We demonstrate quantum levitation controlled by Casimir forces acting between a polystyrene surface and a Teflon-coated metallic substrate immersed in a mixture of toluene and magnetite particles. This system experiences repulsion-attraction transitions in the Casimir interaction for distances where the effect is measurable. This Casimir trapping can be controlled by clever choices of metallic and ferrofluid materials, which are directly linked to the emergence of the trapping effect. Thermal and quantum contributions are investigated in detail, showing how the optical and magnetic properties of the ferrofluid and other materials affect the magnitude of the trapping and its distance range of observability.

We perform $\mathit{in} \mathit{situ}$ angle-resolved photoemission spectroscopy to investigate the effect of surface termination conversion on two-dimensional electron gas (2DEG) at the ${\mathrm{EuTiO}}_3$(001) surface. We successfully engineered ${\mathrm{EuTiO}}_3$ with nearly single ${\mathrm{TiO}}_2$ termination via epitaxial growth on ${\mathrm{TiO}}_2$-terminated ${\mathrm{SrTiO}}_3$, and ${\mathrm{EuTiO}}_3$ with nearly complete EuO termination by inserting a ${\mathrm{SrRuO}}_3$ buffer layer into the heterostructure. The orbital configuration of the 2DEG exhibits a strong dependence on the ${\mathrm{EuTiO}}_3$ termination, and this experimental observation matches our first-principles calculation results very well. Furthermore, we observe the termination dependence of a kink feature in $d_{xy}$ band. This finding implies that many-body interactions, and possibly magnetism, are influenced by the surface termination. Our study not only introduces a method to fabricate surface or interfacial 2DEG system, but also highlights the effect of termination conversion on magnetic 2DEG.

For large polarons, Fröhlich theoretically derived an increased effective mass and a decreased energy as compared to free charge carriers. These changes have hitherto eluded direct observation. Here, we report on the direct observation of large polaron formation after photoexcitation in BiOI nanoplatelets, a system known to host spatially separated e-h pairs. We employ time- and momentum-resolved photoemission electron microscopy with 50-fs pulses to monitor the dynamics of the conduction-band (CB) dispersion $E\left(k\right)$. Indeed, we observe a doubling of the effective mass accompanied by a decrease of the CB energy leading to an overall drop of 160 meV.

In this work, we report on large-scale molecular-dynamics (MD) simulations of displacement cascades in equiatomic NbMoTaW alloys at PKA energies ranging from 0.15 to 150 keV. We find defect production to be strongly dependent on recoil energy, scaling sublinearly up to 10 keV, and linearly thereafter. We find the sublinear regime to be defined by low values of surviving Frenkel pairs, typically found as isolated point defects or small defect clusters, while at higher recoil energies dense cascades become more frequent, leading to splitting into subcascades and the production of relatively large prismatic-dislocation loops with $\langle 111\rangle$ and $\langle 001\rangle$ Burgers vectors. These loops immobilize large fractions of defects, leading to a rapid growth of the number of surviving defects in the linear regime. We also anneal post-cascade defect configurations using object-kinetic Monte Carlo (OKMC) simulations to account for intracascade recombination on time scales not accessible to MD simulations. Cascade annealing is strongly temperature dependent, with the OKMC simulations only showing significant recovery at 1000 K but not below. Our results are in general agreement with existing published data for refractory concentrated alloys.

We develop a machine-learned interatomic potential for AlCrCuFeNi high-entropy alloys (HEA) using a diverse set of structures from density functional theory calculated including magnetic effects. The potential is based on the computationally efficient tabulated version of the Gaussian approximation potential method (tabGAP) and is a general-purpose model for molecular dynamics simulation of the HEA system, with additional emphasis on radiation damage effects. We use the potential to study key properties of AlCrCuFeNi HEAs at different compositions, focusing on the face-centered- and body-centered-cubic (fcc and bcc) phase stability. Monte Carlo swapping simulations are performed to understand the stability and segregation of the HEA and reveal clear FeCr and Cu segregation. Close to equiatomic composition, a transition from fcc to bcc is detected, following the valence electron concentration stability rule. Furthermore, we perform overlapping cascade simulations to investigate radiation damage production and tolerance. Different alloy compositions show significant differences in defect concentrations, and all alloy compositions show enrichment of some elements in or around defects. We find that, generally, a lower Al content corresponds to lower defect concentrations during irradiation. Furthermore, clear short-range ordering is observed as a consequence of continued irradiation.

Rare earth (RE)–free permanent magnets, as alternative substitutes for RE-containing magnets for sustainable energy technologies and modern electronics, have attracted considerable interest. We performed a comprehensive search for new hard magnetic materials in the ternary Fe-Co-Zr space by leveraging a scalable, machine learning–assisted materials discovery framework running on GPU-enabled exascale computing resources. This framework integrates a crystal graph convolutional neural network (CGCNN) machine learning (ML) method with first-principles calculations to efficiently navigate the vast composition-structure space. The efficiency and accuracy of the ML approach enable us to reveal 9 new thermodynamically stable ternary Fe-Co-Zr compounds and 81 promising low-energy metastable phases with their formation energies within 0.1 eV/atom above the convex hull. The predicted compounds span a wide range of crystal symmetries and magnetic behaviors, providing a rich platform for tuning functional properties. Based on the analysis of site-specific magnetic properties, we show that the ${\mathrm{Fe}}_6{\mathrm{Co}}_{17}{\mathrm{Zr}}_6$ compound obtained from our ML discovery can be further optimized by chemical doping. Chemical substitutions lead to a ternary ${\mathrm{Fe}}_5{\mathrm{Co}}_{18}{\mathrm{Zr}}_6$ phase with a strong anisotropy of ${\mathrm{K}}_1=1.1\mathrm{MJ}\text{/}{\mathrm{m}}^3$ and a stable quaternary magnetic ${\mathrm{Fe}}_5{\mathrm{Co}}_{16}{\mathrm{Zr}}_6{\mathrm{Mn}}_4$ compound.

The interlayer exchange coupling in Fe/MgO(001) superlattices is found to increase exponentially with decreasing temperature. Around 150 K, the field-induced response changes from discrete switching—governed by field-driven domain propagation—to a collective rotation of the magnetic layers. This transition is accompanied by a change in the magnetic ground state from ${180}^{\circ }$ (antiferromagnetic) to ${90}^{\circ }$ alignment between adjacent Fe layers. These effects are argued to arise from quantum-well states, defined by the total thickness of the samples.

The anomalous Nernst effect (ANE), a thermoelectric (TE) phenomenon that generates a voltage perpendicular to both temperature gradients and spontaneous magnetization, has attracted interest in energy harvesting applications. However, its practical implementation remains limited by low TE conversion efficiency. Here, we investigated strain-induced enhancement of ANE in a $\mathrm{D}{0}_3$-type Heusler compound $\mathrm{F}{\mathrm{e}}_3\mathrm{Si}$ using first-principles calculations. The transverse TE conductivity improved approximately 50-fold compared to the unstrained condition, due to the $4\%$ compressive strain loading on the (111) plane. The electronic structure analysis revealed that the improvement stems from the nodal line shift closer to the Fermi energy under compressed strain. Strain engineering offers a promising approach to manipulate the topological electronic structure, such as nodal lines and Weyl nodes, which are the origin of ANE, and thus enhance TE performance. These results suggest new design principles for high-performance TE devices.

Currently, the realization and control of anomalous valley Hall effect (AVHE) in two-dimensional antiferromagnetic (AFM) systems are predominantly achieved through optical excitation, which hinders its practical applications. Here, we propose a strategy to overcome this limitation by inserting a valley-active AFM layer between two ferromagnetic (FM) semiconductor layers. Using $\mathrm{Cr}{\mathrm{Cl}}_3-\mathrm{VSi}{\mathrm{S}}_3-\mathrm{Cr}{\mathrm{Cl}}_3$ heterotrilayer as a model system, our first-principles calculations reveal that interfacial proximity coupling can introduce intrinsic sublattice-asymmetric exchange field. This field can break the $\mathit{PT}$ symmetry and lift the spin degeneracy of valleys in the AFM layer while preserving its intrinsic valley polarization, thereby inducing a pronounced AVHE. Crucially, the sublattice-asymmetric exchange field can be reversed through flipping the magnetization orientation of the FM layers, resulting in reversible static control of AVHE without altering the AFM Néel order. These findings establish an alternative paradigm for controlling AVHE in AFM materials and advance the field of antiferromagnet-based valleytronics.

Quasi-one-dimensional GaSeI nanochain with a noncentrosymmetric helical chain structure have recently been synthesized, offering a unique platform for exploring mechanical and thermal properties in low-dimensional materials. Here, we develop a neuroevolution potential (NEP) for GaSeI nanochain based on ab initio molecular-dynamics (AIMD) simulations, enabling systematic investigation of their mechanical response and lattice thermal transport. Stress-strain analysis reveals that GaSeI nanochain exhibits mechanical strength comparable to carbon nanotubes, with ultimate stress approaching that of graphene, indicating that, despite distinct bonding mechanisms, the material possesses high structural stability. Nonequilibrium molecular-dynamics (NEMD) calculations show that the lattice thermal conductivity is lower than that predicted by the phonon Boltzmann transport equation, due to the inherent inclusion of higher-order phonon scattering in NEMD. Thermal conductivity decreases modestly with increasing tensile strain, yet the reduction is far smaller than that observed in typical one-dimensional materials, such as carbon nanotube. This behavior arises from the weaker polar-covalent nature of Ga-Se bonds, which can buffer structural perturbations via local bond-angle adjustments, thereby maintaining robust phonon transport. These findings demonstrate that GaSeI nanochain possess both excellent mechanical stability and strain-insensitive thermal conductivity, suggesting their potential application in thermal management of flexible, stretchable, and deformable devices.

The checkerboard lattice has been proposed to host topological flat bands as a result of destructive interference among its various electronic hopping terms. However, it has proven challenging to realize experimentally due to the difficulty of isolating this structure from any significant out-of-plane bonding while maintaining structural integrity. Here, single crystals of ${\mathrm{Zr}}_2{\mathrm{CuSb}}_3$, a potential candidate for the checkerboard lattice, were synthesized using the solution (self-flux) method, and their structure was confirmed via x-ray diffraction. Electrical-transport measurements indicate metallic behavior with electron-dominated carriers. Angle-resolved photoemission spectroscopy reveals multiple electron pockets and significant $k_z$ broadening due to its large $c$ axis and low dispersion features in $k_z$. Density-functional theory (DFT) calculations further disentangle the contributions from each high-symmetry plane, providing a comprehensive characterization of electronic behavior. The DFT calculations were then used to determine the orbital contributions of the bands and detect the out-of-plane bonding which prevented the flat bands from forming.

Lanthanide fission products can strongly interact with candidate cladding alloys, but their transport properties in refractory metals remain poorly understood. In this work, we investigate the atomic-scale diffusion behavior of La, Ce, Pr, and Nd in body-centered cubic (bcc) molybdenum, a potential candidate for advanced nuclear cladding. Self-consistent mean-field transport modeling is performed to evaluate the fission product transport and vacancy mobility, informed by first-principles and nudged elastic band calculations of vacancy formation energies, migration barriers, and solute-vacancy binding characteristics. Compared with bcc Fe, lanthanide solutes in bcc Mo exhibit slower tracer diffusion due to higher vacancy formation and migration energies. Furthermore, the calculations reveal that the influence of fission products on migration barriers in bcc Mo are not as extensive in range compared to bcc Fe. Among the studied lanthanides, La exhibits the strongest vacancy binding while also being the fastest diffuser in Mo. These findings highlight how refractory bcc alloys can reduce fission product infiltration, offering valuable insight into the development of durable cladding systems for advanced reactors.

Recent advances in low-dimensional materials have revealed that one-dimensional (1D) monatomic chains serve as ideal platforms for exploring exotic quantum phases and emergent phenomena arising from spatial confinement. The synthesis of such structures within well-defined and stable templates represents a key step toward harnessing their unique physical properties. In this study, we utilize the naturally formed, spatially confined channels between self-assembled silicon nanoribbons (SiNRs) on a Si(111) surface as an ideal template for growing highly ordered potassium (K) monatomic chains. Using scanning tunneling microscopy and density functional theory (DFT) calculations, we systematically characterize the confined potassium (K) atoms by high aspect ratio SiNRs and the resulting electronic properties. Our results show that the unique confined space created by the SiNRs reduces the adsorption energy of K atoms by 0.09 eV. This reduction leads to preferential adsorption of K atoms between strands of double- and multistranded SiNRs, where they form a distinct triangular morphology with three neighboring Si atoms. This triangular structure is a result of charge transfer, as confirmed by our DFT calculations. At higher coverage, the K atoms self-assemble into 1D zigzag chain structures along the SiNRs. Notably, the adsorption of K atoms is reversible and can be precisely controlled by a scanning tunneling microscopy tip voltage pulse without causing damage to the SiNRs. Furthermore, the adsorption of K dynamically shifts the position of the Dirac cone relative to the Fermi level, offering an effective means of electronic tuning. This work not only elucidates the formation of artificial 1D K chains within the confined space of SiNRs, but also opens up avenues for the synthesis of atomically precise nanostructures through the use of special confined spaces.

Exciton mobility in two-dimensional semiconductors is a key ingredient in materials-based design of optoelectronic functionalities. Monolayer transition metal dichalcogenides (TMDs) set a good test case, with tightly bound excitons and designable flexibility that offer an ideal platform for realizing strain effects on exciton energy transfer. Here, we present an ab initio study to construct strain-induced exciton energy profiles and model exciton dynamics on top of these potential surfaces. We focus on spatially inhomogeneous strain in monolayer ${\mathrm{WS}}_2$, combining excitonic band structures derived from many-body perturbation theory for a large variety of strain profiles and calculate the change in mobility characteristics using a semiclassical ballistic transport model. We connect a wealth of strain patterns to exciton drift, diffusion, and confinement. Our findings point to strain-induced regimes of superballistic propagation and anomalous diffusion behavior, governed entirely by the strain landscape. Our results provide structure-specific understanding of ballistic strain-tunable exciton behavior, offering design principles for engineering exciton dynamics in two-dimensional materials.

Inorganic antiperovskite nitrides have recently emerged as promising materials for photovoltaic applications, yet their nonradiative recombination dynamics remain largely unexplored. Here, we examine the influence of X-site cation substitution on the nonradiative electron-hole recombination in ${\mathrm{X}}_3\mathrm{NSb}$ $(\mathrm{X}=\mathrm{Ca}, \mathrm{Sr}, \text{and} \mathrm{Ba})$. Ca- and Sr-based compounds adopt a cubic phase, whereas Ba stabilizes in a hexagonal structure, introducing pronounced symmetry-driven effects. To separate symmetry effects from cation chemistry, we also examine the hexagonal polymorph of ${\mathrm{Sr}}_3\mathrm{NSb}$ $\left({\mathrm{Sr}}_3{\mathrm{NSb}}_{\mathrm{hexa}}\right)$. Substituting Ca with Sr narrows the band gap, suppresses octahedral and band-edge fluctuations, reduces nonadiabatic (NA) coupling by $\sim 54\%$, and extends carrier lifetimes by a factor of 2.5. In ${\mathrm{Sr}}_3{\mathrm{NSb}}_{\mathrm{hexa}}$, the combination of larger band gap and enhanced band gap fluctuations—leading to faster dephasing—further slows down recombination by $41\%$. In contrast, in ${\mathrm{Ba}}_3{\mathrm{NSb}}_{\mathrm{hexa}}$, enhanced NA coupling accelerates recombination relative to ${\mathrm{Sr}}_3{\mathrm{NSb}}_{\mathrm{hexa}}$. Overall, recombination lifetimes are dictated by the interplay between band gap, NA coupling strength, and decoherence time, with ${\mathrm{Sr}}_3{\mathrm{NSb}}_{\mathrm{hexa}}$ exhibiting the longest lifetime. These findings highlight the coupled influence of cation chemistry and crystal symmetry in tailoring carrier dynamics for high-performance antiperovskite-based optoelectronics materials.

The Rashba-Edelstein effect (REE), which generates spin accumulation under an applied electric current, quantifies charge-to-spin conversion (CSC) efficiency in noncentrosymmetric systems. However, systematic investigations of REE in two-dimensional (2D) materials remain scarce. To address this gap, we perform a comprehensive symmetry analysis based on the 80 crystallographic layer groups, elucidating the relationship between materials' symmetries and the geometric characteristics of the REE response tensor. Our analysis identifies 13 distinct symmetry classes for the tensor and reveals all potential material candidates. Considering the requirement of strong spin-orbit coupling for a large REE response, we screen the C2DB database and identify 54 promising 2D materials. First-principles calculations demonstrate that the largest REE response coefficients in these materials exceed those reported for other 2D systems by an order of magnitude, indicating exceptionally high CSC efficiency. Focusing on three representative materials, including ${\mathrm{HgI}}_2, {\mathrm{AgTlP}}_2{\mathrm{Se}}_6$, and BrGaTe, we show that their large response coefficients can be well explained by effective $\mathit{k}·\mathit{p}$ models and the characteristic spin textures around high-symmetry points in momentum space. This work provides a systematic framework and identifies high-performance candidates, paving the way for future exploration of REE-driven CSC in 2D materials.

Recently, the real triple point characterized by Euler class in multigap systems, has been proposed beyond the conventional topological phase classifications. Here, we apply the subgroup lattice to study Euler topology and establish an explicit mapping between various undiscovered nodal line configurations (NLCs) evolving from the nontrivial real triple point and specific symmetry-breaking ways. Considering all symmetry-breaking paths from the magnetic point group $m$−$3m1$′ to −1′ with preserved $PT$ symmetry where $P$ and $T$ are inversion and time-reversal symmetries, respectively, 13 types of topological admissible NLCs are identified, with each subgroup exhibiting a one-to-one or one-to-two correspondence to them, which indicates an accurate design for a target nodal structure. In addition, through the analysis on the interplay between point-group symmetry and underlying non-Abelian topology, we promote an understanding on the formation mechanism of NLCs. Based on first-principles calculations, we verify the NLC evolutions in ten candidate phononic materials such as ${\mathrm{RbCaH}}_3$ and CuCl driven by external strain. The provided strain tensors to reach each corresponding subgroup can be a symmetry guidance for experimentally designing nodal line semimetals via strain engineering. Furthermore, we show that the optical conductivity purely induced by the quantum metric can serve as a nontrivial signature of distinct NLCs, and also can be manipulated along symmetry breaking. Our findings reveal the generality of realizing nodal structures characterized by the Euler class from a group-theoretical perspective that are applicable to real triple point materials in other systems.