Vacancy-Engineered Phonon Polaritons in a van der Waals Crystal

ACS Nano · 2026-05-15

≈ 0.13 within the lower Reststrahlen band. Stoichiometric analysis, density functional theory, and finite-difference time-domain simulations indicate vacancy concentrations of 1-2% and ≈-1.2% compressive strain, resulting in a dielectric permittivity modulation of up to ≈15%. Despite these structural perturbations, polariton lifetimes remain high (1.15 ± 0.29 ps). This work offers thermomechanical vacancy engineering as a robust route for reprogrammable polaritonic response in vdW crystals for nonvolatile nanophotonic architectures.

Investigating Electron Conductivity Regimes in the Bacterial Cytochrome Wire OmcS

The Journal of Physical Chemistry B · 2025-11-08 · 2 citations

produces extracellular, electronically conductive cytochrome polymer wires that are conductive over micron length scales. Structure models from cryo-electron microscopy data show OmcS wires form a linear chain of hemes along the protein wire axis, which is proposed as the structural basis supporting their electronic properties. However, the mechanism by which this heme arrangement supports long-range electronic conduction remains unknown. Structure models from cryo-electron microscopy data show these wires form a linear chain of hemes along the protein wire axis, which is proposed as the structural basis supporting their electronic properties. Existing computational models using static heme redox potentials and coupling energies fail to explain experimental observations, predicting conductances 10,000 to 100,000 times lower than measured values. Here, we investigate how dynamic disorder affects site energies, interheme coupling, and long-range electronic conductivity within these cytochrome wires. We introduce an approach to extract charge carrier site information directly from Kohn-Sham density functional theory, without employing projector schemes, and show that site and coupling energies are highly sensitive to changes in interheme geometry and the surrounding electrostatic environment. Unlike models that incorporate dynamic disorder as a thermally averaged quantity, our quantum charge carrier model incorporates proxies for dynamic disorder through decoherence corrections, yielding predicted diffusion coefficient closer to what is expected from experiment and comparable with other organic-based electronic materials. Based on these simulations, we propose that the instantaneous fluctuations of the local electrostatic environment can transiently lift energy degeneracies and delocalize charge carriers. These studies reveal how incorporating dynamic fluctuations associated with the environment resolves the discrepancy between theory and experiment in microbial cytochrome wires and highlight design principles for bioinspired, heme-based conductive materials.

Role of crystal field distortions in the charge density wave transition of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Ta</mml:mi><mml:msub><mml:mi mathvariant="normal">S</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Physical review. B./Physical review. B · 2025-05-28 · 1 citations

Research on charge density waves (CDWs) in 2D transition-metal dichalcogenides like $\mathrm{Ta}{\mathrm{S}}_{2}$ has predominantly focused on acoustic mode softening, largely overlooking the impact of crystal field effects (CFEs). This oversight has neglected crucial phenomena such as the formation of a flat band and the roles of flat bands in metal--insulator transitions. Our study shows that CFEs are essential for the formation of flat bands, the stability of the CDW phase, and the accompanying metal--insulator transition. These findings provide pivotal insights and pave the way for rational manipulation of CDW phases in 2D materials, offering substantial benefits for practical applications.

Dimensionally resolved nanostructures of an atomically precise and optically active 1D van der Waals helix

ChemRxiv · 2025-06-10 · 1 citations

Inorganic freestanding helices are rare and are sought-after for their unusual physical states endowed by chirality. To this end, III-VI-VII solids have emerged as a distinct class of ternary 1D van der Waals (vdW) crystals which bear atomically precise helical motifs. However, the physical understanding of the instrinsic and size-dependent properties of these materials is limited by the lack of synthetic strategies to directly access freestanding nanocrystals in high volumes. Using GaSI as a representative phase, we present a bottom-up strategy to grow high yields of ultrathin nanostructures based on this helical materials class. With this strategy, we were able to grow single crystals of 1D nanowires with thicknesess in the 10 to 100 nm range at high temperature conditions, as well as quasi-2D nanoribbons at lower temperatures. We establish the band gap of the nanowires in the UV region and demonstrate the persistence of nonlinear optical behavior originating from the non-centrosymmetric crystal structure of GaSI. Inspired by these results, we probe the effect of chirality on the electronic structure of hypothetical single chains of GaSI from first principles and show the pronounced handedness-dependent and chirality-driven spin polarization at the single helix regime.

Unveiling the Atomic Vibrational Anisotropy and Electron-Phonon Coupling via Momentum-Selective Electron Microscopy

Microscopy and Microanalysis · 2025-07-01 · 1 citations

Resolving Vibrational Modes at the FeSe/SrTiO3 Interface with Atomic-Scale Momentum-Selective Dark-Field EELS

Microscopy and Microanalysis · 2025-07-01

Magnetic Anisotropy in 2D van der Waals Magnetic Materials and their Heterostructures: Importance, Mechanisms, and Opportunities

Advanced Functional Materials · 2025-08-05 · 12 citations

Abstract 2D magnetism in atomically thin van der Waals (vdW) monolayers and heterostructures has attracted significant attention due to its promising potential for next‐generation spintronic and quantum technologies. A key factor in stabilizing long‐range magnetic order in these systems is magnetic anisotropy, which plays a crucial role in overcoming the limitations imposed by the Mermin‐Wagner theorem. This review provides a comprehensive theoretical and experimental overview of the importance of magnetic anisotropy in enabling intrinsic 2D magnetism and shaping the electronic, magnetic, and topological properties of 2D vdW materials. It begins by summarizing the fundamental mechanisms that determine magnetic anisotropy, emphasizing the contributions from strong ligand spin–orbit coupling of ligand atoms and unquenched orbital magnetic moments. A range of material engineering approaches is then examined, including alloying, doping, electrostatic gating, strain, and pressure, that have been employed to effectively tune magnetic anisotropy in these materials. Finally, open challenges and promising future directions in this rapidly advancing field are discussed. By presenting a broad perspective on the role of magnetic anisotropy in 2D magnetism, this review aims to stimulate ongoing efforts and new ideas toward the realization of robust, room‐temperature applications based on 2D vdW magnetic materials and their heterostructures.

Magnetic transition of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>LaMn</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math> films caused by symmetry restoration

Physical review. B./Physical review. B · 2025-04-28

The bulk $\mathrm{LaMn}{\mathrm{O}}_{3}$ (LMO) is antiferromagnetic (AFM) at low temperature, whereas its thin films growing on $\mathrm{SrTi}{\mathrm{O}}_{3}$ (STO) substrates are ferromagnetic (FM) in experiments. The underlying mechanism driving this AFM\ensuremath{\rightarrow}FM transition remains elusive and has attracted significant research interest. In bulk LMO, the $\mathrm{Mn}{\mathrm{O}}_{6}$ octahedra exhibit substantial crystal-field distortion. Our study reveals that the lattice mismatch between LMO films and STO substrates induces this magnetic phase transition in the ultrathin regime. The epitaxial strain effectively suppresses the octahedral distortion in LMO, leading to near degeneracy of the two Mn ${e}_{g}$ orbitals. This alteration in orbital energy splitting modifies the exchange interactions, thereby changing the magnetic ordering. Test calculations with varying octahedral symmetry by strains reproduced the AFM\ensuremath{\leftarrow}FM transition in LMO films, demonstrating a close correlation between the energy splitting between the two Mn ${e}_{g}$ orbitals and magnetic order in LMO. Based on these findings, we propose a superexchange mechanism driven by orbital degeneracy, offering a straightforward explanation for the magnetic transition in LMO films.

Filters, algorithms, and the “imagination tax”: the dilemma of aesthetic self-objectification among Chinese young women on social media

Frontiers in Psychology · 2025-12-18

Social media has transformed how Chinese women present themselves and provided templates for constructing self-identity; female users engage in self-representation by sharing photos, videos, and other content, and they form self-perceptions based on external feedback such as real-time interactions and virtual social engagement. This study employed semi-structured in-depth interviews with 23 Chinese female social media users aged 18-35 (20 of which were included in the final analysis), supplemented by non-participant observation across Little Red Book, Douyin, WeChat, and Weibo to examine platform recommendation logics and visual practices. Application of beautification tools and filters has increased on social media platforms, and the normalization of these technologies further alienates women's aesthetic subjectivity, rendering self-objectification a routine part of everyday practice; this imposes an "imaginary tax," that is, the expenditure of time, money, and effort to conform to dominant beauty ideals, and factors such as occupational background and frequency of social media use play a significant role in reinforcing aesthetic objectification by deepening self-surveillance and comparison among female users. Chinese young women should therefore recognize the disciplinary logic embedded in platform algorithms and visual mechanisms, and reconstruct a healthy model of self-identification based on subjectivity and intrinsic value.

Atomic-scale imaging of frequency-dependent phonon anisotropy

Nature · 2025-09-17 · 5 citations