Materials Science
Predicting co-segregation in alloys with solute-solute interactions
Zuoyong Zhang and Chuang Deng
The co-segregation of
impurities in systems with multiple solute species has been widely recognized as an effective strategy for tailoring material properties. However, reliable predictions of co-segregation behavior remain a significant challenge for
alloy design in these systems. In this work, we develop an extended dual-solute (DS) segregation framework to semi-quantitatively predict co-segregation behavior with solute-solute interactions, including both homoatomic and heteroatomic contributions. A machine-learning workflow is first established to predict the pairwise segregation energy to construct the DS segregation energy spectra that intrinsically include both types of solute-solute interactions. The resulting spectral information is then used to determine the upper and lower bounds of segregation for individual solute species. When applied to magnesium-based ternary systems constructed by alloying Mg with any two of the 11 candidate solute species (Ag, Al, Ca, Co, Cu, Gd, Nd, Ni, Pb, Pd, and Zn), the extended DS segregation framework is successfully validated by hybrid molecular dynamics/Monte Carlo simulations and experimental results available in the literature. Furthermore, we introduce a design strategy to promote co-segregation by incorporating additional solute species that exhibit attractive interactions with existing solutes, thereby enabling enhanced co-segregation even in the presence of strong site competition. These results underscore the critical role of solute-solute interactions in governing co-segregation behavior and provide a predictive pathway for the design and optimization of
alloys.
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Mesoscale and Nanoscale Physics
Disorder induced time-reversal-odd nonlinear spin and orbital Hall effects
Ruda Guo, Yi Liu, Cong Xiao et al. (+1 more)
We develop a theory for the second-order time-reversal-odd ($\mathcal{T}$-odd) angular-momentum current, incorporating both
spin and orbital components. We reveal that besides
spin and orbital Berry
curvature dipoles, $\mathcal{T}$-odd nonlinear angular-momentum current can originate from disorder-induced mechanisms including coordinate shift, side-jump
spin and orbital currents, anomalous scattering amplitude, and skew scattering. A general scaling relation is derived to help distinguish some of these contributions in experiments. Model calculations demonstrate that the orbital component can be comparable to and much larger than the
spin component. Our theory lays the groundwork for $\mathcal{T}$-odd nonlinear
spin and orbital transport.
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All authors Ruda Guo, Yi Liu, Cong Xiao, Zhe Yuan
Soft Condensed Matter
Laddering of a knitted fabric: a topology-induced failure
Antoine Faulconnier, Laura Michel, Mokhtar Adda-Bedia et al. (+2 more)
Laddering is the propagation of a topological defect in an everyday-life material: weft knitted fabrics, following a broken thread or a dropped stitch. What is a minor frustration when damaging a pair of tights is a more serious issue for industrial-scale production, but might inspire new solutions to limit and mitigate damage to architected materials. In this work, laddering is investigated in a pre-stressed model knit through experiments and Discrete Element Rod simulations. The control parameter is the initial tension applied on the fabric. A force threshold due to the stitch's natural
curvature is evidenced. It controls both the propagation onset and arrest, as tension is relaxed by the thread length freed by ladder growth, and enables damage prediction at moderate tension. Furthermore, we uncovered that the laddering velocity is of the order of the velocity of bending waves and exhibits an unexpected linear scaling with the fabric tension, that arises from a complex combination of elastic and friction forces. Finally, we discuss the implications of our results from the perspective of damage control and mitigation.
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All authors Antoine Faulconnier, Laura Michel, Mokhtar Adda-Bedia, Jérôme Crassous, Audrey Steinberger
Other Condensed Matter
Exact analytical edge states in the extended Su-Schrieffer-Heeger model
P. A. Grizzi, A. A. Aligia and P. Roura-Bas
We investigate the
topology of the different phases of the extended Su-Schrieffer-Heeger (eSSH) model, which includes hopping processes between translationally inequivalent atoms beyond nearest neighbors. Exact analytical expressions for the edge states of a semi-infinite eSSH chain are derived, with wave functions that decay exponentially from the boundary with a unit-
cell decay factor z. From the winding number of the bulk
Hamiltonian under periodic boundary conditions, we determine the topological phase diagram and establish the bulk-boundary correspondence: changes in the winding number coincide with bulk gap closings and with the condition |z|=1 for the edge-state solutions. For finite chains, we further obtain analytical, approximate expressions for the low-energy edge states, which are shown to be highly accurate.
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Materials Science · Cross-listed from physics.ins-det
Predictive drift compensation of multi-frame STEM via live scan modification
Matthew Mosse, Jonathan J.P. Peters, Eoin Moynihan et al. (+4 more)
Scanning transmission electron microscopy (STEM) is widely used tool for materials characterisation. However, being a scanned technique, STEM is susceptible to sample, stage or beam drift, manifesting as distortions within images or movement in the field-of-view during multi-frame imaging. Often this is corrected post-acquisition using image registration of multiple frames, but drift reduces the usable area common to all frames. Here we present a method to mitigate sample drift by analysing past frames to predict the sampling-grid points for the immediately future frame. We present this correction across two time-scales and two lengthscales. By offsetting the scan-grid framewise we remove long-range drift, and offsetting pixelwise we minimise intra-image warping. Examples are presented for both atomic-resolution imaging and lower-magnification in-situ
video capture. The framework is general to raster, serpentine, interlaced and other scan patterns, as well as sequential or scan-rotation series STEM.
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All authors Matthew Mosse, Jonathan J.P. Peters, Eoin Moynihan, James A. Gott, Ana M. Sanchez, Michele Conroy, Lewys Jones
Materials Science
A computational alloy design framework for the promotion of amorphous grain boundary complexions
Prince Sharma, Jaime Marian, Jason R. Trelewicz et al. (+1 more)
Amorphous grain boundary complexions have been shown to be radiation tolerant interfaces that can also reduce grain boundary embrittlement, marking them as favorable microstructural features. However, the incorporation of these features into new
alloy systems is often a slow and arduous process based on trial and error. Here, a computational framework for
alloy design is presented which enables the selection of dopants that promote the formation of amorphous grain boundary complexions. This framework is primarily built on density functional theory calculations and is demonstrated for W-rich binary and ternary
alloys, which represent a promising target for fusion energy materials. Our framework first evaluates the grain boundary segregation tendency of dopants and then the energy penalty for amorphization alongside targeted interfacial energy comparison, with the end goal of identifying the best dopants. For a W base, Y and some transition metals such as Co and Ni are found to significantly lower these energetic barriers. Electronic structure analysis, local
lattice distortion, and charge density distributions are calculated and used to provide mechanistic explanations for these dopant selections. Finally, the framework is validated by comparing with experimental literature for W
alloys and a refractory complex concentrated
alloy, showing a strong correlation between our dopant selections and low sintering onset temperatures that have been attributed to activated sintering. As a whole, this work establishes a transferable pipeline for designing
alloys with grain-boundary complexions across diverse
alloy systems.
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All authors Prince Sharma, Jaime Marian, Jason R. Trelewicz, Timothy J. Rupert
Superconductivity
Discovery of parity-violating chiral polar-nematic charge density wave and superconductivity in kagome metals
Xingwei Shi, Geng Li, Zhan Wang et al. (+16 more)
Nonmagnetic kagome metals and
superconductors AV3Sb5 (A = K, Rb, Cs) host unconventional charge density wave (CDW) and superconducting (SC) phases accompanied by multiple electronic
symmetry breaking. Due to the centrosymmetric
crystal structure, inversion
symmetry has generally been assumed to hold. Here, using scanning tunneling microscopy complemented by atomic force microscopy and optical second-harmonic generation, we directly reveal that inversion
symmetry in the kagome plane is spontaneously broken in the CDW state. The mixed-parity CDW state exhibits ferroelectric dipolar and nematic quadrupolar ordered moments. The coexistence and coupling between the dipole and quadrupole favor noncollinear ferro-polar and nematic
alignment that breaks all mirror
symmetries and gives rise to robust electronic chirality in the 3Q CDW. The multipolar coupling to in-plane electric field enables electric field control and manipulation of the
chiral polar-nematic CDW state, including its chirality. Below the SC transition, we observe parity-violating pair density modulations at both the original and the CDW
lattice wavevectors. Our findings of parity-violating electronic
chiral multipolar order provide microscopic insights into the magnetoelectric and nonreciprocal transport, loop current order, pairing density waves, and unconventional superconductivity in kagome metals and related
quantum materials.
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All authors Xingwei Shi, Geng Li, Zhan Wang, Chuqi Zhang, Ke Zhu, Keyu Zeng, Zikun Tang, Li Huang, Zhen Zhao, Jianping Sun, Xiao Liu, Jin-Guang Cheng, Chengmin Shen, Shu Ping Lau, Kian Ping Loh, Haitao Yang, Xiao Lin, Ziqiang Wang, Hong-Jun Gao
Mesoscale and Nanoscale Physics
Memristive Switches in Rigid Conjugated Single-Molecule Junctions
Riccardo Conte, Lucienne van der Geest, Minu Sheeja et al. (+3 more)
Voltage-driven memristive switching has been reported in molecular junctions, yet its microscopic origin often remains elusive. Here, we study three rigid OPE-like derivatives that lack an obvious internal switching pathway using mechanically controlled break junctions (MCBJs) and observe non-volatile, bistable hysteretic IV characteristics at cryogenic temperature. We introduce a quantitative analysis workflow that classifies memristive IVs, clusters the two conductance states, and extracts switching features and stability metrics from repeated measurements at fixed displacement. While all molecules exhibit memristive behavior, stability and hysteresis reproducibility depend strongly on anchoring and connectivity: the linear biphenyl backbone with thiolate (SAc) anchoring shows the most reproducible, predominantly field-driven hysteresis, whereas the meta-phenyl variant with thioether (SMe) anchoring is dominated by
stochastic, current-driven events. The resulting conductance statistics point to an extrinsic, mechanically mediated origin involving contact rearrangements, multi-molecule transport, blinking (open-closed) contacts, injection-point shifts, and $\pi$-$\pi$-stacking dimerization.
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All authors Riccardo Conte, Lucienne van der Geest, Minu Sheeja, Przemyslaw Gawel, Cina Foroutan-Nejad, Herre S. J. van der Zant
Materials Science
Bulk and surface electronic structure of MoAlB(010)
Gianmarco Gatti, Amalie H. Svaneborg, Wu Bing et al. (+11 more)
The bulk and surface electronic structure of MoAlB(010) is studied by a combination of angle-resolved photoemission spectroscopy and density functional calculations. The observed bulk
Fermi-level crossings agree with the previously reported bulk
Fermi surface of the material. Additionally, we find several surface states in the wide projected bulk band gaps around the
Fermi energy. The surface states differ in their stability under residual-gas exposure in the
vacuum system and in the magnitude of their Rashba-type
spin-orbit splitting. We explain this in terms of their elemental and orbital character. A surface state arising from Al dangling bonds is sensitive to surface contamination, whereas a mainly Mo-derived surface state exhibits the stronger
spin-orbit splitting. The surface states show
symmetry-enforced crossings near the $\bar{\mathrm{S}}$ point of the surface Brillouin zone. These are protected by the mirror-
symmetry elements of the p2mm wallpaper group.
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All authors Gianmarco Gatti, Amalie H. Svaneborg, Wu Bing, Gesa-R. Siemann, Anders S. Mortensen, Naina Kushwaha, Jennifer Rigden, Jakob K. Svaneborg, Matthew D. Watson, Timur K. Kim, Charlotte E. Sanders, Kristian S. Thygesen, Zdenek Sofer, Philip Hofmann
Disordered Systems and Neural Networks · Cross-listed from q-bio.NC
Response time of lateral predictive coding and benefits of modular structures
Guanghui Cai, Zhen-Ye Huang, Weikang Wang et al. (+1 more)
Lateral predictive coding (LPC) is a simple theoretical framework to appreciate feature detection in biological neural
circuits. Recent theoretical work [Huang et al., Phys.Rev.E 112, 034304 (2025)] has successfully constructed optimal LPC networks capable of extracting non-Gaussian hidden input features by imposing the tradeoff between energetic cost and information robustness, but the resulting dynamical systems of recurrent interactions can be very slow in responding to external inputs. We investigate response-time reduction in the present paper. We find that the characteristic response time of the LPC system can be minimized to closely approaching the lower-bound value without compromising the mean predictive error (energetic cost) and the information robustness of signal transmission. We further demonstrate that optimal LPC networks taking a modular structural organization with extensively reduced number of lateral interactions are equally excellent as all-to-all completely connected networks, in terms of feature detection performance, response time, energetic cost and information robustness.
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All authors Guanghui Cai, Zhen-Ye Huang, Weikang Wang, Hai-Jun Zhou
Materials Science
Accurate and Efficient Interatomic Potentials for Dislocations in InP
Thomas Rocke, Thomas Hudson, Richard Beanland et al. (+1 more)
We present Atomic Cluster Expansion (ACE) and MACE models trained on a new
dataset of Density Functional Theory (DFT) calculations, constructed for the task of studying the mobility of dislocations in Indium Phosphide (InP). The models are validated in a suite of tests against RSCAN DFT, and compared with previously published potentials from literature. Our new models act as much better surrogates for DFT than the literature models: errors on partial dislocation formation energies are at most 4% for both ACE and MACE, compared with 18% for the MACE-MPA foundation model and 42-50% for earlier bespoke potentials. The bespoke MACE model achieves this accuracy while being around five times faster to evaluate than the MP0 and MPA foundation models.
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All authors Thomas Rocke, Thomas Hudson, Richard Beanland, James Kermode
Mesoscale and Nanoscale Physics
Modeling of flopping-mode spin qubits: beyond the two-site model
Ashutosh Kinikar, Vukan Levajac, Kristof Moors et al. (+3 more)
We present a flexible modeling framework for flopping-mode
spin qubits that captures the spatial structure of the double-well confinement and
magnetic-field-gradient profile going beyond conventional low-energy descriptions. By using this approach, we simulate electric dipole
spin resonance-based single-
qubit control and evaluate the frequency and spectral purity of the Rabi oscillations across different parameter regimes. Our analysis reveals a fundamental tradeoff between fast electrical driving and clean single-mode Rabi oscillations, and demonstrates that the standard two-site low-energy approximation can overestimate the Rabi frequency by up to $\sim$ 20% in certain parameter regimes. We also investigate two-
qubit control by considering two capacitively coupled flopping-mode
qubits and derive the corresponding exchange interaction with an appropriately restricted configuration interaction treatment. Our approach reveals the interplay between the spatial profile of the double-well confinement,
magnetic field gradient, and Coulomb interaction, which together govern the effective exchange coupling strength. Our spatially resolved modelling framework enables efficient exploration of double-well confinement parameters and
magnetic field gradient profiles, enabling a transparent mapping from spatial device properties to flopping-mode
qubit parameters and quality metrics.
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All authors Ashutosh Kinikar, Vukan Levajac, Kristof Moors, George Simion, Monica Benito, Bart Soree
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Valley-Aware Optimal Control of Spin Shuttling Using Cryogenic Integrated Electronics
Pau Dietz Romero, Nermine Chaabani, Lammert Duipmans et al. (+4 more)
Electron shuttling is emerging as a key mechanism for enabling long-range coupling in scalable
spin-
qubit architectures. Bringing shuttling waveform generation into the cryostat can improve scalability, but imposes strict area and power constraints on the control electronics. Concurrently, shuttling in Si/SiGe is further limited by a spatially varying valley splitting that induces
spin–valley mixing and degrades coherence. Here, we make three contributions that address these limitations jointly: (i) an end-to-end co-simulation framework that combines disorder-informed valley maps with transistor-level cryogenic
circuit simulations including electronic noise; (ii) a fully integrated cryogenic shuttling-signal generator tailored to velocity modulation, enabling period-wise waveform shaping through discrete
circuit settings stored in on-chip
memory; and (iii) a noise-aware optimization procedure that tunes only these implementable
circuit controls, using one of four discrete resistor settings per period, to generate high-fidelity shuttling sequences. Across simulated valley and noise realizations in our co-simulation framework, the optimized velocity-modulation waveforms improve transport performance, achieving an average shuttling fidelity of $99.99 \pm 0.007\%$ at $v_{\mathrm{avg}} = 20~\mathrm{m\,s^{-1}}$ over a distance of $10~\mu\mathrm{m}$, while maintaining active analog power consumption in the tens of $\mu\mathrm{W}$ during shuttling. This validates on-chip storage and replay of optimized control settings as a practical strategy to mitigate valley disorder in scalable shuttling architectures.
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All authors Pau Dietz Romero, Nermine Chaabani, Lammert Duipmans, Alessandro David, Felix Motzoi, Stefan van Waasen, Lotte Geck
Mesoscale and Nanoscale Physics
Spin-wave hybridization in bismuth iron garnet Mie spheres induced by the inverse Faraday effect
Fedor Shuklin, Khristina Albitskaya, Alexander Chernov et al. (+1 more)
We show that the inverse Faraday effect can be used to engineer dipole–exchange
spin-wave spectra in ferrimagnetic bismuth iron garnet (BIG) Mie spheres. Internal optical Mie resonances generate spatially structured effective
magnetic fields whose
symmetry is inherited from the optical near field and which act as controllable perturbations of the
magnon Hamiltonian. For circularly polarized light incident collinearly with the
equilibrium magnetization, the optical perturbation preserves axial
symmetry while breaking mirror parity, thereby enabling hybridization of
magnon modes with opposite parity within the same $\widehat{J}_z$ sector. Using coupled-mode theory, we derive the corresponding avoided-crossing spectrum and analytical expressions for the induced level splittings, which scale linearly with pump intensity. Numerical calculations for BIG spheres confirm the predicted hybridization and show that the splitting is maximized near optical Mie resonances, where field enhancement and magneto-optical response are strongest. We further discuss the roles of damping, linewidth, and heating, and show that the predicted MHz–hundreds-of-MHz splittings should be observable under realistic conditions. These results identify BIG Mie resonators as a promising platform for
symmetry-selective optical control of
spin-wave spectra.
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All authors Fedor Shuklin, Khristina Albitskaya, Alexander Chernov, Mihail Petrov
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Control Over Fano Parameter in Grating and One-Dimensional Photonic Crystal Cavity
Pratip Ghosh and Akshay K. Naik
Fano resonances are sharp asymmetrical spectral peaks which are now ubiquitous in nanophotonics. The high sensitivity of these resonances to system parameter has been exploited to improve light matter interaction and in applications such as sensing, filters and on-chip processing. The ability to dynamically change the Fano slope and spectral phase would enable optimization of the device parameters post fabrication for various applications. Here we demonstrate such a control over the Fano resonance in a one-dimensional photonics
crystal cavity integrated on a silicon waveguide -grating platform. In our device, Fano resonance arises due to interference between cavity mode and an oscillatory background due to grating coupler. The dynamics tuning of Fano asymmetric parameter is achieved using thermos-optic effect in silicon. We experimentally tune the Fano parameter from ~-3.2 to +1.7 achieving a highest extinction ratio of 21.6 dB and spectral slope of 108dB/nm. All the above is achieved in an ultra-compact design with simple fabrication and with multiple cavities or feedback elements. The steep slope offers distinct advantage over conventional cavity for sensing and modulation applications and the tunability enables dynamic control over gain, dynamic range, bandwidth and noise coupling.
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Materials Science
Including nanoparticle shape into macrospin models
Iago López-Vázquez, Òscar Iglesias and David Serantes
We investigate the feasibility of the macrospin approximation to account for the actual shape of soft
magnetic nanoparticles (MNPs) with realistic geometries. Specifically focusing on magnetite, we use the superellipsoidal parametrisation to account for a variety of shapes, with a continuous interpolation from spherical to cubic morphologies, as well as different elongations. Our procedure consists of the direct comparison between angular-dependent hysteresis loops obtained by full micromagnetic simulations, with those produced by an extended Stoner-Wohlfarth (SW) model that incorporates both the intrinsic cubic magnetocrystalline anisotropy, and an effective uniaxial contribution arising from the particle elongation. The limits of validity of the macrospin description are approximately 10-60 nm for axial ratios r>1.5, and 20-60 nm for 1.0<r<1.5. These results establish a direct connection between nanoparticle morphology and effective macrospin parameters, demonstrating the suitability of the generalized SW model for describing the
magnetic response of realistically shaped MNPs.
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Soft Condensed Matter
Programming strain-stiffening in soft composites via structural memory near jamming
Yiqiu Zhao, Deng Pan, Yiming Pang et al. (+6 more)
Soft composite solids, comprising discrete inclusions embedded within a compliant
matrix, are emerging candidates for engineering synthetic tissues and soft robotic materials. Current strategies for controlling their nonlinear mechanics, such as strain-stiffening, have primarily relied on the nonlinear elasticity of
polymer matrices. Although direct contacts between inclusions may enhance stiffening responses at high densities, the role of the non-
equilibrium and history-dependent nature of disordered contact networks in composite mechanics remains unexplored. In this work, by applying a mechanical training protocol near a shear-jamming phase boundary, we demonstrate that the structural
memory encoded in contact networks drives a crossover from granular-like to biopolymer-like strain stiffening. Simulations of a coarse-grained composite model reveal that this biopolymer-like mechanical response emerges from enhanced non-affine reconfigurations of nearly-jammed contact networks. Without relying on
matrix nonlinearity, we establish a design strategy that leverages non-
equilibrium memory effects intrinsic to granular systems to achieve highly programmable strain-stiffening in soft composites.
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All authors Yiqiu Zhao, Deng Pan, Yiming Pang, Jonathan Barés, Chang Xu, Che Liu, Haitao Hu, Yuliang Jin, Qin Xu
Materials Science
Phonon driven non-equilibrium triggers for thermal runaway in battery electrodes
Harry Mclean, Francis Huw Davies, Ned Thaddeus Taylor et al. (+2 more)
Thermal runaway in lithium-ion batteries is governed by the poorly-understood initiation phase, where localised heating introduces instability. Here we identify the three key components that trigger thermal runaway, decreases in local conductivity, heat capacity changes, and intercalation heating, which significantly increase temperature gradients that accelerate battery degradation. Using a multiscale framework that links atomistic
phonon calculations with grain-resolved thermal modelling, we identify large thermal gradients across grain boundaries arising from external heating events and intercalation-dependent thermal properties of Li$_x$ZrS$_2$. The observed changes in thermal conductivity are due to charge redistribution and bond-strength modulation of the host, in contrast to the existing theory of lithium rattler mechanics. Internal heating events driven by intercalation gives rise to local thermal gradients, finite-speed thermal wave interference, and internal thermal fluctuations that generate mechanical strain and sub-grain thermal breakdown. These results show that the trigger for thermal runaway is controlled by internal grain architecture and composition, as well as the external environment. Our findings establish materials and electrode design rules for suppressing hotspot formation and improving battery safety during fast charging.
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All authors Harry Mclean, Francis Huw Davies, Ned Thaddeus Taylor, David W. Horsell, Steven P. Hepplestone
Statistical Mechanics
Quantum many-body scars leading to time-translation symmetry breaking in kicked interacting spin models
Ángel L. Corps, Armando Relaño and Angelo Russomanno
We study an Ising model with long-range interactions undergoing a time-periodic kicking. For different initial states we observe persistent period doubling. When there is period doubling we find that the initial state has relevant overlap with Floquet states showing time-translation
symmetry breaking, organized in doublets displaying $\pi$-spectral pairing (as highlighted by the $\pi$-spectral gap) and long-range order (as shown by the
eigenvalues of the magnetization in the doublet). We observe period doubling for initial states with domain walls and tilted
spins, and for the latter ones a finite-size scaling of the relevant $\pi$-shifted gap and magnetization
eigenvalues suggests period-doubling oscillations persisting for larger system sizes and lasting a time exponential in the system size. We find that just a minority of Floquet states displays time-translation
symmetry breaking while the rest is thermal, a weak-ergodicity breaking situation typical of systems with
quantum scars. Although the time-translation
symmetry breaking eigenstates are the minority, their number is exponential in the system size and this motivates the period doubling observed for many different initial states.
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Quantum Gases
Vortex dipoles in expanding shell-shaped Bose-Einstein condensates
A. Tononi
Releasing shell-shaped Bose-Einstein condensates from the external confinement produces a spherically symmetric density distribution characterized by concentric ripples surrounding a central peak. Here we investigate how a
vortex-antivortex dipole affects this dynamics, finding that increasing dipole separation progressively breaks the spherical
symmetry. Correspondingly, the interplay of
vortex physics and
curvature produces a nonmonotonic behavior of the cloud aspect ratio with the
vortex distance, and decreases the maximal central density achieved during the expansion. These features can be used for detecting
vortex dipoles prepared in shell-shaped superfluids, as well as a basis for analyzing their signatures in other thin superfluids with more general curved geometries.
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Soft Condensed Matter
Controlling microgel morphology and swelling behavior by copolymerization
Domenico Truzzolillo, Thomas Hellweg and Julian Oberdisse
The thermosensitive behavior of microgel particles suspended in solvents, i.e. their temperature-dependent swelling properties, has triggered ongoing interest in industry and academia over the past forty years. The most-studied
polymer is poly(N-isopropylacrylamide) - PNIPAM -, where the volume phase transition temperature is well known to depend on the detailed molecular architecture of the monomers. In this article, we focus on publications mostly of the past five years in chemical synthesis, aiming at shifting or controlling the volume phase transition temperature (VPTT) of such
polymers by copolymerization of a main monomer - often from the PNIPAM family - with either monomers of different hydrophobicity, or with ones bearing ionizable groups. In some cases, hydrophobicity may be modulated by light as external switching parameter, whereas ionic strength or pH may act on the thermosensitivity of the microgels containing charged groups. Due to either differences in reactivity, or specific synthesis routes, particular microgel morphologies, such as molecular gradient, core-shell, interpenetrated, or patchy (multi-lobular) structures may be generated. They may give rise to spatial modulations of thermosensitivity within particles and are highlighted in this review. Our short overview shows that multiple external control of VPTT and morphology is commonly achieved nowadays.
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Materials Science
Second-order topology in two-dimensional azulenoid kekulene carbon lattices
Xiaorong Zou, Hyeon Suk Shin, Chang-Jong Kang et al. (+5 more)
The discovery of higher-order topological
insulator (HOTI) has established a new paradigm for understanding
symmetry-constrained boundary electronic states. Here, based on first-principles calculations, we demonstrate the emergence of HOTI phase in organic
lattices of two-dimensional azulenoid-kekulene-type carbon allotropes, namely AKC-[3,3] and AKC-[6,0]. Enabled by the $C_6$ rotational
symmetry, the nontrivial bulk
topology is confirmed through the topological invariant and fractionally quantized corner charge, giving $\{[M^{(I)}_{2}],[K^{(3)}_{2}]\}$ = $\{0,2\}$ and $Q_{\mathrm{corner}} = e/3$, respectively, accompanied by the emergence of exotic corner states in nanoflakes. Notably, the structural modifications are explored, revealing that in the derived structure PAK-[6,0], whose corner-localized states are preserved, highlighting the robustness of the higher-order topological phase. These findings highlight azulenoid-kekulene-based carbon allotropes as a promising platform to explore the interplay between structural design, crystalline
symmetry, and higher-order topological boundary responses in two dimensional carbon systems.
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All authors Xiaorong Zou, Hyeon Suk Shin, Chang-Jong Kang, Baibiao Huang, Yanmei Zang, Ying Dai, Chengwang Niu, Chang Woo Myung
Mesoscale and Nanoscale Physics
Quantum Optical Signatures of Band Topology in Solid-State High Harmonics
Denis Ilin, Alexander S. Solntsev and Ivan Iorsh
We develop a general theory of high-harmonic generation (HHG) in solid-state systems, based on a weak-correlation expansion of photonic and matter degrees of freedom. Unlike standard HHG theories, which treat light-matter dynamics through the Schrodinger equation, our approach employs density-
matrix evolution, naturally capturing the mixed-state character of both the field and the matter - a critical aspect for describing complex solid-state band structures. We show explicitly that the properties of the emitted fields are governed by the
quantum statistics and
quantum geometry of the underlying solid. Taking the Su-Schrieffer-Heeger (SSH) model in a one-sided optical cavity as a paradigmatic example and considering the dual regime, we demonstrate that in the topological phase a system exhibits a stronger HHG response and stronger
quantum-light signatures than in the trivial phase. Furthermore, we show that cavity-matter interaction gives rise to squeezed high-harmonic
quantum light, whose properties are directly imprinted by the current-current fluctuations in the material system. Crucially, the observed squeezing does not rely on a separate quartic Kerr mechanism. In the mesoscopic regime, the genuine
quantum Kerr term is higher order in light-matter coupling strength and negligible, while the relevant non-classical effect is governed by current-current fluctuations encoded in the complex susceptibility of the material. This work establishes a direct link between band
topology and
photon statistics, opening new avenues for
topology-sensitive
quantum light generation and
photon statistics based spectroscopy of solid-state systems.
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Statistical Mechanics
Spectral Fluctuation-Dissipation-Response Inequalities
Jie Gu
We derive spectral fluctuation–dissipation–response inequalities for finite-state Markov jump processes. By comparing the causal susceptibility to its passive
equilibrium reference, we establish frequency-resolved and frequency-integrated inequalities that bound their mismatch in terms of the steady-state
entropy production rate, probe variance, short-time perturbation
diffusion, and reversible relaxation timescales. Our bounds exactly recover the standard fluctuation–dissipation
theorem at
equilibrium and apply directly to measurable causal susceptibilities, providing experimentally testable thermodynamic limits on FDT breakdown in driven steady states.
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Mesoscale and Nanoscale Physics
Symplectic connection third-order Hall effect in a room-temperature ferromagnet
Yu Cao, Xukun Feng, Yiming Guo et al. (+18 more)
Third-order nonlinear
Hall effects (THE) have recently attracted considerable experimental interest as powerful probes for
quantum geometric properties in emergent
quantum materials, encompassing quadrupole moments of
quantum metric and Berry
curvature. Here, we report a fundamentally new THE in room-temperature van der Waals ferromagnet Fe3GaTe2 from second-order Berry connection polarizability, which manifests a higher-order characterization of band geometry called
symplectic connection. Our observations show that the third-order transverse response in Fe3GaTe2 is odd to magnetization, vanishes above the Curie temperature and remains independent of driving current directions. Scaling law analysis combined with first-principles calculations establishes this response as the
symplectic-connection-induced THE. This discovery opens the door to probing high-order
quantum geometric properties beyond Berry
curvature and
quantum metric through nonlinear transport, unveiling the potential of exploring nonlinear
Hall phenomena in broad classes of magnets without breaking inversion
symmetry. Moreover, the room-temperature manipulation of THE holds promises for device applications based on harnessing the
quantum-
geometric connection structure.
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All authors Yu Cao, Xukun Feng, Yiming Guo, Huiying Liu, Qia Shen, Hongliang Chen, Wanxi Gong, Yu Yang, Dandan Guan, Yaoyi Li, Shiyong Wang, Hao Zheng, Canhua Liu, Xiaoxue Liu, Yumeng Yang, Xuepeng Qiu, Ruidan Zhong, Jinfeng Jia, Shengyuan A. Yang, Cong Xiao, Liang Liu
Materials Science
Fluctuation-driven multi-step charge density wave melting in monolayer TiSe$_2$
Luka Benić, Dino Novko and Ivor Lončarić
The exact microscopic origin,
symmetry, and thermal melting mechanism of the charge density wave (CDW) phase in TiSe$_2$ remain intensely debated, particularly regarding
chiral structural order and multi-step phase transitions. Using large-scale molecular dynamics driven by an accurate machine-learning interatomic potential, we resolve the finite-temperature structural dynamics of the monolayer TiSe$_2$. We demonstrate that CDW melting deviates from conventional mean-field second-order behavior, undergoing a two-step process characterized by an extended fluctuation region ($200-250$ K) with proliferating domain walls, phase decoherence, component-selective melting, and an overdamped soft optical
phonon. Furthermore, anisotropic long-wavelength thermal fluctuations spontaneously stabilize an asymmetric $3Q$ CDW order with $P1$
symmetry. These findings provide a unified microscopic framework for fluctuation-driven transitions in 2D
quantum materials, demonstrating that the complex CDW physics of TiSe$_2$ is captured entirely via non-perturbative electron-
phonon and
phonon-
phonon interactions.
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Strongly Correlated Electrons
Disorder-driven coexistence of distinct dynamical states in frustrated Sr$_3$CuNb$_2$O$_9$: a microscopic $\mu$SR and $^{93}$Nb NMR study
M. Biswas, K. Bhattacharya, K. M. Ranjith et al. (+8 more)
Despite recent progress in identifying the exotic random singlet (RS) state in disordered frustrated magnets as a distinct correlated phase, three-dimensional (3D) realizations remain scarce. Sr$_3$CuNb$_2$O$_9$ was proposed to be one of such 3D frustrated systems with
magnetic site disorder hosting an RS ground state. Here, we report a detailed microscopic investigation of Sr$_3$CuNb$_2$O$_9$ employing
muon spin relaxation ($\mu$SR) and $^{93}$Nb
nuclear magnetic resonance (NMR) techniques. The $\mu$SR zero-field relaxation rate reveals a power-law divergence of the relaxation rate as a function of temperature. Also, a power-law divergence is present in the relaxation rate as a function of applied longitudinal field, consistent with the formation of an RS phase. The $^{93}$Nb NMR spectra unambiguously resolve two components with distinct local
magnetic environments, whose nature is further elucidated through
spin-
lattice relaxation measurements analyzed via an inverse Laplace transform (ILT) of the
nuclear magnetization recovery. The relaxation-rate distribution obtained from ILT reveals two well-separated channels: a fast component, $(1/T_1)_{\mathrm{fast}}$, and a slow component, $(1/T_1)_{\mathrm{slow}}$. Both components follow distinct power-law temperature dependences ($T^{\alpha}$), with $\alpha = 0.6$ and $1.1$ for the fast and slow channels, respectively. The combined spectral and relaxation data demonstrate that the fast channel qualitatively represents an RS-like state, whereas the slow channel exhibits
quantum spin liquid (QSL) like behavior, thereby establishing the microscopic coexistence of RS and QSL-like phases in Sr$_3$CuNb$_2$O$_9$.
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All authors M. Biswas, K. Bhattacharya, K. M. Ranjith, S. M. Hossain, S. S. Islam, M. Naskar, R. Sarkar, B. Büchner, T. Shiroka, H.-J. Grafe, M. Majumder
Superconductivity
Perfect spin nonreciprocity in gated superconducting altermagnetic heterostructures
Pei-Hao Fu, Jun-Feng Liu, Luca Chirolli et al. (+1 more)
We consider a superconducting altermagnet
heterostructure and demonstrate that the interplay between altermagnetism and a selective filter of transverse momentum channels enables perfect nonreciprocal
spin-polarized currents. We demonstrate that this nonreciprocity manifests in both local and nonlocal
spin currents, signalling the emergence of directionally selective local and nonlocal
spin behaviors. We show that the selective filter of transverse momentum channels is realized by gating a finite normal region between the superconducting altermagnet and the metallic reservoir, which then directionally selects transport channels that match the momentum-dependent
spin-split superconducting altermagnetic states, allowing for nonreciprocal
spin-polarized currents. We discover that the local and nonlocal
spin nonreciprocity features a highly tunable polarity and nearly perfect quality factors, respectively, which is achieved by means of gate voltages and by varying the length of the finite region. Moreover, we find that local and nonlocal charge currents also develop a nonreciprocal behavior, whose quality factors can also reach perfect values. In all cases, the
spin and charge currents are sensitive to variations of the altermagnetic field, a functional dependence that can be exploited to identify the type of altermagnetism. Our findings put forward an electrically controllable route towards nonreciprocal superconducting spintronic devices based on altermagnets.
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All authors Pei-Hao Fu, Jun-Feng Liu, Luca Chirolli, Jorge Cayao
Materials Science
Multilayer Laue Lenses for Enhanced Spatial Resolution in Dark-Field X-ray Microscopy
Steffen Staeck, Can Yildirim, Raquel Rodriguez-Lamas et al. (+5 more)
We introduce the use of a crossed pair of Multilayer Laue Lenses (MLLs) as an objective in Dark-Field X-ray Microscopy (DFXM). In a demonstration experiment at the ID03 beamline at ESRF, two flat Mo-Si MLLs were used, with a physical aperture of 50 x 50 $\mathrm{\mu m^2}$ and a focal length of 14.25 mm at 19 keV. Applying a 10 % criterion to the Modulation Transfer Functions (MTFs) acquired, a spatial resolution of 56 nm is obtained in bright-field mode – more than three times better than with a compound refractive lens (CRL) objective. The dark-field resolution is similar. With an efficiency of 26.7 % the MLL objective expands the science domain of DFXM significantly, both for bulk and near-surface studies. Similar to the CRL case, the reciprocal space resolution is dominated by the numerical aperture (NA) of the objective, with the NA being three times larger in the MLL case. This enables faster orientation mapping and implies improved options for the use of tomographic reconstruction
algorithms. Although the MLL objective pupil varies with energy and position, secondary peaks are suppressed, simplifying both interpretation and forward simulations. We present an example DFXM application using the MLL as an objective, imaging a through-silicon via Kelvin device.
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All authors Steffen Staeck, Can Yildirim, Raquel Rodriguez-Lamas, Thomas Dufrane, Carsten Detlefs, Nis Gellert, Antonella Gayoso Padula, Henning Friis Poulsen
Materials Science
LLM-guided phase diagram construction through high-throughput experimentation
Ryo Tamura, Haruhiko Morito, Yuna Oikawa et al. (+7 more)
Constructing phase diagrams for multicomponent
alloys requires extensive experimental measurements and is a time-consuming task. Here we investigate whether large
language models (LLMs) can guide experimental planning for phase diagram construction. In our framework, a general-purpose LLM serves as the experimental planner, suggesting compositions for measurement at each cycle in a closed loop with high-throughput synthesis and X-ray diffraction phase identification. Using this framework, we experimentally constructed the ternary phase diagram of the Co-Al-Ge system at 900 degree C through iterative synthesis and characterization. We compared two strategies that differ in how the initial compositions are selected: one uses predictions from a domain-specific LLM trained on phase diagram data (aLLoyM), while the other relies solely on the general-purpose LLM. The two strategies exhibited complementary strengths. aLLoyM directed the initial measurements toward compositionally complex regions in the interior of the ternary diagram, enabling the earliest discovery of all three novel phases that form only in the ternary system. In contrast, the general-purpose LLM adopted a textbook-like approach which efficiently identified a larger number of phases in fewer cycles. In addition, a simulated
benchmark comparing the LLM against conventional machine learning confirmed that the LLM achieves more efficient exploration. The results demonstrate that LLMs have high potential as experimental planners for phase diagram construction.
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All authors Ryo Tamura, Haruhiko Morito, Yuna Oikawa, Guillaume Deffrennes, Shoichi Matsuda, Naruki Yoshikawa, Tomoaki Takayama, Taichi Abe, Koji Tsuda, Kei Terayama