.

La3- xTe4 materials are ideal candidates for next-generation radioisotope thermoelectric generators due to their excellent thermoelectric performance and high-temperature stability. For decades, researchers have used substitutional doping or vacancy modulation to tune carrier concentration, but these methods can only tune it without optimizing the conduction band structure or suppressing lattice thermal conductivity. Interstitial doping strategy breaks this deadlock by enabling simultaneous electronic and thermal regulation without mutual interference. Herein, a series of Cu-doped La2.74CuxTe4 (x = 0, 0.01, 0.05, 0.1, 0.15) samples were synthesized. Cu incorporation elevates the Seebeck coefficient without degrading significantly the power factor, while simultaneously suppressing lattice thermal conductivity via anharmonic vibrational behavior that strengthens low-frequency acoustic phonon modes and intensifies phonon-phonon scattering. Among the synthesized compositions, La2.74Cu0.05Te4 achieves a peak thermoelectric figure of merit of 1.58 at 1073 K, representing a 34% improvement over the undoped La2.74Te4. Furthermore, the material exhibits a notable average zT value of 1.5 within the operational temperature range of 873-1073 K. When compared to the previously reported state-of-the-art lanthanum telluride-based thermoelectrics, this represents a significant improvement of 71.3% in the average zT value.

A highly efficient and interpretable framework for high-precision lithological identification integrating SERS and XGBoost.

Anisotropic thermal expansion and low-frequency vibrational modes in galactitol: Insights from temperature-dependent terahertz spectroscopy and density functional theory calculations.

Lanthanide-driven lattice softening provides an integrated framework to couple electronic transport, phonon dynamics, and surface reaction kinetics in β-Ag2Se. First-principles calculations reveal that La and Gd incorporation induces a near-metallic electronic structure, where dopant d/f states hybridize with Se p orbitals to generate a continuous density of states at the Fermi level, enhancing carrier delocalization and electrical transport. This electronic reorganization weakens lattice restoring forces, reducing the bulk modulus from ∼77 GPa in pristine Ag2Se to ∼23 GPa in LaAg2Se before partially recovering to ∼52 GPa in GdAg2Se. The softened lattice exhibits low-frequency acoustic phonon behavior and increased polarizability, indicative of stronger electron-phonon coupling and modified thermoelectric transport characteristics. Such vibrational flexibility simultaneously facilitates CO2 activation. Climbing-image nudged elastic band calculations show a significant reduction in the *COOH formation barrier in doped systems, arising from cooperative lattice relaxation and metallic electron donation that stabilize the transition state. Despite elastic softening, positive stiffness eigenvalues and controlled elastic anisotropy confirm mechanical stability. The coexistence of metallic conductivity, lattice polarizability, and soft phonon modes enables dynamic adsorbate accommodation while preserving transport functionality. These findings establish lanthanide-modified β-Ag2Se as a transport-coupled platform in which lattice softness, carrier density, and phonon engineering jointly govern thermoelectric behavior and catalytic reactivity.

Electron Ptychography is a computational imaging technique capable of performing phase retrieval at atomic resolution. Here we introduce the CAVIAR framework (Correlated Atomic Vibration Imaging with sub-Angstrom Resolution) that reveals spatial correlations in atomic displacements at the atomic scale. Using realistically simulated data for a symmetric Σ9 grain boundary in silicon and experimental data of a hexagonal boron nitride bicrystal, we observe correlations between atomic movements in the range of 10-20 pm at room temperature in agreement with our expectation. From only the atomic masses and temperature as input, we obtain frequencies of the longitudinal and transverse acoustic and optic phonons from just a few nm3 volume, in agreement with inelastic neutron scattering. This ability to spatially resolve correlated atomic motion distinguishes CAVIAR and positions it as a complementary tool to vibrational electron energy loss spectroscopy for exploring atom dynamics at the finest scale.

Lattice defects in crystalline materials play a critical role in tuning thermal transport, as their thermal properties are highly sensitive to the atomic structure. However, characterizing such structure-property relationships has been hampered by the challenges in directly measuring thermal properties at the single-defect level. Here, we employ in situ scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) to characterize ripplocation boundary-like defects (RBDs, i.e., curved lattice boundaries) in graphite, revealing their atomic-scale lattice dynamics and quantifying their local thermal resistance. At the RBD cores, we observe distinct spectral broadening of the out-of-plane and transverse acoustic phonon modes, a signature of enhanced localized phonon scattering. In situ STEM-EELS measurements reveal that the local thermal resistance of the RBDs is approximately 3-5 times higher than that of the defect-free matrix. Specifically, the typical thermal resistance of individual RBDs ranges from 4.69 × 10-11 to 8.06 × 10-11 m2·K·W-1, exhibiting dependence on the bending angle. These findings establish a quantitative link between the RBD atomic configurations, phonon features, and thermal resistance, providing guidelines for defect-engineered thermal management of graphite-based materials.

Understanding vibrational lifetimes at surfaces is central to advancing our knowledge of thermal transport, energy dissipation, and nanoscale friction. While phonon lifetimes in the bulk are routinely accessed via inelastic neutron scattering or optical phonon modes via high-resolution Raman spectroscopy, the direct measurement of lifetimes for low-energy surface acoustic phonons, particularly at finite wavevector, remains a major experimental challenge. This is due to the extremely narrow linewidths involved, corresponding to picosecond lifetimes and requiring µeV energy resolution. Here, we demonstrate how helium spin-echo (HeSE) spectroscopy overcomes this limitation, enabling direct access to the intrinsic linewidths and lifetimes of surface vibrational modes. For Ag(001), we map the full dispersion of the Rayleigh wave. Temperature-dependent measurements at finite wavevector reveal its weak anharmonicity and allow extraction of its intrinsic linewidth from the associated broadening. This corresponds to a phonon lifetime of ≈29 ps at 0 K and a propagation length of ≈44 nm, indicating coherence over tens of nanometres despite electron–phonon and defect-induced scattering. In a complementary application, we explore the vibrational dynamics of organic adsorbates, using cobalt phthalocyanine (CoPc) on Ag(001) as a model system. Low-frequency frustrated translational modes of the adsorbed molecules illustrate HeSE’s capability to probe vibrational damping in complex adsorbate–surface systems. The observed linewidths reflect enhanced dissipation arising from intermolecular interactions and coupling to the substrate. These findings establish HeSE as a sensitive probe of vibrational energy dissipation at hybrid organic–metal interfaces. Taken together, these capabilities open new avenues for the quantitative study of phonon lifetimes and linewidths in complex and emergent material systems, including 2D heterostructures and unconventional superconductors, where vibrational dynamics and their coupling to other degrees of freedom play a decisive role.

Controlling ferroelectric polarization with light promises a frontier for ultrafast optoelectronics. Yet the fundamental mechanism by which transient photoexcitation produces persistent photocurrent retention has remained elusive. Here we demonstrate a quasiparticle state that mediates photoferroic retention in the van der Waals ferroelectric CuInP2S6. We identify ferrons, collective excitations of dipole-carrying lattice vibrations, as carriers of optically imprinted polarization states. Narrowband resonant ferron oscillations at 2.16 THz exhibit a butterfly-shaped hysteresis that mirrors the photocurrent hysteresis response, directly linking ferron dynamics to polarization-dependent photocurrent retention at room temperature. Above-bandgap photoexcitation drives ferron formation through displacive excitation of coherent lattice motion, enabling carrier-mediated reconfiguration of ferroelectric domains, while sub-bandgap excitation leaves the polarization unaltered. The analytical calculations quantitatively capture the symmetry-dependent photocurrent generation and the consequence of the ferron-mediated hysteresis. These results establish ferronics, the manipulation of ferroelectric order through ferronquasiparticles, as a distinct paradigm for optically controlled polarization and photocurrent retention in low-dimensional quantum materials.

A sealed-vessel approach produced high-purity wurtzite hexagonal ZnO nanorods (P63mc, JCPDS 00-36-1451) with an exceptionally rapid holding duration of 50 s at 150 °C, utilizing microwave radiation from a Monowave 400 reactor. The process is more rapid than prior microwave methods, which require 2-7 min, and is significantly quicker than hydrothermal and sol-gel techniques that take hours to days, utilizing less than 10 Wh of energy compared to the energy-intensive hydrothermal method (energy savings exceeding 95%). The XRD study indicated a Scherrer crystallite size of 25.22 nm, a crystallinity of 48.5%, and a microstrain, as per the Williamson-Hall equation, of ε × 103 = 3.39. The results are consistent with a highly organized hexagonal wurtzite structure characterized by cell parameters a = b = 3.2494 Å and c = 5.2066 Å. A TEM study of 100 nanorods revealed a uniform morphology with an average diameter of 22.4 ± 3.2 nm, a length of 185 ± 25 nm, and an aspect ratio of 8.3 ± 1.4, indicating preferential development along the c-axis attributable to microwave coupling. The UV-Vis spectrophotometer yielded a cutoff absorption wavelength of λ = 374 nm, which corresponds to a band gap energy of 3.318 eV. The Fourier transformed infrared (FTIR) spectra validated the lattice vibrations of Zn-O bonds at 436 and 630 cm-1. Energy dispersive X-ray (EDX) revealed a near-stoichiometric composition (Zn = 51.48% and O = 48.52%), with no detected contaminants.

Transient non-equilibrium thermal transport in silicon-based FinFET