Mesoscale and Nanoscale Physics
Enhanced Terahertz Photoresponse via Acoustic Plasmon Cavity Resonances in Scalable Graphene
Domenico De Fazio, Sebastián Castilla, Karuppasamy P. Soundarapandian et al. (+11 more)
Precise control and nanoscale confinement of terahertz (THz) fields are essential requirements for emerging applications in photonics,
quantum technologies, wireless communications, and sensing. Here, we demonstrate a polaritonic cavity enhanced THz photoresponse in an
antenna coupled device based on chemical vapor deposited (CVD) monolayer
graphene. The dipole
antenna lobes simultaneously serve as two gate electrodes, concentrate the impinging THz field, and efficiently launch acoustic
graphene plasmons (AGPs), which drive a strong photo-thermoelectric (PTE) signal. Between 6 and 90 K, the photovoltage exhibits pronounced peaks, modulating the PTE response by up to 40%, that we attribute to AGPs forming a Fabry Pérot THz cavity in the full or half
graphene channel. Combined full wave and transport thermal simulations accurately reproduce the gate controlled plasmon wavelength, spatial absorption profile, and the resulting nonuniform electron heating responsible for the PTE response. The lateral and vertical maximum confinement factors of the AGP wavelength relative to the incident wavelength are 165 and 4000, respectively, for frequencies from 1.83 to 2.52 THz. These results demonstrate that wafer scalable CVD
graphene, without hBN encapsulation, can host coherent AGP resonances and exhibit an efficient polaritonic enhanced photoresponse under appropriate gating,
antenna coupling, and AGP cavity design, opening a route to scalable, polarization and frequency selective,
liquid nitrogen cooled, and low power consumption THz detection platforms based on plasmon thermoelectric transduction.
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All authors Domenico De Fazio, Sebastián Castilla, Karuppasamy P. Soundarapandian, Tetiana Slipchenko, Ioannis Vangelidis, Simone Marconi, Riccardo Bertini, Vlad Petrica, Yang Hao, Alessandro Principi, Elefterios Lidorikis, Roshan K. Kumar, Luis Martín-Moreno, Frank H. L. Koppens
Mesoscale and Nanoscale Physics
The 2026 Skyrmionics Roadmap
Sabri Koraltan, Claas Abert, Manfred Albrecht et al. (+64 more)
Magnetic skyrmions and related topological
spin textures have emerged as a central topic in condensed-matter physics, combining fundamental significance with potential for transformative applications in spintronics, magnonics, and beyond. Over the past decade, advances in material platforms, imaging techniques, theoretical modeling, and device concepts have established skyrmionics as a rapidly expanding field. At the same time, challenges remain in stabilizing, controlling, and integrating such textures into functional architectures, while novel phenomena such as antiskyrmions, higher-order skyrmions, hopfions, and
antiferromagnetic textures arise. The 2026 Skyrmionics Roadmap represents a collective effort of many authors, providing a comprehensive perspective on the current state-of-the-art and the outlook for the coming years. In 33 focused sections, each co-authored by two researchers, we chart progress in theory and modeling, material systems, skyrmion dynamics, and skyrmion technologies. By offering a consolidated
vision, this Roadmap aims to guide both fundamental research and application-driven efforts, accelerating the transition of skyrmionics from conceptual breakthroughs toward practical technologies.
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All authors Sabri Koraltan, Claas Abert, Manfred Albrecht, Maria Azhar, Christian Back, Hélène Béa, Max T. Birch, Stefan Blügel, Olivier Boulle, Felix Büttner, Ping Che, Vincent Cros, Emily Darwin, Louise Desplat, Claire Donnelly, Haifeng Du, Karin Everschor-Sitte, Amalio Fernández-Pacheco, Simone Finizio, Giovanni Finocchio, Markus Garst, Raphael Gruber, Dirk Grundler, Satoru Hayami, Thorsten Hesjedal, Axel Hoffmann, Aleš Hrabec, Hans Josef Hug, Hariom Jani, Jagannath Jena, Wanjun Jiang, Javier Junquera, Kosuke Karube, Lisa-Marie Kern, Joo-Von Kim, Mathias Kläui, Hidekazu Kurebayashi, Kai Litzius, Yizhou Liu, Martin Lonsky, Christopher H. Marrows, Jan Masell, Stefan Mathias, Yuriy Mokrousov, Stuart S. P. Parkin, Bastian Pfau, Paolo G. Radaelli, Florin Radu, Ramamoorthy Ramesh, Nicolas Reyren, Stanislas Rohart, Shinichiro Seki, Ivan I. Smalyukh, Sopheak Sorn, Daniel Steil, Dieter Suess, Mykola Tasinkevych, Yoshinori Tokura, Riccardo Tomasello, Victor Ukleev, Hyunsoo Yang, Fehmi Sami Yasin, Xiuzhen Yu, Chenhui Zhang, Shilei Zhang, Le Zhao, Sebastian Wintz
Materials Science
Synergistic effects of ferromagnetic elements and LAGP solid electrolyte in suppressing and trapping polysulfide shuttle transfers in lithium-sulfur batteries
Giovanni Ceccio, Jiri. Vacík, Mykhailo Drozdenko et al. (+4 more)
The large - scale commercialization of promising lithium - sulfur (Li - S) batteries remains limited by the polysulfide shuttle effect, which causes rapid capacity fading and poor cycle life. In this study, we present a scalable strategy to mitigate this challenge by modifying polyethylene (PE) separators with
ferromagnetic and solid - state ionic coatings. Thin films of nickel (Ni), cobalt (Co), and the Li - ion - conducting ceramic Li1.5Al0.5Ge1.5(PO4)3 (LAGP) were deposited via ion beam sputtering, while Ni ion implantation was also employed to modify the PE substrate. The electrochemical performance of pristine and modified separators was evaluated using electrochemical impedance spectroscopy (EIS) and staircase voltammetry (SV) in
liquid electrolyte within H -
cell configurations. Surface morphology and elemental composition were characterized by scanning electron microscopy (SEM) and Rutherford backscattering spectroscopy (RBS). The results show that LAGP-based coatings significantly enhance separator stability and effectively suppress polysulfide
diffusion, leading to lower redox peak intensities and improved cycling performance. In contrast, Ni coatings exhibited poor long - term stability, likely due to parasitic reactions or delamination during its life time. The combined LAGP/Co architecture provided the most effective suppression of the polysulfide shuttle, attributed to synergistic ionic and catalytic effects that promote interfacial stability and selective ion transport. Ni implantation into PE showed only a negligible effect. This study highlights the potential of integrating solid ionic conductors with
ferromagnetic layers to design multifunctional separators for high-performance Li - S batteries.
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All authors Giovanni Ceccio, Jiri. Vacík, Mykhailo Drozdenko, Romana Mikšová, Josef Novak, Eva Štěpanovská, Mayur Khan
Statistical Mechanics
Active Cahn-Hilliard theory for nonequilibrium phase separation: quantitative macroscopic predictions and a microscopic derivation
Sumeja Bureković, Filippo De Luca, Michael E. Cates et al. (+1 more)
Phase-separating active systems can display phenomenology that is impossible in
equilibrium. The binodal densities are not solely determined by a bulk (effective) free energy, but also affected by gradient terms, while capillary waves and Ostwald processes are determined by three distinct interfacial tensions. These and related phenomena were so far explained at continuum level using a top-down minimal theory (Active Model B+). This theory, by Taylor-expanding in the scalar order parameter (or density), effectively assumes that phase separation is weak, which is not true across most of the phase diagram. Here, we develop a quantitative account of active phase separation, by introducing an active counterpart of Cahn-Hilliard theory, constructing the density current from all possible terms with up to four spatial derivatives without Taylor-expanding in the density. From this O(grad^4) theory, we show how to compute binodals and interfacial tensions for arbitrary choices of the five density-dependent 'coefficient functions' that specify the theory (replacing the four constant coefficients of Active Model B+). We further consider a particle model composed of thermal quorum-sensing active particles (tQSAPs) yielding a fully specified example of the O(grad^4) theory upon coarse-graining. We find that to coarse-grain consistently at O(grad^4) requires a systematic procedure, based on multiple-scale analysis, to eliminate fast-evolving orientational moments. Using this, we calculate from microscopic physics all five coefficient functions of the active Cahn-Hilliard theory for tQSAPs. We identify contributions that were missed in previous continuum theories, and show how neglecting them becomes justified only in the limit of large quorum-sensing range parameter. Comparison with particle simulations of tQSAPs shows that our O(grad^4) theory improves on previous continuum models [...]
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All authors Sumeja Bureković, Filippo De Luca, Michael E. Cates, Cesare Nardini
Materials Science
Electronic structure, phase stability, and transport properties of the AlTiVCr lightweight high-entropy alloy: A computational study
Christopher D. Woodgate, Hubert J. Naguszewski, Nicolas F. Piwek et al. (+1 more)
We investigate the thermodynamics and phase stability of the AlTiVCr lightweight high-
entropy alloy using a combination of ab initio electronic structure calculations, a concentration wave analysis, and atomistic Monte Carlo simulations. In
alignment both with experimental data and with results obtained using other computational approaches, we predict a $\textrm{B2}$ (CsCl) chemical ordering emerging in this
alloy at comparatively high temperatures, which is driven by Al and Ti moving to separate sublattices, while V and Cr express weaker site preferences. The impact of this $\textrm{B2}$ chemical ordering on the electronic transport properties of the
alloy is investigated within a Kubo-Greenwood linear response framework and it is found that, counter-intuitively, the
alloy's residual resistivity increases as the material transitions from the $\textrm{A2}$ (disordered bcc) phase to our predicted $\textrm{B2}$ (partially) ordered structure. This is understood to result primarily from a reduction in the density of electronic states at the
Fermi level induced by the chemical ordering. At low temperatures, our atomistic Monte Carlo simulations then reveal subsequent sublattice orderings, with the ground-state configuration predicted to be a fully-ordered, single-phase structure with vanishing associated residual resistivity. These results give fresh, insight into the atomic-scale structure and consequent physical properties of this well-studied, technologically relevant material.
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All authors Christopher D. Woodgate, Hubert J. Naguszewski, Nicolas F. Piwek, David Redka
Materials Science
Mobile charges in MoS2/high-k oxide transistors: from abnormal instabilities to memory-like dynamics
Shaokai Zhou, Haihui Cai, Yehao Wu et al. (+6 more)
MoS$_2$ field-effect transistors (FETs) with high-k
oxides currently lag behind silicon standards in bias and temperature stability due to ubiquitous border
oxide traps that cause clockwise (CW) hysteresis in gate transfer characteristics. While suppressing this effect is typically mandatory for logic FETs, here we explore an alternative strategy where the initial CW hysteresis can be dynamically overcome by stronger counterclockwise (CCW) hysteresis towards
memory-like dynamics. We systematically compare hysteresis in similar back-gated MoS$_2$/HfO$_2$ and MoS$_2$/Al$_2$O$_3$ FETs up to 275\textdegree C. At room temperature, both devices initially show sizable CW hysteresis. However, at 175\textdegree C MoS$_2$/HfO$_2$ FETs exhibit dominant CCW dynamics coupled with self-doping and negative differential resistance (NDR) effects. Our compact model suggests that this behavior is caused by the drift of mobile oxygen vacancies (V\({}_{\mathrm{O}}^{+}\) or V\({}_{\mathrm{O}}^{2+}\)) within HfO$_2$ which also causes negative $V_{\mathrm{th}}$ shift under a constant positive bias stress. This alternative mechanism effectively overrides the initial CW hysteresis and enables intrinsic
memory functionality that can be enhanced by using narrower gate bias sweep ranges. In contrast, the MoS$_2$/Al$_2$O$_3$ FETs display only minor CCW dynamics even at 275\textdegree C due to higher drift activation energies for the same vacancies, thereby maintaining superior stability. Our results reveal an
insulators selection paradigm: Al$_2$O$_3$ layers are better suited to suppress detrimental negative $V_{\mathrm{th}}$ shifts in MoS$_2$ logic FETs at high temperatures, whereas their HfO$_2$ counterparts can serve as active
memory layers that would exploit these abnormal instabilities.
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All authors Shaokai Zhou, Haihui Cai, Yehao Wu, Yufeng Min, Renchen Yuan, Yezhu Lv, Jianming Huang, Yuanyuan Shi, Yury Yuryevich Illarionov
Strongly Correlated Electrons
Bosonization Solution to Spin-Valley Kondo Problem: Finite-Size Spectrum and Renormalization Group Analysis
Yi-Jie Wang, Geng-Dong Zhou, Hyunsung Jung et al. (+3 more)
Spin-valley Anderson
impurities (SVAIM) with (anti-)Hund's splitting provide a natural explanation to the origin of pairing potential and pseudogap in the magic-angle
graphene. In this work, we derive and analytically solve the low-energy Kondo theories for SVAIM at half-filling, with especial focus on the two anti-Hund's regimes: the
impurity is either dominated by a valley doublet, or a trivial singlet. In the doublet regime, we reveal that a novel pair Kondo scattering $\lambda_x$ is required to flip the valley doublet, which involves a quartic operator of bath electrons. Our renormalization group (RG) calculation based on the Coulomb gas analog shows $\lambda_x$ drives a phase transition of the Berezinskii-Kosterlitz-Thouless type. One side of the transition is an anisotropic doublet phase, characterized by non-universal phase shifts of bath electrons and non-analytic
impurity susceptibilities, while the other is a
Fermi liquid formed by pair-Kondo resonance. The finite-size many-body spectrum, thermodynamic quantities, and correlation functions for both phases are analytically solved. Remarkably, the solution in the pair-Kondo
Fermi liquid is achieved via the constructive approach of bosonization-refermionization along a solvable fixed line, where the many-body interaction $\lambda_x$ is mapped into a pseudo-
fermion bilinear in a rigorous manner. Finally, we also apply the RG analysis to the singlet regime, and identify a second-order phase transition between the Kondo
Fermi liquid and a local singlet phase.
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All authors Yi-Jie Wang, Geng-Dong Zhou, Hyunsung Jung, Seongyeon Youn, Seung-Sup B. Lee, Zhi-Da Song
Materials Science
Dielectric, magnetic and lattice dynamics properties of double perovskite (Ca0.5Mn1.5)MnWO6
Hong Dang Nguyen, Alexei A. Belik, Petr Kužel et al. (+7 more)
Recent dielectric and
magnetic studies of (Ca0.5Mn1.5)MnWO6 ceramics [A.A. Belik, Chem. Mater. 36, 7604 (2024)] have classified this material as a rare hybrid multiferroic, with both
antiferromagnetic and (anti)ferroelectric ordering occurring at the same temperature of 22 K. The pronounced dielectric anomaly observed at this temperature indicated that the structural change is primarily induced by a
phonon soft mode and not by a
spin arrangement, as is usually the case in type II multiferroics. However, our comprehensive investigation involving new ceramic samples as well as the sample from the above-mentioned reference does not support this conclusion. Low-temperature polarization measurements revealed no evidence of either ferroelectric or antiferroelectric order in both sample series. The dielectric permittivity exhibits only a slight change at the
antiferromagnetic transition, and
phonon modes observed in IR and Raman spectra show no indication of a
symmetry change at low temperatures. In the new samples the Neel temperature is shifted to TN = 18 K. XRD, SEM, EDS and WDS analyses confirmed the composition (Ca0.5Mn1.5)MnWO6 of both ceramics, but also indicated a small amount (percentage points) of MnO and CaO
impurities in the sample from the previous publication and Mn3O4, CaWO4 secondary phases (<4%) in the new ceramics. The differences in dielectric and
magnetic properties of the two samples can therefore be explained by their different chemical purity. The small dielectric anomaly of the new sample at the
antiferromagnetic transition temperature is explained by a
spin-
phonon coupling. We conclude that (Ca0.5Mn1.5)MnWO6 is not a multiferroic, but a paraelectric antiferromagnet.
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All authors Hong Dang Nguyen, Alexei A. Belik, Petr Kužel, Fedir Borodavka, Maxim Savinov, Jan Drahokoupil, M. Jarošová, Petr Proschek, Bartoloměj Vaníček, Stanislav Kamba
Materials Science · Cross-listed from math.NA
Numerical efficiency of explicit time integrators for phase-field models
Marco Seiz and Tomohiro Takaki
Phase-field simulations are a practical but also expensive tool to calculate microstructural
evolution. This work aims to compare explicit time integrators for a broad class of phase-field models involving coupling between the phase-field and concentration. Particular integrators are adapted to constraints on the phase-field as well as storage scheme implications. Reproducible
benchmarks are defined with a focus on having exact sharp interface solutions, allowing for identification of dominant error terms. Speedups of 4 to 114 over the classic forward Euler integrator are achievable while still using a fully explicit scheme without appreciable accuracy loss. Application examples include final stage sintering with pores slowing down grain growth as they move and merge over time.
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Materials Science
Electrically Accessible Metamagnetic Transition via a Doping-Induced Low-Energy Magnetic State in Antiferromagnetic Insulator RFeO3
Wanting Yang, Haohuan Peng, Ziming Wang et al. (+7 more)
Low-energy
antiferromagnetic phase transitions offer an appealing platform for low-power spintronic functionalities, yet their direct electrical access in insulating antiferromagnets remains challenging, particularly in the low-field regime where subtle Neeel vector reorientations dominate. Here, we demonstrate that targeted rare-earth-site engineering enables an electrically accessible metamagnetic transition in the insulating orthoferrite Ho0.5Dy0.5FeO3. By combining the distinct
spin-reorientation sequences of DyFeO3 and HoFeO3, Dy substitution stabilizes a dual
spin-reorientation pathway, hosting an intermediate state with a reduced energy barrier. This low-energy
antiferromagnetic state can be tuned into the weak-
ferromagnetic state under low
magnetic fields. The critical field decreases with increasing temperature, providing a favorable window for functional manipulation. Both longitudinal and transverse
spin Hall magnetoresistance channels exhibit clear and reproducible signatures of the metamagnetic transitions. Owing to the enhanced sensitivity of the transverse channel, additional low-field features are resolved, reflecting the projection of the Neel vector onto the
spin-accumulation direction. Electrical transport measurements correlate directly with the magnetically determined phase boundaries, establishing a purely electrical access to low-energy phase transitions and to illustrate a viable pathway for exploring low-power
spin dynamics in insulating
oxide antiferromagnets.
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All authors Wanting Yang, Haohuan Peng, Ziming Wang, Xiaoxuan Ma, Baojuan Kang, Chang Xue, Rongrong Jia, Jun-Yi Ge, Jinrong Cheng, Shixun Cao
Mesoscale and Nanoscale Physics
A low-tech solution to process entire metal/molecule heterostructure stacks into vertical nanopillar electronic devices
T. Zafar, L. M. Kandpal, E. Urbain et al. (+12 more)
Quantum technologies aim to assemble devices whose operation is controlled by the
quantum state of individual atoms. Achieving this level of control in a practical, scalable design remains, however, a major obstacle to mass societal adoption. By working at the level of interatomic bonding, molecular engineering has enabled exquisite control over the electronic properties of individual atoms and their interactions with neighboring atoms. This positions molecular electronics as a potentially disruptive
quantum technology, but serious technological challenges have prevented it from being included in technical road maps. The main obstacle is that conventional, mass scalable nanodevice technologies utilize resists and solvents that can degrade molecules. Some approaches involve exposing junction interfaces to contaminants (e.g. air, resist etc...), which can be particularly problematic for spintronics. In this technical paper, we present our decade-long work into building a nanotechnological chain that can process entire metal/molecule
heterostructures into vertical nanopillars electronic devices. We discuss the advantages and pitfalls of the various iterations of this process that were implemented. We also discuss outlooks for this unique technology.
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All authors T. Zafar, L. M. Kandpal, E. Urbain, N. Beyer, B. Gobaut, L. Joly, H. Majjad, S. Siegwald, D. Mertz, B. Leconte, C. Kieber, V. Da Costa, W. Weber, S. Boukari, M. Bowen
Superconductivity
Superconductivity in non-centrosymmetric rhombohedral NbSe2
Zhengxian Li, Xiaoyu Shen, Kai Liu et al. (+14 more)
Crystal stacking offers a powerful yet underexplored route to engineer
symmetry in layered
superconductors. Here we report superconductivity in rhombohedral-stacked NbSe2 (3R-NbSe2), a non-centrosymmetric polytype in which global inversion
symmetry is removed by stacking alone. Using comprehensive structural, transport,
magnetic, and thermodynamic measurements, we establish superconductivity as a bulk property of the 3R phase and find that the in-plane upper critical field exceeds the Pauli paramagnetic limit, indicating the persistence of strong Ising-type
spin-orbit coupling. Unlike the thickness-dependent superconductivity in centrosymmetric 2H-NbSe2, the superconducting transition temperature in 3R-NbSe2 shows little dependence on layer number but exhibits an unusually strong sensitivity to disorder. We further observe strongly enhanced nonlinear optical and electrical responses near the superconducting transition, consistent with stacking-induced inversion-
symmetry breaking. Our results identify 3R-NbSe2 as a single-phase platform in which stacking engineering reshapes superconductivity and enables nonlinear transport phenomena in layered materials.
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All authors Zhengxian Li, Xiaoyu Shen, Kai Liu, Yating Sha, Tianyang Wang, Feng Liu, Qingchen Duan, Kenji Watanabe, Takashi Taniguchi, Peng Chen, Shiyong Wang, Ruidan Zhong, Dong Qian, Shengwei Jiang, Yufan Li, Noah F. Q. Yuan, Guorui Chen
Materials Science
Simulations of High Temperature Decomposition of Metal-Organic Frameworks to form Amorphous Catalysts
Connor W. Edwards, Oliver M. Linder-Patton and Jack D. Evans
Metal-organic framework (MOF) derived materials formed through high temperature processes show great potential as catalysts. However, understanding of structure-property relationships between the initial MOF and the resulting MOF-derived catalyst is limited because the amorphous nature of the catalyst challenges standard structural characterization methods. Neural network approaches that learn interatomic potentials from density functional theory offer a promising solution. We simulated the pyrolysis of UiO-66, UiO-67 and MIP-206 using both foundational and fine-tuned machine learned interatomic potentials (MLIPs). To mimic experimental conditions, an atmosphere of CO2 and H2 was introduced and the structures were doped with 20 wt% copper to probe the effect of copper on the structural
evolution of MOFs. These simulations provide atomistic insights into gas
evolution, metal nanoparticle formation, and linker decomposition that were compared to available experimental data. Overall, this work demonstrates the potential of MLIPs to accurately model high temperature MOF dynamics under experimentally relevant conditions and guide the design of new catalytic materials.
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Statistical Mechanics · Cross-listed from quant-ph
Gluing Randomness via Entanglement: Tight Bound from Second Rényi Entropy
Wonjun Lee, Hyukjoon Kwon and Gil Young Cho
The efficient generation of random
quantum states is a long-standing challenge, motivated by their diverse applications in
quantum information processing tasks. In this work, we identify
entanglement as the key resource that enables local random
unitaries to generate global random states by effectively gluing randomness across the system. Specifically, we demonstrate that approximate random states can be produced from an entangled state $|\psi\rangle$ through the application of local random
unitaries. We show that the resulting ensemble forms an approximate state design with an error saturating as $\Theta(e^{-\mathcal{N}_2(\psi)})$, where $\mathcal{N}_2(\psi)$ is the second Rényi
entanglement entropy of $|\psi\rangle$. Furthermore, we prove that this tight bound also applies to the second Rényi
entropy of coherence when the ensemble is constructed using coherence-free operations. These results imply that, when restricted to resource-free gates, the quality of the generated random states is determined entirely by the resource content of the initial state. Notably, we find that among all $\alpha$-Rényi entropeis, the second Rényi
entropy yields the tightest bounds. Consequently, these second Rényi
entropies can be interpreted as the maximal capacities for generating randomness using resource-free operations. Finally, moving beyond approximate state designs, we utilize this
entanglement-assisted gluing mechanism to present a novel method for generating pseudorandom states in multipartite systems from a locally entangled state via pseudorandom
unitaries in each of parties.
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Strongly Correlated Electrons
Effect of Electron Correlation on the Integer Quantum Hall Effect
Daniel Staros, Christopher Lane, Roxanne Tutchton et al. (+1 more)
We numerically investigate the effect of electron correlation on the integer
quantum Hall effect in a square
lattice. Increasing the correlation strength via the effective onsite repulsion parameter $U$ degrades the quantization of $\nu = 1$ transverse conductance due to the interplay of correlation and the external
magnetic field, which together induce periodic modulations in renormalized hopping parameters and site energies. Overall, this work demonstrates that the strength of electron correlation can significantly impact conductivity in the integer
quantum Hall regime.
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All authors Daniel Staros, Christopher Lane, Roxanne Tutchton, Jian-Xin Zhu
Mesoscale and Nanoscale Physics
Distinguishing Hot-Electron and Optomechanical Pathways at Metal-Molecule Interfaces
Bing Gao, Jameel Damoah, Wassie M. Takele et al. (+1 more)
Energy and charge transfer between molecules and metal surfaces underpin heterogeneous catalysis, surface-enhanced spectroscopies and plasmon-driven chemistry, yet the microscopic origins of vibrational excitation at metal interfaces remain unresolved. Here we use temperature-dependent surface-enhanced Raman scattering (SERS) to directly distinguish plasmon-vibration optomechanical coupling from hot-electron-driven excitation.By probing thionine adsorbed on gold nanostructures at 295 K and 3.5 K, we show that pronounced anti-Stokes scattering at cryogenic temperature arises from optical pumping of vibrational populations, whereas room-temperature spectra are governed by thermal population. Bromide co-adsorbates play a decisive role by guiding molecular
alignment, inducing surface atom displacements, and enabling transient adsorption geometries that activate otherwise Raman-inactive vibrational modes. In the absence of bromide, distinct excitation pathways emerge, reflecting competition between optomechanical coupling and charge-transfer processes associated with molecular polarization along the optical field or orientation relative to the metal surface. These results establish molecular optomechanics as a sensitive probe of surface-molecule interactions and demonstrate how anion-mediated surface dynamics regulate energy flow at plasmonic interfaces.
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All authors Bing Gao, Jameel Damoah, Wassie M. Takele, Terefe G. Habteyes
Soft Condensed Matter
Active Particles Destabilize Passive Membranes
David A. King, Thomas P. Russell and Ahmad K. Omar
We present a theory for the interaction between active particles and a passive flexible membrane. By explicitly solving for the pressure exerted by the active particles, we show that they reduce the membrane tension and bending modulus and introduce novel non-local contributions to the membrane mechanics. This theory predicts activity-induced instabilities and their morphology are in agreement with recent experimental and simulation data.
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Materials Science
Anharmonic thermodynamics redefines metastability and parent phases in ferroelectric HfO2
Yiheng Shen, Chang Liu, Wei Xie et al. (+1 more)
Hafnia (HfO2) is a silicon-compatible dielectric material, yet stabilizing its desired but metastable ferroelectric phase remains challenging. Phase stability predictions by density functional theory (DFT) have provided crucial guidance, but most simulations neglected or only treated finite temperature effects with (quasi-)harmonic approximation due to high computational cost of DFT. Here, we develop a machine learning force field and perform thermodynamic calculations for HfO2 using self-consistent
phonon theory to address growing evidence of anharmonicity. Our results reveal that the ferroelectric orthorhombic phase oIII exhibits metastability below 0.1kBT under most conditions within the simulated regime of temperature and pressure (600 K <= T <= 1500 K and 0 <= p <= 7.5 GPa), contradicting previous harmonic predictions of metastability above 1500 K at ambient pressure. We further report evidence for temperature- and pressure-dependent ferroelectric parent phase despite efforts to identify a universal one. This study highlights the importance of anharmonicity and provides an effective approach for its treatment in the design of HfO2-based ferroelectrics.
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All authors Yiheng Shen, Chang Liu, Wei Xie, Wei Ren
Materials Science
Photoinduced metastable cation disorder in metal halide double perovskites
Shunran Li, Burak Guzelturk, Conrad A. Kocoj et al. (+18 more)
Lead-free perovskites have emerged as environmentally benign alternatives to lead-halide counterparts for optoelectronics. Among them, the double perovskite Cs2AgInCl6 family exhibits remarkable white-light emission with proper composition engineering, enabled by strong electron-
phonon coupling and the formation of self-trapped
excitons (STEs). Despite these advantages, the fundamental photo- and structural dynamics governing their excited-state behavior remain poorly understood. Here, we report a long-lived metastable phase in the Cs2AgInCl6 double perovskite family and unravel this process and the concomitant electronic and structural
evolution using a suite of tools including transient optical spectroscopy, time-resolved X-ray diffraction (TR-XRD) and X-ray absorption (TR-XAS). We show that the photoinduced, transient metastable phase is associated with B-site (Ag-In) disorder, which induces a dramatically reduced optical bandgap. Supported by TR-XRD and first-principles calculations, the Ag-In disorder drives the formation of Ag-rich and In-rich domains with millisecond lifetimes, with lifetimes increasing at lower temperatures. TR-XAS further reveals that photogenerated STEs oxidize Ag+ to Ag2+, facilitating this highly temporally asymmetric order-disorder transition. Our findings demonstrate a new mechanism, mediated by hole-localized STE formation, that enables prolongation of transient light-induced states to the multi-millisecond regime in double perovskites, opening possibilities to harvesting the functional properties of metastable phases of these materials.
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All authors Shunran Li, Burak Guzelturk, Conrad A. Kocoj, Donald A. Walko, Du Chen, Haidan Wen, Xian Xu, Xiaoming Wang, Bongjun Choi, Borui Li, Zhibo Kang, Cunming Liu, Suchismita Sarker, Benjamin T. Diroll, Xiaoyi Zhang, Yong Q. Cai, Yu He, Deep Jariwala, Yanfa Yan, Diana Y. Qiu, Peijun Guo
Mesoscale and Nanoscale Physics
Diffusive and hydrodynamic magnetotransport around a density perturbation in a two-dimensional electron gas
P. S. Parashar and M. M. Fogler
We study current flow around a density inhomogeneity in a two-dimensional electron gas in the presence of a strong
magnetic field. The inhomogeneity is parametrized by a power-law tail with an exponent $\beta > 2$. We show that current and electrochemical potential are exponentially suppressed inside a surrounding area much larger than the
geometric size of the perturbation. The corresponding “no-go” radius grows as a certain power of the
magnetic field. Residual current and potential exhibit spiraling patterns inside the no-go region. Outside of it, they acquire corrections inversely proportional to the distance, which is known as the Landauer resistivity dipole. The Landauer dipole is rotated by the angle $\pi (1 - 1 / \beta)$ with respect to the average electric field. The rotation direction depends on whether the local density is raised or lowered. We also consider the effect of electron viscosity and show that the variation of the no-go radius with
magnetic field becomes more rapid if viscosity is large enough. The Landauer dipole size is set by the Gurzhi length, which is much larger than the no-go radius, which is in turn much larger than the
geometric size of the perturbation. Our results may be useful for interpreting nanoimaging of current distribution in
graphene and other two-dimensional systems.
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Strongly Correlated Electrons
Accelerating dynamical mean-field theory convergence by preconditioning with computationally cheaper quantum embedding methods
E. M. Makaresz, O. Gingras, Tsung-Han Lee et al. (+3 more)
Dynamical mean-field theory (DMFT) is a cornerstone technique for studying strongly correlated electronic systems. However, each DMFT step is computationally demanding, and many iterations can be required to achieve convergence. Here, we accelerate the convergence of DMFT by initializing its self-consistent cycle with solutions from computationally cheaper and more approximate methods. We compare the initialization with the non-interacting solution to a range of
quantum embedding compatible approaches: Hartree-Fock, the Hubbard-I approximation, rotationally invariant slave
bosons (RISB), and its ghost extension (g-RISB). We find that these initializations can reduce the number of DMFT iterations by up to an order of magnitude, with g-RISB providing the most effective and reliable benefits. In most regimes, initializing with g-RISB and performing a single DMFT iteration suffices to recover the full dynamical structure. The improvement in convergence is controlled by the initial solution's accuracy in the low-energy part of the self-energy, on the scale of the non-interacting bandwidth. This strategy is especially effective at the Mott
insulator-metal transition, where an initialization from the non-interacting limit can lead to a breakdown of DMFT due to the sign problem. Our results establish the usage of accurate yet cheaper
quantum embedding methods as a powerful means to substantially reduce the computational cost of DMFT, particularly in regimes where convergence is slow or prone to failure.
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All authors E. M. Makaresz, O. Gingras, Tsung-Han Lee, Nicola Lanatà, B. J. Powell, Henry L. Nourse
Strongly Correlated Electrons
Realization of a triangular spin necklace in a verdazyl-based Ni complex
Itsuki Shimamura, Risa Yagura, Takanori Kida et al. (+6 more)
We successfully synthesized a verdazyl-based complex, ($m$-Py-V)$_3$[Ni(NO$_3$)$_2$], in which Ni$^{2+}$ ions and verdazyl radicals form a one-dimensional, triangular
spin necklace consisting of
spin-1/2 and
spin-1 units. Molecular orbital calculations reveal strong
antiferromagnetic (AF) interactions between inversion-related radical pairs that form
spin-1/2 singlet dimers. The remaining verdazyl and Ni$^{2+}$
spins form frustrated triangular units, creating a distinctive
spin network.
Magnetic susceptibility and specific heat measurements identify a phase transition to an AF order. The application of
magnetic fields suppresses the phase transition signal, suggesting field-induced decoupling of the
spin-1 moments. Electron
spin resonance measurements are used to evaluate the easy-axis anisotropy of
spin-1, which may promote the AF order. This work provides a rare example of a geometrically frustrated
quantum spin chain realized via molecular design, thereby offering a platform for exploring frustration-driven
quantum phases in low-dimensional materials.
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All authors Itsuki Shimamura, Risa Yagura, Takanori Kida, Masayuki Hagiwara, Koji Araki, Yoshiki Iwasaki, Yuko Hosokoshi, Kenta Kimura, Hironori Yamaguchi
Strongly Correlated Electrons
Emergence of Kondo-assisted Néel order in a Kondo necklace model
Hironori Yamaguchi, Shunsuke C. Furuya, Yu Tominaga et al. (+3 more)
The interplay between Kondo screening and
magnetic order has long been a central issue in the physics of strongly correlated systems. While the Kondo effect has traditionally been understood to suppress magnetism through the formation of local singlets, recent studies suggest that Kondo interactions may enhance
magnetic order under certain conditions. However, these scenarios often rely on complex electronic structures, including orbital and charge degrees of freedom, making the essential mechanisms difficult to isolate. Here we report the realization of a
spin-(1/2,1) Kondo necklace model in a Ni-based complex-a minimal
spin-only analog of the Kondo
lattice that isolates
quantum spin correlations by eliminating charge degrees of freedom. Thermodynamic measurements identify a
magnetic phase transition and a field-induced
quantum phase transition. Perturbative analysis reveals that the Kondo coupling mediates effective
antiferromagnetic interactions between the
spin-1 sites, stabilizing the Néel order across the entire chain. Our results establish a universal boundary in Kondo physics, where coupling to
spin-1/2 moments yields singlets, but to
spin-1 and higher stabilizes
magnetic order.
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All authors Hironori Yamaguchi, Shunsuke C. Furuya, Yu Tominaga, Takanori Kida, Koji Araki, Masayuki Hagiwara
Statistical Mechanics
Fluctuation-Response Theory for Nonequilibrium Langevin Dynamics
Hyun-Myung Chun, Euijoon Kwon, Hyunggyu Park et al. (+1 more)
We establish a unified fluctuation-response relation for Langevin dynamics. By exploiting the common mathematical structures underlying fluctuations and responses of empirical density and current, we derive a unified identity that generalizes the fluctuation-dissipation
theorem from
equilibrium to nonequilibrium settings. This relation connects global fluctuations of observables with their local responses to perturbations in force, mobility, and temperature. We further derive finite-time fluctuation-response inequalities, leading to response uncertainty relations that complement the identity by providing more practical bounds. These derivations establish a unified theoretical framework linking the fluctuation-dissipation
theorem and thermodynamic uncertainty relations. Using the $F_1$-ATPase molecular motor model, we illustrate how these response-based bounds constrain the long-time
diffusion coefficient.
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All authors Hyun-Myung Chun, Euijoon Kwon, Hyunggyu Park, Jae Sung Lee
Strongly Correlated Electrons
Ab Initio Many Body Quantum Embedding and Local Correlation in Crystalline Materials using Interpolative Separable Density Fitting
Junjie Yang, Ning Zhang, Shunyue Yuan et al. (+3 more)
We present an efficient implementation of ab initio many-body
quantum embedding and local correlation methods for infinite periodic systems through translational
symmetry adapted interpolative separable density fitting, an approach which reduces the scaling of the calculations to only linear with the number of k-points. Employing this methodology, we compute correlated ground-state coupled cluster energies within density
matrix embedding and local natural orbital correlation frameworks for both weakly and strongly correlated solids, using up to 1000 k-points. By extrapolating the local correlation domains and k-point sampling we further obtain estimates of the full coupled cluster with singles, doubles, and perturbative triples ground-state energies in the thermodynamic limit.
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All authors Junjie Yang, Ning Zhang, Shunyue Yuan, Jincheng Yu, Hong-Zhou Ye, Garnet Chan
Materials Science
Energy Eigenstates of Electrons, Magnons and Phonons in Fe$_3$O$_4$ (magnetite), MnFe$_2$O$_4$ (jacobsite), and mixed Mn-Zn ferrites
Deepak Dhariwal, Michael R. von Spakovsky and William T. Reynolds Jr
We report first-principles calculations of the electronic structure,
magnon excitations, and
phonons in magnetite (Fe$_3$O$_4$), jacobsite (MnFe$_2$O$_4$), and mixed manganese-zinc ferrites (Mn$_{x}$,Zn$_{1-x}$)Fe$_2$O$_4$ for representative compositions ($0\le x \le 1$) and A/B-site cation arrangements. Electronic structures are computed using density functional theory (DFT) augmented by rotationally invariant DFT+U+J, with on-site Hubbard and Hund's parameters, $U$ and $J$, respectively, determined self-consistently by
spin-polarized linear-response perturbations of the chosen correlated subspaces (including, where applied, the ligand $2p$ subspace). A classical Heisenberg
spin Hamiltonian is parameterized by mapping DFT+U+J total energies for multiple collinear
spin configurations onto nearest-neighbor exchange couplings, which are then used to obtain
magnon dispersions and
magnon densities of states within linear
spin-wave theory.
Phonon spectra and densities of states are obtained from finite-displacement force constants and dynamical
matrices computed on the same DFT+U+J-relaxed structures. Overall, the workflow provides a consistent, composition- and configuration-aware route to electronic, vibrational, and
magnetic excitation spectra across the Mn/Zn ferrite space.
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