Physical Review Materials

The authors have successfully induced and characterized a channel-like deformation mechanism in pure tungsten, providing a new experimental pathway to evaluate irradiation damage in future nuclear fusion reactors. While this phenomenon, where atomic layers slide rigidly like a solid cylinder being forced through a tight tube, is known to occur as a destructive byproduct of intense radiation inside fusion environments, it has previously been highly difficult to isolate and study in a controlled manner. In this work, they overcame this challenge by precisely pressing a microscopic tip into a specifically oriented tungsten single-crystal. Using advanced electron microscopy techniques, they studied the resulting atomic displacements and determined the channel-like deformation for the first time in this crystal structure. This opens a new avenue to study defect formation and propagation, critical for understanding fundamental plastic yielding and analyzing structurally identical irradiation-induced defects.

Co substitution in the kagome magnet TbFe${}_{6-x}$Co${}_x$Ge${}_6$ drives a remarkable evolution of both crystal structure and magnetic behavior. Through combined diffraction and magnetization studies, the series transitions from an ordered orthorhombic phase to a hexagonal Yb${}_{0.5}$Co${}_3$Ge${}_3$-type structure as Co content increases. The gradual disappearance of superstructure reflections reveals suppression of short-range structural order, while magnetic measurements demonstrate significant modification of transition-metal sublattice magnetism. These results establish chemical substitution as an effective route for tuning the interplay between structural ordering and magnetic interactions in rare-earth kagome materials, providing new insight into composition-driven phase evolution.

Symbolic regression tools like SISSO can model materials properties as compact analytical formulas depending on key physical parameters. In this contribution, a derivative-based sensitivity analysis is used to quantify how strongly each selected physical parameter drives a SISSO model’s predictions. Applied to the equilibrium lattice constant of perovskites, this approach pinpoints valence orbital radii, nuclear charges, and their products as the most important governing quantities. The partial-effects method offers a computationally efficient, physically intuitive alternative to techniques like SHAP for interpreting symbolic-regression models.

We investigate the spin Hall effect (SHE) in a van der Waals (vdW) ferromagnet Fe5GeTe2 (FGT) with a Curie temperature TC of 310 K utilizing the spin-torque ferromagnetic resonance method. The effective spin Hall conductivity is clearly enhanced with decreasing temperature, unlike the anomalous Hall conductivity, reflecting the variation in the band structure accompanied by the complicated magnetic ordering of the FGT. The results provide a deep understanding of the SHE in magnetic materials to open a new route for novel functionalities in vdW materials-based spintronic devices.

Why do relaxor ferroelectrics exhibit giant dielectric and piezoelectric responses over such a broad temperature range? By combining rapid-cooling synchrotron x-ray diffraction with neutron scattering, this work shows that phase transitions in PMN-xPT are remarkably sluggish and can even be bypassed by fast cooling. At the same time, the polar nanoregions display scale-free critical correlations in both space and time over the temperature range where the giant response appears. These results suggest that slow phase-transition kinetics sustain an extended critical state, providing a new physical picture for the origin of giant relaxor responses.

Machine-learning interatomic potentials now model complex alloys with near $ab$ $initio$ precision, but two challenges persist. Researchers must generate training data tailored to the physical process of interest, and they need validation metrics that go beyond simple statistical errors. Here the authors introduce a crystal-symmetry-based enumeration scheme for structural phase transformations in multicomponent alloys and a semi-grand-canonical Kendall-τ that quantifies thermodynamic accuracy across composition. These tools yield a general-purpose Mg-Nd potential. Simulations reveal a subtle interplay between chemical ordering and structural rearrangement and elucidate the continuous hcp-to-bcc transition underlying precipitation in this alloy.

The layered honeycomb antiferromagnets CrCl₃ and $\alpha$-RuCl₃ undergo similar first-order, temperature-driven layer-stacking rearrangements, yet respond remarkably differently to thermal cycling. CrCl₃ evolves smoothly through the transition and remains largely reversible, whereas $\alpha$-RuCl₃ shows an abrupt in-plane lattice discontinuity and accumulates structural disorder upon repeated cycling. Their magnetic correlations are also distinct, with diffuse magnetic scattering in CrCl₃ persisting to ~40 K, well above its ordering temperature, while no comparable quasi-static correlations are observed in $\alpha$-RuCl₃. These contrasts point to markedly different coupling between layer stacking, strain, and magnetism.

Magnetism sensitive only to the outermost atomic layer of a material is difficult to detect by x-rays. This is demonstrated using synchrotron x-ray scanning tunneling microscopy in spectroscopic mode, which simultaneously measures ensemble-averaged and surface-atomic-layer magnetism in an ultrathin Ni film. X-ray magnetic circular dichroism reveals an enhancement of orbital and spin magnetic moments in the outermost layer relative to the film average. This work opens a new experimental route for quantitative, element-specific magnetometry with atomic-layer sensitivity.

Amorphous halide solid‑state electrolytes have recently emerged as promising candidates for safe, high-energy‑density all‑solid‑state lithium batteries because of their high ionic conductivity and absence of grain boundaries. However, little is known about their mechanical properties, which are critical for suppressing lithium dendrite growth and ensuring manufacturability. Here we simulate for the first time the elastic behavior of the amorphous superionic conductor LiTaCl₆ (a prototypical amorphous halide) and show that molecular dynamics with machine‑learning force fields in the isothermal–isobaric ensemble (NPT MD) using a 2,000‑atom supercell yield a Young’s modulus in quantitative agreement with the experimental value.

Halide solid electrolytes such as Li₃YCl₆ and Li₃YBr₆ are promising candidates for safer, denser all-solid-state batteries, but their vast alloying space is hard to explore experimentally. Using the universal machine-learning potential PET-MAD, validated against a fine-tuned model, we map how halogen and metal substitution shape structure, phase stability and Li⁺ conductivity in Li₃MX₆ compounds. Halide mixing turns out to act through two competing levers: lattice contraction hinders Li motion, while shorter metal–halide bonds free up diffusion pathways, largely canceling out. Metal-site alloying, in contrast, tunes phase stability and cost with little penalty on conductivity: a practical design principle for optimizing these materials.

In this study, the authors investigate the real-time atomic dynamics and local structural fluctuations in GeTe by coupling density functional theory with large-scale molecular dynamics simulations driven by neuroevolution potentials. Their findings demonstrate a displacive ferroelectric phase transition near the tricritical point. Crucially, the computed longitudinal current correlation function lacks a quasielastic peak, effectively ruling out thermally activated discrete jumps. Furthermore, time-resolved orbital analyses reveal a femtosecond ‘seesaw’ charge transfer driven by the pseudo-Jahn-Teller effect. These results support a ‘macro-ordered yet micro-disordered’ displacive paradigm.

The stability of functional materials under operating conditions is of great importance in the search for materials with improved properties. This is in particular true for battery materials which have to operate robustly and safely under strongly varying electrochemical conditions. In this study, the authors demonstrate how a grand-canonical approach coupled to first-principles electronic structure calculations can predict the stability of chloride perovskites for Cl-ion batteries under operating conditions. This approach allows to determine whether the studied materials can be used as potential electrodes or solid-electrolytes or whether they are not appropriate for battery applications, thus contributing to an accelerated materials design.

Recent advances in protonic electrochemical random-access memory (ECRAM) have demonstrated ultrafast, nanosecond switching dynamics, seemingly faster than diffusion. We develop a theory to explain how these devices outperform some counterparts by up to five orders of magnitude by leveraging multiphase polarization in tungsten oxide, which can be tuned during annealing of the material. Supported by simulations, the theory shows that high-concentration metallic phases formed electrochemically along the gate enable the conductance to be modulated linearly and symmetrically throughout the ultrafast switching protocols.

Nitrogen-vacancy centers in diamond are widely used as quantum sensors, but creating shallow ensembles with high yield and reasonable spin coherence remains challenging. We show that high-angle nitrogen ion implantation efficiently forms shallow NV ensembles. Implanting ions at angles above 60° gives NV yields approaching 10% with effective depths below 10 nm. The oblique geometry enhances near-surface vacancy generation while keeping nitrogen close to the surface, improving the conditions for NV formation. The resulting ensembles retain stable charge states and useful spin coherence, offering a practical platform for nanoscale NMR and NQR sensing.

Nematicity in kagome metals $A$V${}_3$Sb${}_5$ ($A$ = K, Rb, Cs) has been widely regarded as an electronically driven phenomenon. Here, the authors uncover a structural origin of nematic behavior in the CDW phase of RbV${}_3$Sb${}_5$ through firstprinciples calculations. They show that an interlayer $\pi$ phase shift induces anisotropic V–V bond reconstruction, forming a bond-order wave that breaks C${}_6$ rotational symmetry and gives rise to intrinsic C${}_2$ anisotropy. This bond-order mechanism manifests in distinctive signatures across the electronic structure, Fermi surface, phonon spectrum, and transport properties, establishing a unified microscopic framework for lattice-driven nematicity in kagome quantum materials.

Excitation by linearly polarized femtosecond laser pulses provides a direct view into the altermagnetic structure via the non-equilibrium spin-polarized electronic populations in a band structure whose symmetry encodes the underlying bulk g-wave order. The spin-dependent electronic response calculated in this paper can be accessed by optical pump-probe experiments. The authors show that, surprisingly, such a purely optical technique reveals planar d-wave- and g-wave-like signatures hidden within the three-dimensional bulk g-wave spin-order configuration. Crucially, the symmetry properties of the calculated response can be well approximated by using two-dimensional “spin cuts”, which enable a transparent interpretation of the optical response and motivate concrete magneto-optical pump-probe configurations for bulk altermagnets.

Probing chirality below the diffraction limit is vital for understanding biological processes and designing chiral nanostructures. While orbital angular momentum (OAM)-resolved electron energy-loss spectroscopy (EELS) is a promising candidate for detecting nanoscale circular dichroism, experimental results remain elusive. This study presents a theoretical framework for understanding and optimizing the dichroic signal using a prototypical chiral nanostructure – a plasmonic nanohelix. By analyzing the role of various parameters, we demonstrate that the dichroism in EELS is sensitive to topological charge transfer, electron energy and sample geometry yet robust against minor experimental misalignments. These insights provide a roadmap for future nanoscale dichroism measurements.