CMP Journal 2026-10-26
Statistics
Nature Physics: 1
Nature Reviews Materials: 2
arXiv: 80
Research Square: 1
Nature Physics
Three-dimensional cell morphology is mediated by curvature sensing and interfacial stress
Original Paper | Biophysics | 2026-10-25 20:00 EDT
Yi Liu, Baoce Sun, Shuhuan Hu, Ngoc Luu, Jifeng Ren, Lelin Liu, Jingqian Zhang, Yun Qu, Ruolin Zhang, Jialei Song, Mo Yang, Ao Zhou, Hanbai Wu, Dong Sun, Jinlian Hu, Denvid Lau, Weiqiang Chen, Raymond H. W. Lam
Curvature sensing of cells critically governs three-dimensional cell morphology, which is integral to tissue and organ development as well as the wound-healing processes. However, the underlying mechanism by which sensing occurs remains unclear. Here we investigate the physical principles that govern curvature sensing at both single-cell and monolayer levels. We find that the cell-substrate interfacial stress ratio–defined as the balance between the cell contractile stress and the cell-substrate adhesion stress–determines the two predominant three-dimensional cell morphology modes, namely, complete adhesion and partial interior detachment. When the interfacial stress ratio is much higher than unity, a rapid morphological shift from complete adhesion to partial interior detachment occurs. This process is irreversible, as it proceeds towards a lower-energy state. We observe this mode switching for various cell types, under pharmacological perturbations and across multicellular layers, offering a universal biophysical framework for regulating three-dimensional cell morphology.
Biophysics, Motility, Biological physics
Nature Reviews Materials
Programmable mRNA vaccine materials for temporal control of antitumour immunity
Review Paper | Biomaterials - vaccines | 2026-10-25 20:00 EDT
Seong Dong Jeong, Chaoyang Tang, Xiaotian Wang, Antoni J. Szeglowski, Yujin Kim, B. J. Kim, Padmanee Sharma, James J. Moon, Wen Jiang, Betty Y. S. Kim
Advances in mRNA and nanomaterial design have transformed vaccine technology, enabling precise control of antigen expression, delivery kinetics and immune activation. However, several leading clinical-stage mRNA cancer vaccine programmes are being evaluated in the adjuvant setting, in which loss of the primary tumour antigen reservoir and evolving postoperative immune states may alter the conditions for effective priming. Here, we present a materials-driven framework for temporal immunoengineering, in which programmable mRNA vaccine materials are designed to align antigen availability, innate sensing and adaptive priming with changing immune states across the perioperative window. Using the perioperative period as an illustrative model of immune flux, we discuss how distinct mRNA nanocarrier architectures can be engineered to tune the timing, magnitude and anatomical context of innate activation, antigen expression and adaptive priming. A universal neoadjuvant mRNA ‘prime’, formulated in an immunostimulatory nanocarrier, could condition innate and myeloid compartments and remodel the tumour microenvironment, whereas a personalized adjuvant ‘boost’, delivered in translationally efficient formulations, could reinforce clonal expansion and memory of tumour-specific T cells. By treating biomaterials as programmable regulators of immunodynamics rather than passive carriers, this Perspective establishes temporal control as a complementary design axis for next-generation mRNA vaccine systems.
Biomaterials - vaccines, DNA and RNA, Nanotechnology in cancer, Cancer immunotherapy, RNA vaccines
Decoding the risks of hydrogels for bone regeneration
Review Paper | Bioinspired materials | 2026-10-25 20:00 EDT
Yuxuan Li
(李俣璇), Yunkai Tang
(汤云开), Wenguo Cui
(崔文国)
Engineered hydrogels provide hydrated, tunable and biointeractive matrices for bone regeneration, but few have advanced from preclinical promise to defined clinical indications. This translational gap reflects application-specific failure in dynamic bone microenvironments rather than a lack of material innovation alone. In this Review, we decode hydrogel risks across craniofacial filling, long-bone reconstruction, osteochondral repair, local drug delivery, cell delivery, implant coating and oral modulation of metabolic bone disease. We organize these failures into mechanical gap, spatiotemporal mismatch and immune dysregulation and further identify emerging long-term and systemic risks. Finally, we position experimental hydrogels against clinical products, manufacturability constraints and large-animal benchmarks to propose risk-controlled design principles for next-generation bone-regenerative hydrogels.
Bioinspired materials, Biomedical materials
arXiv
Lattice Symmetry Remnants in Spatial and Temporal Entanglement of Quantum Critical Spin Chains
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-10-26 20:00 EDT
Quantum critical lattice models carry universal information beyond the bulk data of their infrared conformal field theory (CFT): microscopic lattice symmetries constrain how the CFT is realized. We probe these remnants through the spatial and temporal entanglement of two Euclidean-evolved states from the same critical model. In the finite-length scaling regime, a conformal boundary encodes the long-distance effect of the short-range initial state, and boundary CFT (BCFT) organizes the universal low-lying entanglement spectrum. We formulate the temporal state as a uniform infinite matrix product state evolved by a symmetry-preserving infinite matrix product operator, using a local factorization regular even at arbitrarily small Trotter steps. For the Ising and three-state Potts chains, whose relevant symmetries are onsite, the spatial and temporal constructions approach the same BCFT structure; varying the initial state engineers conformal boundaries distinguishable spectroscopically. The spin-1/2 XXZ chain instead realizes a Lieb–Schultz–Mattis (LSM) constraint between internal U(1) symmetry and one-site translation. A U(1)-preserving short-range spatial state accommodates it through a doubled unit cell and inequivalent entanglement cuts, whereas the temporal state remains uniform along Euclidean time. Successive spatial transfer steps pump the temporal entanglement spectrum between translation-related Dirichlet sectors, equivalently between integer and half-integer compact-boson zero modes. Breaking U(1) removes both the zero mode and the alternation. Continued evolution at fixed bond dimension crosses over from the finite-length BCFT regime to a finite-entanglement regime generated by symmetry-allowed relevant deformations. Thus microscopic symmetry and anomaly data remain visible in universal entanglement by constraining the boundary realization of the infrared CFT.
Strongly Correlated Electrons (cond-mat.str-el)
Phonon evidence for a partial, re-entrant spin reorientation near room temperature in LaFe$_{1-x}$Ni$_x$O$_3$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Subha Maity, Dushyant Singh, Vigneshwari S R, Tharundev V V, Navneet Sharma, Subhavenkadesh SS, Krista R. Khiangte
Spin reorientation near room temperature offers a route to controlling antiferromagnetic order, yet LaFeO$ 3$ , which lacks a magnetic rare-earth ion, is generally expected to retain its spin orientation along the $ a$ axis below $ T{\mathrm N}\approx740$ K. Here, we investigate LaFe$ _{1-x}$ Ni$ _x$ O$ _3$ ($ x=0$ and 0.1) using temperature-dependent magnetization and Raman spectroscopy over 200–400K. Both compositions exhibit magnetic anomalies at 285.6 and 323K, respectively, accompanied by correlated deviations of 12 Raman modes from their conventional anharmonic behavior. Principal component analysis and a global fitting approach reveal a common temperature-dependent phonon response, with mode-dependent amplitudes and signs. To interpret these anomalies, we develop a Landau-based spin-phonon coupling model describing complete, partial re-entrant, and incipient spin reorientation. Comparison with the experimental Raman profiles favors a partial, re-entrant rotation of the N’eel vector in both compositions, centered near 290K. Ni substitution narrows the characteristic reorientation interval from approximately 116 to 84K and enhances the magnetization anomaly by a factor of four. An additional feature near 262K in LaFeO$ _3$ is consistent with the Morin transition of trace $ \alpha$ -Fe$ _2$ O$ _3$ . These findings suggest that partial spin reorientation can emerge without magnetic rare-earth ions and establish collective Raman phonon anomalies as a sensitive indirect probe of magnetic anisotropy changes in orthoferrites.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Nonadiabatic vibrational dynamics of CO on Pt(111) studied with first-principles many-body perturbation theory
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Raúl Bombín, Iñaki Fernández Tena, J. Iñaki Juaristi, Maite Alducin
We investigate the nonequilibrium vibrational dynamics of CO adsorbed on Pt(111), a prototypical adsorbate-surface system for ultrafast vibrational spectroscopy, using a first-principles framework that combines many-body perturbation theory with density functional theory. Within this methodology we explicitly account for electron-hole pair excitations and electron-mediated phonon-phonon coupling. For the latter mechanism, we evaluate the vertex-correction screening, what constitutes a methodological novelty. Our calculations qualitatively reproduce the transient evolution of the internal stretch vibrational mode observed in femtosecond pump-probe experiments, allowing us to identify in the experimental measurements a small transient blueshift after excitation with a femtosecond laser pulse. As predicted in a previous work, the reduction in the number of electronic states available for electron-phonon coupling when the electronic temperature raises at a group 10 transition metal surface, effectively screens the electron-phonon interaction giving rise to an anomalous transient blue-shift.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
7 figures, 1 table
Altermagnetism in Folded Iron Chain Systems
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Ling-Fang Lin, Yang Zhang, Satoshi Okamoto, Adriana Moreo, Lun-Hui Hu, Elbio Dagotto
Altermagnetism, a moment-compensated magnetism with momentum-dependent spin splitting, has so far been realized primarily in Néel-type antiferromagnets. Here, we demonstrate altermagnetism in folded iron-chain systems with block-type magnetic order (e.g., $ \uparrow \uparrow \downarrow \downarrow$ ). In the strictly one-dimensional (1D) case, altermagnetism is forbidden by the $ [C_2||{\cal T}]$ symmetry, but it can emerge when such chains are stacked into a quasi-1D array. To generate altermagnetic spin splitting via this chain-stacking mechanism, two essential ingredients are required: a block-type spin order that spontaneously breaks the combined parity-time reversal symmetry, and finite inter-chain hopping. Using first-principles calculations, we identify the K$ _3$ Fe$ _2$ Se$ 4$ family as a promising platform that realizes this mechanism, hosting a $ d$ -wave altermagnet even without lattice $ C{4}$ symmetry. Moreover, owing to its lower symmetry, the block-type folded chain exhibits an isotropic altermagnetic spin splitting, which may manifest as an altermagnetic wrapping effect. Our findings unify real-space block magnetism and reciprocal-space altermagnetism, establishing folded iron chains as a tunable platform for zero-moment spintronic applications.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
9 Pages 5 figures
Phys. Rev. Lett. 137, 176702 (2026)
Thermoelectric properties and modulation doping of ultrawide-bandgap nitride monolayers
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Two-dimensional III-nitride alloys provide a composition-tunable platform for exploring thermoelectric transport and intrinsic electric-field tolerance. We combine first-principles electronic-structure calculations with semiclassical transport for ordered monolayer B$ _{x}$ Al$ _{1-x}$ N and B$ _{x}$ Ga$ _{1-x}$ N. State-dependent momentum relaxation times computed with AMSET include acoustic deformation-potential and piezoelectric scattering. Using a common, temperature-independent lattice thermal conductivity of 550 W/mK, we predict maximum thermoelectric figure of merit ZT>2.5 for selected p- and n-type monolayers and ZT>2 at 300~K for n-type B$ _{0.25}$ Ga$ _{0.75}$ N. Composition-dependent band curvature, screening, and scattering help interpret the different p- and n-type responses. Vacuum-referenced band alignments identify candidate modulation-doping partners for both carrier types; explicit hGaN/V$ _2$ O$ _5$ calculations yield a hole surface density of approximately 1.6$ \times10^{14}$ cm$ ^{-2}$ . A separate phenomenological model using the band gap and maximum phonon frequency predicts intrinsic breakdown fields of 20.06 and 20.74 MVcm for the Al- and Ga-containing x=0.75 alloys, respectively. These results motivate further investigation for thermoelectric and high-field power-electronic applications. The ZT values apply to the specified scattering and lattice-conductivity models, while the breakdown estimates require validation for monolayers and do not resolve field direction.
Materials Science (cond-mat.mtrl-sci)
Low-energy collective electronic excitations in a gold monolayer
New Submission | Other Condensed Matter (cond-mat.other) | 2026-10-26 20:00 EDT
Vyacheslav M. Silkin, Maxim Yu. Kagan
The low-energy plasmonic properties of a free-standing Au(111) monolayer, frequently referred to as goldene, are investigated by time-dependent density functional theory in the random phase approximation. In the evaluation of dielectric and loss functions the first-principle band structure characterized by a single $ s-p$ energy band at the Fermi level is taken into account. In this system with apparently simple band structure around the Fermi surface the calculations show the presence, besides the standard two-dimensional (2D) plasmon mode, at even lower energies of three anomalous branches in the momentum-energy region usually assigned to incoherent electron-hole pairs. This is an unexpected result since the electronic system of the gold monolayer is characterized by a single energy band crossing the Fermi level. The dispersion of these anomalous plasmonic branches is strongly anisotropic in-plane and gapless. A general feature is that at small in-plane momentum transfers the modes have a sound-like dispersion in certain momentum directions. We rely the appearance of these anomalous modes to a notable deviation of the Fermi surface of a gold monolayer from a circular shape. As a result of its almost perfect hexagon shape, there is possibility to realize in a {\it single} electronic energy band a scenario of a multi-component electron system with the carrier groups moving with different Fermi velocities in certain momentum directions. The found modes correspond to the out-of-phase charge oscillations of the carriers at different sides of the hexagonal Fermi surface. Hence our work presents evidence how in a metal system with apparently simple band structure around the Fermi level its shape can result in conversion of single-particle charge excitations into collective charge excitations.
Other Condensed Matter (cond-mat.other), Materials Science (cond-mat.mtrl-sci)
12 pages, 13 figures
Unifying Low-Frequency Raman and Infrared Signatures across Perovskites
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Ethan Berger, Erik Fransson, Apinya Ngoipala, Lucas Svensson, Priyanka Deswal, Mehmet Baskurt, Paul Erhart, Julia Wiktor
Perovskites have been studied for a wide range of applications, from oxide-based ferroelectrics to halide-perovskite photovoltaics. Despite their diverse functionalities, these materials share strong lattice anharmonicity arising from structural instabilities such as polar off-centering and octahedral tilting. These anharmonic distortions strongly influence the low-frequency vibrational response and can be observed in infrared (IR) and Raman spectra. However, low-frequency IR and Raman signatures are typically investigated separately, hindering the development of a unified understanding of vibrational spectroscopy across perovskite classes. In this work, we use machine-learning-based molecular dynamics to simulate the IR and Raman spectra of oxide perovskites (SrTiO$ _3$ and BaTiO$ _3$ ), halide perovskites (CsPbBr$ _3$ , CsSnBr$ _3$ , and CsGeBr$ _3$ ) and double halide perovskites (Cs$ _2$ AgAlBr$ _6$ and Cs$ _2$ AgBiBr$ _6$ ). By comparing materials exhibiting polar, tilt-driven and mixed instabilities, we find that polar off-centering leads to enhanced low-frequency IR and dielectric responses, whereas nonpolar modes, particularly octahedral tilting, are associated with Raman central peaks. The strength of the low-frequency features also depends on how strongly the underlying modes couple to polarization or dielectric susceptibility. Finally, we show that the dynamics of these instabilities play an important role, with slow polar reorientations shifting the dielectric response to very low frequencies and overdamped tilting modes producing persistent Raman central peaks. These results establish a unified framework connecting low-frequency IR and Raman spectra to the symmetry, coupling and dynamics of their underlying anharmonic lattice instabilities.
Materials Science (cond-mat.mtrl-sci)
Optical signatures of Rashba–Dresselhaus coupling across Franz–Keldysh and Landau regimes in two-dimensional semiconductors
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Bahruz Suleymanli, Samir Tariverdiev, B. Tanatar
We develop a unified theory of the interband optical response of a two-dimensional semiconductor with simultaneous Rashba and Dresselhaus spin-orbit couplings in electric and magnetic fields. In crossed fields, the in-plane electric field generates an effective spin-orbit drift field that modifies the Landau spectrum and spinor states, while at zero magnetic field the problem maps onto Landau–Zener spin this http URL zero external fields, the total joint density of states above the band gap remains unchanged, while characteristic subgap structures appear. Pure Rashba coupling produces an inverse square root singularity, whereas a finite Dresselhaus term gives a step and a logarithmic peak, allowing the two couplings to be distinguished optically. At zero magnetic field, the Franz–Keldysh response shows a crossover from diabatic to adiabatic spin dynamics as the electric field is reduced. In the weak-field Rashba regime, the field-free singularity becomes a finite peak whose height scales as $ \mathcal E^{-1/3}$ and whose position approaches $ E_g-E_{\rm SO}$ , providing a direct measure of the Rashba energy. In a perpendicular magnetic field, spin-orbit coupling shifts and splits the Landau absorption lines and produces anticrossings without changing their total weights. The Rashba splitting changes from a $ \sqrt{B}$ dependence at weak fields to a linear dependence at strong fields. Finally, in crossed electric and magnetic fields, the electric field broadens the Landau lines and drives a continuous crossover toward the Franz–Keldysh regime, while spin-orbit coupling produces opposite shifts and different widths for the two members of each doublet.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
‘Dancing’ two-dimensional patterns in nematics above the flexoelectric instability threshold
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-10-26 20:00 EDT
Various types of electrohydrodynamic instabilities in liquid crystals (LCs) are a recurring theme in LC research. The nonlinear stage of the flexoelectric instability in nematics remains the least studied aspect of this phenomenon. This work highlights a key advancement in nonlinear physics, providing a compelling example of nonlinear dynamical system behavior. By solving the system of nonlinear equations for a nematic in an alternating external field, we derive from first principles the unique “dancing” behavior of truly two-dimensional patterns above the flexoelectric instability threshold. Our analysis is restricted to liquid crystals with negative dielectric permittivity and electrical conductivity anisotropies. The resulting solution represents a stable limit cycle near above the Hopf bifurcation, valid within the parameters range where the solutions characteristic exponent is complex. The generalized two-dimensional Ginzburg-Landau-like phenomenological theory of the phenomenon is developed.
Soft Condensed Matter (cond-mat.soft)
Strontium Titanate Capping Layers as Kinetic Regulators of Redox Phase Transitions in Oxide Heterostructures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Pooya Abdollahi, Woo Jin Kim, Keaghan Knight, Harold Y. Hwang, Ambrose Seo
Oxide capping layers are widely used to protect and stabilize thin-film heterostructures, yet their role in governing phase-transition kinetics remains largely unexplored. Here, we uncover the kinetic function of few-nanometer-thick SrTiO$ _3$ (STO) capping layers in controlling oxidation and reduction processes, using real-time in situ optical spectroscopic ellipsometry. We show that oxygen diffusion through the nanoscale capping layer constitutes the rate-limiting step, giving rise to diffusion-controlled phase transitions in the underlying materials. As a result, both capping-layer thickness and oxygen partial pressure provide effective handles to tune phase transition temperatures. Quantitative analysis yields an activation energy of $ E_A$ = 0.64 $ \pm$ 0.06 eV for oxygen diffusion through STO, highlighting its suitability for precise control of redox reactions in diverse material systems. These results establish oxide capping layers as active kinetic regulators of redox-driven phase transitions and offer a general framework for engineering redox dynamics in complex oxide heterostructures.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Other Condensed Matter (cond-mat.other), Strongly Correlated Electrons (cond-mat.str-el), Chemical Physics (physics.chem-ph)
10 pages, 4 figures
Heat current and noise in a point-like junction between normal metal and fractional quantum hall edge state with $ν= 1/3$
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Redouane Zamoum, Houssam Eddine Farhi, Abdellah Touati, Adeline Crépieux
In this study, we investigate heat current correlations between two edge states coupled through a constriction in the fractional quantum Hall regime at filling factor $ \nu = 1/3$ . This configuration allows us to map the system onto an interacting Tomonaga-Luttinger liquid with a local impurity, where the interaction parameter takes the value $ \kappa = 1/2$ . This specific parameter value enables the application of the refermionization method. By solving the refermionized Hamiltonian, we compute the heat current and evaluate the finite-frequency heat auto- and cross-correlation functions. Our results reveal asymmetric behavior with frequency, corresponding to absorption and emission noise, respectively. Furthermore, we examine several limiting cases, including low- and high-temperature limits as well as strong- and weak-backscattering regimes. In the weak backscattering regime, the Lorenz number approaches $ 4L_0$ at high voltage, suggesting a rescaling of the Wiedemann-Franz law due to interactions. A detailed study of the heat current fluctuations has made it possible to identify and derive expressions for the dominant contribution in the various regimes of interest, and to reveal the predominance of partition noise.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Visualization of Single Spin-chain Propagation using Bragg Coherent Diffraction Imaging
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Xiaoqian M. Chen, Justin S. Woods, Ulrich Welp, Wai-kwong Kwok, Ralu Divan, David A. Czaplewski, Scott Dhuey, Sujoy Roy, Rajesh V. Chopdekar, Lance E. De Long, Andi Barbour, Claudio Mazzoli, Ian Robinson, J. Todd Hastings
Domain wall dynamics and their manipulation in finite-size systems serve as a promising platform for beyond Moore’s law applications. Yet, the imaging techniques to track their motion in real-space and time are limited. Here, we use magnetic domain walls formed in permalloy artificial square lattice to demonstrate that single-shot Bragg coherent diffraction imaging (BCDI) is a powerful approach for this purpose. Our BCDI reconstructed images revealed milliseconds time-scale dynamics of the antiphase magnetic domain walls traveling through an antiferromagnetically ordered sample.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Sub-monolayer tracking of molecular states at buried interfaces
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Harlan Heilman, Em Biegler, Sushil Adhikari, Victor Murcia, Tanner Melody, Fred Woodall, Lars Thomsen, Obaid Alqahtani, Brian A. Collins
Phenomena responsible for emerging technologies originate from novel molecular states at buried interfaces. Yet quantitatively resolving these features is out of reach in most cases. Resonant scattering has demonstrated sensitivity to these local states but is limited due to a lack of accurate interpretive models. We leverage a machine learning (ML)-optimized optical model to analyze polarized resonant soft X-ray scattering (RSoXS) from molecular thin films. This new analysis establishes the direct and quantitative interpretation of molecular orientation, chemical identity and packing states as a function of depth with sub-monolayer resolution - reaching beyond the diffraction limit via locking energy and polarization through the optical model. From our analysis, we discover a gradient evolution of molecular orientation and packing emerging from the interface, indicative of competing surface versus bulk growth dynamics and contradicting hypotheses of substrate patterning. This nondestructive insight into buried interfacial formation and final state opens possibilities in controlling interfacial states and phenomena in next-generation technologies.
Materials Science (cond-mat.mtrl-sci), Soft Condensed Matter (cond-mat.soft), Data Analysis, Statistics and Probability (physics.data-an), Optics (physics.optics)
Poly(vinylidene fluoride) under finite electric displacement fields: a removable $α!\to!δ$ reorientation barrier and a persistent first-order $δ!\to!β$ conformational change
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Shaohui Qiu, Jacob C. Dean, Rajagopalan Thiruvengadathan, Ramanujam Brahmadesam Thoopul Srinivasa Raghava
The $ \alpha$ , $ \delta$ , and $ \beta$ phases of PVDF are interconverted by electrical poling and mechanical drawing, yet the thermodynamics under a controlled electrical boundary condition has not been established from first principles. We evaluate the zero-temperature free energy at fixed electric displacement $ D$ from van der Waals density-functional calculations along two constrained coordinates in a common 24-atom cell: a tilt of the gauche C–C bonds that maps antipolar $ \alpha$ onto polar $ \delta$ (cell change $ <1%$ ), and a backbone torsion that straightens TG$ ^+$ TG$ ^-$ chains into all-trans $ \beta$ (chain-repeat strain $ 10.6%$ ). As $ D$ increases from 0 to $ 0.30$ ~C,m$ ^{-2}$ , the lowest homogeneous free energy switches from $ \alpha$ to $ \delta$ at $ D_{c1}=0.046$ ~C,m$ ^{-2}$ and from $ \delta$ to $ \beta$ at $ D_{c2}=0.157$ ~C,m$ ^{-2}$ . At $ T=0$ with domain-wall energy neglected, a $ \delta$ multidomain state lies $ 14.3$ ~meV per cell below homogeneous $ \alpha$ at every $ D$ . A $ \Gamma$ -point harmonic estimate suggests that vibrations reverse this ordering at room temperature. $ \delta$ and $ \beta$ coexist for $ 0.11<D<0.21$ ~C,m$ ^{-2}$ at $ E^\ast=0.69$ ~GV,m$ ^{-1}$ , independent of the screening constant. The tilt barrier falls from $ 0.66$ ~eV per cell at $ D=0$ to $ 17$ ~meV at $ D=0.30$ ~C,m$ ^{-2}$ (below $ k_BT$ at $ 300$ ~K), while the torsion barrier remains $ 0.66$ ~eV at $ D_{c2}$ and $ 0.34$ ~eV at $ D=0.30$ ~C,m$ ^{-2}$ , so $ \delta\to\beta$ stays first order. Much of the difference traces to the path effective charge ($ 0.28e$ for the tilt, $ 0.18e$ for the torsion). Scaling shows the tilt barrier would survive with the torsion charge; the smaller torsion charge accounts for about half the barrier it retains. The landscape accounts for why a field produces $ \delta$ and why $ \beta$ is reached by drawing, and suggests that raising that charge could let a field alone produce $ \beta$ .
Materials Science (cond-mat.mtrl-sci)
42 pages, 7 figures
Structural characterization of the rutile-GeO2/TiO2 (001) heterointerface
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Imteaz Rahaman, Martha R. McCartney, David J. Smith, Kai Fu
Rutile-GeO2 (r-GeO2) has emerged as a promising ultrawide-bandgap (UWBG) semiconductor for future high-power device applications because of its favorable combination of physical and electrical properties. This study has used high-resolution transmission electron microscopy (HR-TEM) to compare heterointerfaces between thin films of GeO2 grown by metal-organic chemical vapor deposition on closely-lattice-matched rutile TiO2 (r-TiO2) substrates at temperatures of 840° C and 925° C. Cross-sectional TEM observations reveal interfaces with two entirely different structures: an amorphous GeOx/r-TiO2 heterostructure with an abrupt, highly faceted and non-planar interface, or a fully epitaxial r-GeO2/r-TiO2 heterostructure characterized by a more wavy but often facetted interface. Structural analysis of the latter sample revealed a high density of strain-relieving interfacial dislocations, identified primarily as Lomer-type or 60°-type, that accommodated the ~4% lattice mismatch between the two materials, while chemical analysis showed very limited interfacial intermixing. Crystallographic analysis showed that the interface faceting was associated with rutile {101} facets, with characteristic facet angles of ~114°; these observations support thermally driven TiO2 (001) substrate faceting rather than an interface reconstruction resulting from GeO2 epitaxy. Overall, these findings provide useful insights into the mechanisms governing interface formation and strain relaxation in r-GeO2/r-TiO2 heterostructures and suggest that further refinement of growth conditions should enable improved epitaxial growth of r-GeO2 for future ultrawide-bandgap electronic device applications.
Materials Science (cond-mat.mtrl-sci)
19 pages, 5 figures
Dipole chains of Bloch point singularities revealed by X-ray magnetic tomography
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Jeffrey Neethirajan, Rikako Yamamoto, Marisel Di Pietro Martínez, Luke A. Turnbull, Praveen Vir, Chandra Shekar, Claudia Felser, Luis Carlos Colocho Hurtarte, Benedikt J. Daurer, Majid Kazemian, Burkhard Kaulich, Claire Donnelly
Bloch point singularities play an important role in magnetic systems, mediating changes in topology in three dimensional configurations. However, until now they have only been observed as isolated objects or as part of individual topological textures. Here we present the experimental observation of a 1D dipole chain of Bloch points in an anisotropic chiral magnet using soft X-ray magnetic vector tomography. We identify that the chain of Bloch point singularities lies along a boundary between regions of opposite chirality and that neighbouring Bloch and anti-Bloch points are stable at separations down to 60 nm. The stability of the Bloch points is determined to be closely related to the surrounding topology of the magnetisation configuration and a threshold separation for the spontaneous annihilation of Bloch point-anti-Bloch point pairs within chiral domain walls is identified to be approximately 90 nm in distance. This observation of a chain of Bloch points and the insight into their stability, offers a route to explore the correlative behaviour of such topological point defects. The behaviour and control of such point defects is of relevance for the control of 3D magnetisation configurations, and provides a new route towards the creation of correlated configurations of singularities in a magnetic system.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Nanoscale origin of thermal anisotropy in monoclinic \texorpdfstring{$β$-Ga$_2$O$_3$}{beta-Ga2O3}
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Kai Xu, Shuo Zhao, Luca Sung-Min Choi, Nils Bernhardt, Pouria Emtenani, Felix Nippert, Moritz Meißner, Hans Tornatzky, Oliver Bierwagen, Piero Mazzolini, Riccardo Mincigrucci, Laura Foglia, Danny Fainozzi, Filippo Bencivenga, Zbigniew Galazka, George Fytas, Bartlomiej Graczykowski, Riccardo Rurali, Matthias Scheffler, Christian Carbogno, Juan Sebastian Reparaz, Markus R. Wagner
Monoclinic $ \beta$ -Ga$ _2$ O$ _3$ is a promising ultra-wide-bandgap semiconductor for power electronics, but its low and anisotropic thermal conductivity limits heat removal, making it a compelling model system for nanoscale thermal transport studies. Here, we demonstrate a pronounced nanoscale enhancement of thermal anisotropy and uncover the underlying phonon mechanism by combining complementary thermal and acoustic spectroscopy techniques with first-principles calculations. Anisotropic thermoreflectance thermometry determines the full thermal-conductivity tensor from angular measurements within the (100), (010), and (001) crystallographic planes. Angle-resolved Brillouin light scattering reveals that low-frequency acoustic phonons exhibit only weak velocity anisotropy, insufficient to account for the measured thermal anisotropy. Frequency-resolved ab initio Green–Kubo calculations show that the bulk anisotropy pattern emerges only when the accumulated conductivity includes phonon modes above 4 THz, whereas the sub 3 THz acoustic contributions are nearly isotropic. Extreme-ultraviolet transient thermal grating spectroscopy reveals that reducing the grating period to 28 nm strongly enhances the in-plane thermal anisotropy, most markedly in the (001) plane, where it reaches nearly twice its macroscopic value. Reconstructed and calculated mean-free-path (MFP) accumulation functions link this enhancement to the stronger directional contrast of short-MFP phonons. Together, these results identify high-frequency, short-MFP phonons as the dominant origin of thermal anisotropy in $ \beta$ -Ga$ _2$ O$ _3$ , while low-frequency phonons attenuate the directional contrast at macroscopic scales.
Materials Science (cond-mat.mtrl-sci)
Spatiotemporally-resolved differential dynamic microscopy reveals strain-induced deformations in heterogeneous soft materials
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-10-26 20:00 EDT
Aysan Razzaghi, Mehrzad Sasanpour, Jasmine Ren, Caidric Gupit, Matthew E. Helgeson, Megan T. Valentine, Rae M. Robertson-Anderson, Ryan McGorty
Understanding the microscopic behavior of materials in response to mechanical perturbations is a central challenge in soft matter, yet existing methods, which typically rely on microscopy-based imaging, often struggle with spatial heterogeneity and low signal-to-noise that are characteristic of many soft and biological materials. Additionally, many existing rheo-optical methods focus on the response to macro-scale forces rather than localized perturbations despite the importance of local stresses in biological and industrial applications of soft materials. Here, we present STroboscopically Averaged, time-Resolved Differential Dynamic Microscopy (starDDM) to investigate a sample’s deformation across time and distance due to a cyclically applied local force. As proof-of-principle, we use this model-independent and tracer-free approach to map the motions of active cytoskeleton composites imposed by the movement of an optically trapped probe particle embedded within the complex network. We reveal how motor-driven restructuring and varying strain rates tune the magnitude and propagation of the response, which we further show decays with distance from the perturbation. This analytical platform fills a critical gap in micro-rheology, offering a versatile tool for probing the non-equilibrium dynamics of soft materials ranging from biopolymer networks to 3D-printed materials and soft robotics.
Soft Condensed Matter (cond-mat.soft)
Boundary shape controls the stress distribution in two-component elastic materials
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2026-10-26 20:00 EDT
Kyungeun Kim, Adam Clare, Miranda Holmes-Cerfon
We investigate how the shape and arrangement of high-stiffness regions govern stress redistribution in two-component triangular elastic spring networks subjected to spatially correlated and uncorrelated random prestress. We compare boundary roughness, partitioning into disconnected regions, and graded transitions between regions of different stiffness. Our simulations identify interface bonds as channels for energy transfer: increasing their number provides additional transfer paths and reduces stress concentration in mechanically rigid regimes, while offering little benefit in compliant subnetworks. This is analogous to defects in naturally occurring crystal structures, where the defects themselves isolate stress. At a fixed fraction of high-stiffness material, partitioning reduces stress concentration for both correlated and uncorrelated prestress. The benefit diminishes with further subdivision as the number of interface bonds becomes comparable to the number of interior nodes. Stress reduction, however, depends on the spatial correlations of the imposed prestress: random prestress generally yields a stronger effect, though the difference diminishes in some regimes. Graded interfaces further reduce peak stress by distributing the stiffness transition over a broader region. Together, these results suggest design strategies based on increasing interface area, matching subdivision scale to prestress correlations, and grading stiffness transitions. This minimal framework identifies how internal structure controls energy transfer and stress redistribution, suggesting design principles for mechanical robustness under both internal and external loading.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Materials Science (cond-mat.mtrl-sci), Soft Condensed Matter (cond-mat.soft)
14 pages, 15 figures
The Extended Diode Equation
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Jianhong Yang, Gonghao Sun, Tinglan Li
For more than 75 years, the p-n junction current-voltage characteristic has been derived by treating majority carriers as an inert background and conflating the junction voltage with the applied bias. Here we show that the base electric field, generated by the coupling of excess majority and minority carriers, fundamentally alters the internal potential distribution. This self-consistent framework yields a closed-form extended diode equation that reproduces the high-injection roll-off without invoking an external series resistance, thereby eliminating an empirical patch that has persisted in the classical theory.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
Heterogeneous superconductivity emerging from a charge-stripe state in kagome lattices
New Submission | Superconductivity (cond-mat.supr-con) | 2026-10-26 20:00 EDT
Hongyu Li, Shuikang Yu, Huachen Rao, Zhuying Wang, Xingchen Zhou, Houpu Li, Yunmei Zhang, Zhao Gong, Xin Yu, Rui Wu, Tao Wu, Zhenyu Wang, Ziji Xiang, Xianhui Chen
Charge density wave (CDW) and superconductivity have long been recognized as competing orders. However, recent achievements establish that the interplay between these two collective electronic phenomena can be more perplexing, with emergent phenomena arising from their cooperation. Here we report a distinctive case of the kagome superconductors CsV3Sb5-xSnx, in which the characteristics of superconductivity evolve in accordance with the form of CDW order. As the triple-Q CDW in CsV3Sb5 transforms to a short-range stripelike CDW at xc = 0.07, a sudden change in superconducting properties occurs concomitantly. A combination of thermodynamic, electrical transport and scanning tunneling microscopy experiments reveals a heterogeneous superconducting state beyond xc: the superconducting gap exhibits pronounced spatial variation, in conformity with a distribution of critical temperature and the resulted superconducting precursor effects. Moreover, abundant normal fluid persists deep into the superconducting state, as evidenced by remnants of electronic specific heat and zero-energy quasiparticle interference. These observations are unrelated to the chemical inhomogeneity and residual strain effect introduced by Sn substitution. Instead, they emulate the phenomenology that a sign-changing superconducting order parameter is subject to strong pair-breaking scattering with the short-range charge stripes and hence reflect the unconventional nature of superconductivity developing inside the charge-stripe state.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Accepted by Nature Communications
A Self-Consistent Two-Carrier Drift-Diffusion Framework for p-n Junctions: Extended Diode Equation, Power Dissipation, and Base Transit Time
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Jianhong Yang, Tinglan Li, Gonghao Sun
The classical theory of p-n junctions derives the current-voltage characteristic from minority-carrier diffusion alone: majority carriers are treated as an inert background, the quasi-neutral base as field-free, and the junction voltage as equal to the applied bias. These premises fail together under high bias and high-level injection, where the observed current roll-off is reproduced only by appending an empirical series resistance outside the junction physics. Here we develop a self-consistent two-carrier drift-diffusion framework that introduces no assumption beyond the classical ones. Excess majority carriers are shown to be electrostatically forced transport participants: the ambipolar diffusion equation, closed by exact two-sided boundary conditions, yields a unified excess-carrier profile. The resulting base field separates into an ohmic and a Dember component, and all four current components follow in closed form, their sum being position independent. At device level the framework closes into an extended diode equation that contains the Shockley equation as its low-injection, long-base limit and reproduces the n=2 roll-off intrinsically. The junction voltage emerges as a self-limiting drop confined to the space-charge region and separated from the applied bias by exact base drops. Two device-level corrections are quantified: at high current, 75-90% of the dissipation migrates from the junction into the quasi-neutral base, and field-assisted acceleration shortens the base transit time by up to a factor of six. Three parameter-free predictions follow: a universal ideality-factor crossover that passes through 3/2 when the boundary excess equals the doping, a high-injection onset voltage that scales as 119 mV per decade of doping, and a geometry factor that survives into high injection.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
Material criteria for angular-momentum transfer from twisted photons to photoelectrons
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
A. A. Shchepkin, D. V. Karlovets
We study the material requirements for transferring the total-angular-momentum (TAM) projection of a twisted photon to the orbital angular momentum (OAM) of a photoelectron emitted from an $ n$ -type semiconductor surface. Within a single-valley effective-mass model of surface photoemission, we calculate OAM-resolved spectra for GaAs, InSb, $ \mathrm{InAs}{0.34}\mathrm{Sb}{0.66}$ , and $ \mathrm{Hg}{0.76}\mathrm{Cd}{0.24}\mathrm{Te}$ irradiated by twisted photons with Laguerre–Gaussian–like momentum profile. The OAM transfer is characterized by the mean electron OAM, its root-mean-squared width, and the fraction of electrons with OAM-projection equal to the photon TAM-projection. Efficient transfer requires the transverse momentum of the conduction electron to be much smaller than the transverse momentum width of the photon, which favors low temperatures, small conduction-band effective masses, and shallow donor levels. GaAs is less favorable within the present model because of its larger effective mass and deeper donor levels. We also discuss the demanding photon-wave packet parameters, possible extensions to Dirac and Weyl semimetals, and post-emission OAM selection. Although the generation of vortex electrons with a vanishing OAM uncertainty via photoemission seems challenging, we argue that it is still possible to generate single-electron vortex states with a finite OAM dispersion.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Quantum Physics (quant-ph)
15 pages, 3 figures
Kinetic competition controls loss-induced exceptional points of Hubbard pairs
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-10-26 20:00 EDT
Two-body loss can bind two fermions in a Hubbard lattice, yet the binding threshold in the infinite lattice need not be an exceptional point (EP). At fixed total momentum $ \mathbf{K}$ , the hops of the two particles interfere into a relative-motion hopping along each lattice direction, which sets the kinetic energy of the relative motion. On a hypercubic lattice, the threshold $ g_c=1/[\pi\rho_2(0)]$ is an EP precisely when the maximum kinetic energy along one direction exceeds the sum of the transverse maxima. This dominance keeps every transverse-momentum scattering channel propagating near the band center, making the local pair Green function purely imaginary there. Two real-energy scattering zeros associated with coherent perfect absorption then coalesce at the threshold into a second-order EP of the analytically continued pair problem, where loss restores the parity-time symmetry of the pair’s scattering solutions. Without a dominant direction, binding occurs without coalescence and without breaking of that symmetry. Total momentum can therefore select EP sectors even on isotropic lattices. More broadly, the kinetic structure of the two-particle continuum determines whether loss-induced binding and exceptional degeneracy coincide.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
6 pages, 4 figures; Supplemental Material: 27 pages, 4 figures
Zeeman Shift and Injection Currents under Light Irradiation
New Submission | Other Condensed Matter (cond-mat.other) | 2026-10-26 20:00 EDT
Ruizhi Dong, Yihua Xiao, Pengfei Wang, Ruixiang Fei
The conversion of light into electrical currents enables energy harvesting and photodetection. Conventional second-order dc photocurrents are driven by the electric component of light through electric-dipole coupling and require broken inversion symmetry. Here, we show that the electric and magnetic components of light jointly generate Zeeman shift and injection currents. Using quantum perturbation theory, we derive explicit microscopic expressions for their conductivity tensors. We systematically classify the symmetry constraints on these responses and show how they differ from those governing conventional photocurrents. In particular, both responses can occur in centrosymmetric systems with spin-orbit coupling or noncollinear magnetic order, irrespective of time-reversal symmetry. A centrosymmetric kagome model exhibits broadband responses. First-principles calculations for Mn$ _3$ Sn further predict Zeeman injection and shift current densities of $ 10^{2}$ -$ 10^{3}\mathrm{A/m^{2}}$ and $ 1$ -$ 10\mathrm{A/m^{2}}$ , respectively, under illumination with an electric-field amplitude $ E=10^{4}~\mathrm{V/m}$ . These magnitudes place both currents within experimental reach.
Other Condensed Matter (cond-mat.other)
Compass Correlations in a Square-Lattice Magnet
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-10-26 20:00 EDT
Otkur Omar, Matthias D. Frontzek, Gabriele Sala, Junying Shen, Xinmin Wang, Ze Hu, Zhuang Xu, Zecong Qin, Xin Tong, Joe Paddison, Max Hirschberger, Shinichiro Seki, Masaaki Matsuda, Matthew B. Stone, Andrew D. Christianson, Nguyen D. Khanh, Shang Gao
The square-lattice compass model is a paradigm of bond-dependent frustration, yet experimental evidence for its characteristic spin correlations has remained elusive. Here we identify compass correlations in the square-lattice intermetallic ErRu$ _2$ Si$ _2$ using single-crystal neutron diffuse scattering. Comparative measurements on the isostructural compounds NdRu$ _2$ Si$ _2$ and ErRu$ _2$ Si$ _2$ reveal a pronounced contrast between nearly uniform diffuse rings in the former and strong intensity modulation between Brillouin zones in the latter. Through the magnetic neutron polarization factor, this modulation reveals compass correlations that couple moment orientation to the correlation wavevector. Crystal-field spectroscopy identifies four preferred in-plane orientations for the Er$ ^{3+}$ moments. A minimal compass-Heisenberg model incorporating this anisotropy quantitatively reproduces the diffuse scattering and accounts for the double-$ Q$ vortex-antivortex ground state. Fits with the compass couplings fixed at values set by the dipolar energy scale retain good agreement with the data, supporting a substantial dipolar contribution to the bond-dependent interactions. Our results establish a square-lattice platform for compass physics and suggest that dipolar interactions, acting together with local crystal-field anisotropy, can shape directional magnetic correlations alongside conduction-electron-mediated exchange.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
8 pages, 4 figures
Magnonic time crystal with lasing coherence
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Jiantao Song, C. K. Wei, Shuhuan Ma, Yiming Pan, Zhijian Chen, Li Yu, Wei Lu, Bimu Yao
Discrete time crystals (DTC) can respond at an integer multiple of the drive period. Internal order-parameter measurements have advanced studies of this novel non-equilibrium phase of matter; however, turning this order into highly coherent, externally accessible radiation remains challenging: pump-driven nonlinear processes must supply sufficient gain to compensate dissipation while preserving subharmonic stability. Here we realize a room-temperature magnonic time crystal (MTC) with radiation of lasing coherence using a pump-induced magnon mode in yttrium iron garnet. A microwave beat drive produces robust period doubling over a finite parameter range, with spectral signatures of higher-order MTC at stronger driving. The emitted field exhibits linewidth narrowing to 260.0 Hz and a first-order correlation decay time of $ 995 \mu s$ . Our model links this response to three-magnon confluence, yields a stability region consistent with experiment and predicts a possible transition to chaos. We further map the complex temporal dynamics into frequency-resolved nonlinear features for reservoir computing. These results bridge time-crystalline order and nonlinear information processing through intrinsic magnon-magnon interactions and lasing coherence.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
10 pages, 5 figures,
Intrinsic Paramagnetism of Optical Phonons and Thermal Hall Effect in Quantum Paraelectrics
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-10-26 20:00 EDT
Harsh Jain, Manideep Gone, Nabyendu Das
We propose a microscopic theory of the phonon-mediated thermal Hall effect in quantum paraelectrics, driven by the intrinsic paramagnetism due to quantum fluctuations of the (nearly) critical optical phonon modes. The effective magnetization due to temporal fluctuations of the assosciated dipoles couple to an external magnetic field resulting the magnetoelectric term $ \mathbf{H} \cdot (\mathbf{P} \times \dot{\mathbf{P}})$ in the effective Lagrangian density of the polarisation field $ \mathbf{P}$ . This coupling splits the transverse optical phonon spectrum into right- and left-circularly polarized chiral branches. Using the chiral phonon Green’s functions and the Kubo formalism, we derive the thermal Hall conductivity $ \kappa_{xy}$ from the heat-current correlation function. We observe that $ \kappa_{xy}$ is proportional to the difference in spectral weights of the two chiral modes, $ \kappa_{xy} \propto A_+^2 - A_-^2$ , establishing a direct microscopic link between phonon chirality and transverse heat transport. Our theory predicts three key observations: (i) a linear-in-magnetic-field response $ \kappa_{xy} \propto H$ at low fields, evolving into nonlinear behavior at higher fields (ii) a non-monotonic temperature dependence of $ \kappa_{xy}$ with a peak arising from the competition between thermal population and phonon scattering and (iii) strong enhancement of $ \kappa_{xy}$ near the quantum critical point $ \omega_0 \to 0$ , it exhibits power-law scaling $ \kappa_{xy} \propto T^{\alpha}$ with $ \alpha \approx 0.41$ . Our findings provide an understanding of thermal Hall transport in quantum paraelectrics due to intrinsic paramagnetism and is aligned with the observed behaviour in SrTiO$ _3$ and related materials.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Interface Control of Second-Harmonic Generation in Layered CuInP2S6 via PbZr0.2Ti0.8O3 Domain Wall
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Dawei Li, Juhe Liu, Yifei Hao, Qiuchen Wu, Xi Huang, Jesse Stebbing, Xinyi Hou, Gaolei Zhao, Kun Wang, Yongfeng Lu, Xia Hong
The control of nonlinear optical responses in van der Waals ferroelectrics at the nanoscale offers opportunities for developing two-dimensional integrated nanophotonics with programmable functionalities. In this work, we report the first realization of nanoscale nonvolatile control of the amplitude and polarization of second-harmonic generation (SHG) response in layered CuInP2S6 (CIPS) via the domain structure in an interfacial PbZr0.2Ti0.8O3 (PZT) thin film. The SHG intensity at CIPS/PZT heterointerface is continuously modulated, either substantially enhanced or almost entirely quenched, by the circular domain walls in underlying ferroelectric oxide. The interfacial coupling of CIPS polar axis with in-plane polarization of PZT domain walls tailors the SHG light polarization into two-fold (C2V) symmetry, which is well modeled by nonlinear electromagnetic theory. Overall, this study enables nonvolatile programmable design of nonlinear light intensity and polarization in van der Waals ferroelectrics at the nanoscale.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
18 pages, 4 figures
Bose-Einstein condensate in a shell: nonlinear modes and symmetry breaking
New Submission | Quantum Gases (cond-mat.quant-gas) | 2026-10-26 20:00 EDT
Alexander Wolf, Vladimir V. Konotop, Maxim A. Efremov
The state of a quantum particle confined to a spherical surface is commonly described using spherical harmonics, which play a crucial role in solving many scientific problems featuring spherical symmetry. A mean-field description of a system of many interacting quantum particles confined to a spherical shell naturally leads to nonlinear generalizations of spherical harmonics. In this study, we analyze the emergence of such nonlinear modes in a shell-shaped Bose-Einstein condensate with both repulsive and attractive two-particle interactions. We find several classes of nonlinear modes. The first kind is an analytical continuation of a single spherical harmonic or their superposition for nonvanishing atom-atom interaction. Some of these solutions have planar counterparts in the form of Townes solitons and Townes vortices, which either appear stable even in the case of attractive interactions or can be stabilized by three-particle interactions. The second kind originate from symmetry-breaking bifurcations in the case of a repulsive interaction, and therefore have no linear counterparts. Moreover, we demonstrate the existence of a breathing dynamics that oscillates primarily between an unstable soliton and a stable vortex necklace state. Our findings show that the physics of nonlinear matter waves on curved geometries differs substantially from that in planar systems, suggesting the feasibility of observing these unconventional wave patterns experimentally.
Quantum Gases (cond-mat.quant-gas), Pattern Formation and Solitons (nlin.PS), Quantum Physics (quant-ph)
Measurement speed limit and Cramér-Rao bound for time-averaged estimators
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-10-26 20:00 EDT
Hiroyuki Odajima, Andreas Dechant
We consider a measured system $ X$ containing a parameter $ \theta$ of interest and the problem of estimating this parameter by observing a second, coupled measurement system $ Y$ . We show that, in thermodynamic equilibrium, the Fisher information of $ Y$ associated with the parameter is bounded by that of $ X$ , implying that conservative interactions between $ X$ and $ Y$ reduce the precision of parameter estimation. Conversely, out of equilibrium, we show that the Fisher information of $ Y$ can exceed that of $ X$ , so that non-conservative interactions can potentially increase the precision of parameter estimation. For idealized, back-action-free measurements, where the coupling to $ Y$ does not perturb $ X$ , we derive a speed limit for the increase of Fisher information of $ Y$ . This speed limit only depends on the properties of the measured system $ X$ and places a fundamental bound on the precision of any back-action-free measurement. As a corollary, we obtain a generalized Cramér-Rao bound (CRB) for time-averaged estimators. We illustrate our results for linear dynamics and suggest a scheme for disturbance-free non-equilibrium sensing with improved accuracy.
Statistical Mechanics (cond-mat.stat-mech)
17 pages, 6 figures
Intrinsic Raman Modes and Crystal Symmetry of Altermagnetic $α$-MnTe
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Yunpeng Cui, Shuai Zhang, Jia-Liang Xie, Jinxuan Liang, Hao Lin, Miao Qin, Jiawei Shao, Gongling Chen, Yidian Li, Yixuan Luo, Deng Hu, Bingru Lu, Hao Li, Xiang Li, Tiantian Liu, Haodong Yu, Hongyun Zhang, Shuyun Zhou, Zhiwei Wang, Yanfeng Guo, Tiantian Zhang, Miao-Ling Lin, Ping-Heng Tan, Feng Jin, Luyi Yang
Crystal symmetry governs the physical properties of materials and provides the framework for interpreting their microscopic excitations and macroscopic responses. In altermagnets, the crystal symmetries that relate opposite-spin sublattices give rise to momentum-dependent spin splitting despite compensated magnetization. Determining the real crystal symmetry is therefore essential for understanding the intrinsic electronic and magnetic properties. For the altermagnetic semiconductor $ {\alpha}$ -MnTe, conflicting Raman assignments have left both its intrinsic lattice excitations and its crystal symmetry unresolved. Here we combine high-resolution Raman and second-harmonic generation (SHG) spectroscopy with first-principles calculations to distinguish intrinsic lattice excitations from Te-derived spectral contributions and to examine bulk inversion symmetry of $ {\alpha}$ -MnTe. We show that several prominent Raman features previously assigned to $ {\alpha}$ -MnTe instead originate from segregated Te clusters or precipitates. The remaining intrinsic Raman response consists of a single Raman-active mode assigned to the calculated $ E_{2g}$ phonon, consistent with the centrosymmetric $ D_{6h}$ symmetry. The SHG response agrees with surface electric-dipole and bulk electric-quadrupole contributions expected for a centrosymmetric $ D_{6h}$ crystal, supporting the preservation of bulk inversion symmetry in $ {\alpha}$ -MnTe. Our findings revise the Raman assignments in $ {\alpha}$ -MnTe and provide a basis for interpreting its altermagnetic properties within the appropriate crystal-symmetry framework.
Materials Science (cond-mat.mtrl-sci)
Nonlocal Thermoelectric Transport in Degenerate Electron Systems
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Albert Beardo, Adrián Ramos-Martín, Jordi Tur-Prats, F. Xavier Alvarez, Juan Camacho
When the characteristic length scales of transport become comparable to the carrier mean free path, the local constitutive description breaks down. We develop the Flux Derivative Formalism (FDF), a kinetic framework that provides a systematic route from the Boltzmann equation to nonlocal constitutive equations. We use it to derive coupled equations for charge and heat transport in isotropic electronic systems, together with boundary conditions derived consistently within this approach, yielding a closed macroscopic description that can be applied to complex geometries without solving the full Boltzmann problem. The explicit transport coefficients are derived for degenerate electronic systems within the Callaway model. A central result is that varying the relative strength of resistive and momentum-conserving collisions changes the transport coefficients but not the non-local constitutive structure, providing a continuous description from resistive-dominated transport to the collective hydrodynamic limit. The electronic heat equation takes a Guyer-Krumhansl form, whose predictions are validated against size-dependent thermal-transport measurements in Cu and Ni. For coupled thermoelectric transport, the resulting boundary-value problem determines the complete geometry-dependent transport matrix. Comparison with spatially resolved Boltzmann solutions confirms quantitative accuracy down to transverse dimensions comparable to the carrier mean free path. The theory predicts geometry-dependent Seebeck and Peltier coefficients while preserving Onsager reciprocity and the Kelvin relation.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
29 pages, 7 figures
Triplon dynamics from partial Kondo screening in frustrated heavy-fermion systems
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-10-26 20:00 EDT
Hiroki Nakahara, Masahito Mochizuki, Rintaro Eto
The partially disordered (PD) phase, in which magnetically ordered and Kondo-screened sites coexist, has been proposed as a possible ground state of geometrically frustrated heavy-fermion systems. We investigate its dynamical properties in the half-filled periodic Anderson model on a triangular lattice by calculating the dynamical spin susceptibility within the random-phase approximation built on a self-consistent Hartree-Fock solution. We show that successive quantum phase transitions from the Kondo-insulating phase to the PD phase and to a magnetically ordered phase are driven by the condensation of triplon modes originating predominantly from the Kondo-screened sites. In the PD phase, magnons and triplons coexist and hybridize, leading to characteristic level repulsion in the excitation spectrum. These results reveal how triplet excitations evolve into collective magnetic modes across the successive phase transitions and highlight the dynamical interplay between magnetic order and Kondo screening in frustrated heavy-fermion systems.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
9 pages, 4 figures
Existence and Absence of Spin-Glass Phases on Migdal–Kadanoff Hierarchical Lattices: A Complete Classification
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2026-10-26 20:00 EDT
Manaka Okuyama, Masayuki Ohzeki
We consider the Ising spin-glass model on Migdal–Kadanoff (MK) hierarchical lattices, characterized by the fractal dimension $ d=1+\log s/\log b$ , where $ s$ and $ b$ denote the number of parallel branches and the number of bonds in series within each branch, respectively. For independent Gaussian couplings, we rigorously establish a necessary and sufficient condition for the existence of finite-temperature spin-glass order for arbitrary integers $ b,s\ge2$ . We prove that a finite-temperature spin-glass phase exists whenever [ \frac{b}{\sqrt{s}} \left( \frac{b\sqrt{s(s-1)}}{bs-1} \right)^{s-1}<1. ] In particular, this condition holds for all three-dimensional MK hierarchical lattices ($ d=3$ , or equivalently $ s=b^2$ ), regardless of the choice of $ b$ . Conversely, we prove the absence of finite-temperature spin-glass order for fractal dimensions $ d<1+\log17/\log6\approx2.58$ , as well as in the large-$ b$ limit for any fixed $ d<3$ . In the intermediate regime $ 1+\log17/\log6\le d<3$ , we provide a finite-step procedure to determine the presence or absence of spin-glass order, which depends on $ b$ and $ s$ . Our results provide a complete characterization of finite-temperature spin-glass order on MK hierarchical lattices.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Mathematical Physics (math-ph)
26 pages, 0 figure
Banded Chaos and Time-Semicrystalline Order
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-10-26 20:00 EDT
Recent work has introduced the notion of a time semicrystal, a driven nonequilibrium regime in which subharmonic temporal order survives inside deterministic chaos. Here we revisit this phenomenology from the viewpoint of classical nonlinear dynamics. Banded chaotic attractors consist of a finite number of chaotic sectors cyclically permuted by stroboscopic evolution, allowing discrete subharmonic spectral components to coexist with a broadband chaotic continuum. Exemplified through the driven Duffing oscillator and the logistic map, this structure naturally reproduces the characteristic signatures of time-semicrystalline dynamics. Within this framework, periodic subharmonic motion can enter chaos through the familiar period-doubling cascade while retaining a well-defined temporal skeleton governed by the universal Feigenbaum scaling. Temporal order within chaos can also reorganize or collapse through distinct mechanisms, producing continuous or abrupt transitions that may be intertwined with symmetry changes. These results connect time-semicrystal phenomenology with established structures of dissipative nonlinear dynamics, showing that its essential ingredients already arise in standard nonlinear systems and providing a simple framework for extending and testing the paradigm in more complex, many-body, and experimental settings.
Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Theory (hep-th)
v1: comments welcome
Flexo-Photoresponses from First Principles
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Zhichao Guo, Hua Wang, Haowei Xu
Many functionally important materials, such as silicon, possess high-symmetry crystal structures that forbid even-order nonlinear optical responses, thereby limiting their application in e.g., photonics and optoelectronics. Strain gradients can effectively break symmetries, activating otherwise forbidden optical responses. Although such flexo-photoresponses have attracted considerable interest recently, a comprehensive microscopic theoretical framework is still lacking. Here, we develop a first-principles approach that can systematically evaluate a wide range of flexo-photoresponses in realistic materials. By mapping strain gradients to long-wavelength phonons within the established theory of electron-phonon coupling, our approach captures the nonlocal quantum-mechanical effects of lattice deformations on nonlinear optical responses. Applying the framework to prototypical centrosymmetric materials, including Si, cubic $ \rm SrTiO_3$ , and monolayer black phosphorus, we demonstrate that a strain gradients of $ 10^5\sim10^6~\rm m^{-1}$ can induce flexo-second-harmonic generation and flexo-bulk photovoltaic effects comparable to the intrinsic responses of non-centrosymmetric crystals. Our work establishes a rigorous foundation for strain gradient engineering of light-matter interactions, opening new avenues for nanoscale optomechanics, optoelectronics, and beyond.
Materials Science (cond-mat.mtrl-sci)
Strain-tunable van Hove singularity and superconducting dome in monolayer kagome metal CsTi$_3$Bi$_5$
New Submission | Superconductivity (cond-mat.supr-con) | 2026-10-26 20:00 EDT
Run Lv, Wenqian Tu, Dingfu Shao, Yuping Sun, Wenjian Lu
The recently discovered titanium-based kagome metal CsTi$ _3$ Bi$ _5$ , which exhibits superconductivity without an accompanying charge density wave, provides an ideal platform to investigate the intrinsic electronic structure and superconductivity. Moreover, it enables the exploration of superconductivity in the two-dimensional limit of the kagome lattice. Here, we systematically investigate the influence of biaxial mechanical strain ($ \varepsilon$ ) on the electronic structure and superconductivity of monolayer CsTi$ _3$ Bi$ _5$ using first-principles calculations. We demonstrate that the prominent van Hove singularity (VHS) at the M point can be monotonically tuned to the Fermi level by tensile strain. Furthermore, the superconducting transition temperature $ T_C$ exhibits a dome-shaped dependence on strain, reaching a maximum of 3.6 K at an optimal tensile strain of $ \varepsilon=+2%$ . The average superconducting gap magnitude is 0.35 meV, with an orbital-dependent and anisotropic distribution. Our results provide a detailed understanding of the superconductivity of monolayer CsTi$ _3$ Bi$ _5$ and show that strain is an effective, continuous tuning knob for manipulating the electronic structure and superconductivity.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
Low-Temperature Hybrid Monte Carlo for Perylene and Corannulene: Stabilizing Determinant and Force
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-10-26 20:00 EDT
Petar Sinilkov, Thomas Luu, Johann Ostmeyer, Finn L. Temmen, Marcel Rodekamp
We demonstrate a real world physics study of the molecules perylene and corannulene at different doping levels, and calculating selected one-, two- (exciton) and three-body (trion) correlators. This has been done by performing Hubbard-model simulations near room temperature. We find, between charge neutral and doubly charged plateaus of perylene, an interaction-induced $ \Delta Q = 1$ plateau whose width grows with interaction strength and in which the ground state is a spin doublet rather than a singlet. The algorithmic advancement enabling this study simultaneously stabilizes the determinant and force calculations to machine precision at room temperature, while scaling as well as standard determinant Quantum Monte Carlo simulations of these systems. Furthermore, our formalism retains the full time-displaced (2-point) Green’s function, allowing us to construct any $ n$ -body correlator, including those that contain disconnected diagrams.
Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Lattice (hep-lat)
9 pages, 5 figures, contribution to the The 43rd International Symposium on Lattice Field Theory (LATTICE2026)
Quantum Landau Lifshitz Gilbert equation in ferromagnetic conductors and magnetic insulators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Understanding the microscopic origin of magnetic damping is essential for describing magnetization dynamics in nanoscale magnetic systems. In this work, we develop a microscopic framework to derive Gilbert damping terms from specific interactions in ferromagnetic conductors and magnetic insulators. In ferromagnetic conductors, magnetic damping is dominated by the s d exchange interaction between the localized magnetic moments and the itinerant electrons, which is effectively equivalent to an electronmagnon interaction. From the spin diffusion equation and the spin transfer torque therein, we obtain the corresponding quantum LLG equation. In magnetic insulators, where free electrons are absent, spin phonon interactions become the primary source of the this http URL from an effective spin phonon interaction and using linear response theory, we derive a quantum LLG equation with a Gilbert damping tensor analytically. Our results demonstrate that different microscopic interactions lead to qualitatively different structures of magnetic damping. Instead of being described by a universal scalar parameter, Gilbert damping can exhibit spatial dependence and tensorial characteristics determined by the underlying microscopic interactions.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
2 figures
Electron Wavefronts Capture Nanoscale Movies of Hypersound at Surfaces
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Johannes Otto, Leon Brauns, Benjamin Schroeder, Claus Ropers
Acoustic waves transport mechanical energy and elastic strain through solids, with material composition and shape governing their propagation. In the gigahertz hypersound regime, acoustic wavelengths reach tens to hundreds of nanometres, comparable to nanoscale device dimensions. Harnessing these waves underpins high-frequency signal processing, sensing, electromagnetic coupling and quantum control. Acoustic metrology probes elastic modes and internal interfaces. Yet directly imaging how nanoscale acoustic waves interact with local structure remains challenging, requiring picometre displacement sensitivity combined with high spatiotemporal resolution. Here we demonstrate full-field imaging of laser-induced hypersound at surfaces using reflected electron wavefronts. We introduce ultrafast low-energy electron microscopy (ULEEM), exploiting the intrinsic surface sensitivity of few-electronvolt electrons. Coherent electron pulses down to femtosecond durations reflect from the topmost atomic layers, imprinting the evolving surface profile onto their wavefronts. Defocus converts phase variations into image contrast. In a thin van der Waals material, we image the thermoelastic generation and propagation of picometre-amplitude acoustic waves. Measured dispersion relations, interpreted through elastodynamic modelling, distinguish substrate-supported and locally detached regions, revealing how interfacial contact shapes propagation. Delayed wave emission reveals scattering at buried mechanical defects. Our results establish electron-wavefront imaging of nanoscale surface dynamics, enabling the exploration of ultrafast energy transport, structural transformations and coupled mechanical, electronic and magnetic phenomena.
Materials Science (cond-mat.mtrl-sci), Instrumentation and Detectors (physics.ins-det), Optics (physics.optics)
22 pages including 5 pages of Supplementary Information, 5 main figures, 2 Extended Data figures, 8 supplementary videos
On the Role of Atomic Mobility in the Polyamorphism of Metallic Glasses
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Jie Shen, Antoine Cornet, Pei-Hao Sun, Valerio Di Lisio, Daniele Cangialosi, Klara Otto, Isabella Gallino, Martin Rosenthal, Eloi Pineda, Giulio Monaco, Marco Di Michiel, Yong-Hao Sun, Wei-Hua Wang, Ruta Beatrice
Understanding the microscopic mechanisms underlying polyamorphic transitions requires simultaneous knowledge of thermodynamic and structural evolution, which has remained experimentally inaccessible. Here, we combine chip-based fast differential scanning calorimetry with high-energy synchrotron X-ray diffraction to simultaneously probe the thermodynamic and structural evolution during the polyamorphic transition of a Pd-Ni-P metallic glass. Correlating heat-flow signals with the corresponding structural evolution during both heating and cooling reveals a direct relationship between thermodynamic evolution and medium-range structural ordering. Based on this relationship, we identify two distinct transition mechanisms. In the glassy state, the transition proceeds continuously through progressive medium-range ordering, accompanied by enhanced thermal stability and strongly temperature-dependent kinetics. In contrast, in the equilibrium supercooled liquid, the transition proceeds through the coexistence of distinct amorphous states, with only a weak temperature dependence of the kinetics. These findings show that atomic mobility governs the transformation pathway by coupling thermodynamic evolution to structural ordering, providing new insights into polyamorphic transitions in nonequilibrium amorphous systems.
Materials Science (cond-mat.mtrl-sci)
Electronic structure of a persistent excitonic fluid far beyond the Mott limit
New Submission | Other Condensed Matter (cond-mat.other) | 2026-10-26 20:00 EDT
Weiyan Qi, Stefano Ponzoni, Ashim Pramanik, Vitaly Gorelov, Yannis Laplace, Gianluca Stefanucci, Enrico Perfetto, Esteban Morcos, Marino Marsi, Steven Francis Udaundo, Sebastian Maherlein, Amina Taleb-Ibrahimi, Kaibo Zheng, Tonu Pullerits, Luca Perfetti
Excitons are conventionally expected to destabilize at high photoexcitation densities, as screening weakens the electron-hole attraction. Recent studies, however, challenge this paradigm, suggesting that excitons generated by strong optical pumping can remain stable even beyond the onset of population inversion. Here, using time- and angle-resolved photoelectron spectroscopy on 2D hybrid perovskites, we provide direct evidence for such a high-density excitonic state, characterized by a distinctive Mexican-hat dispersion. Remarkably, this excitonic band reconstruction endures for orders of magnitude longer than the optical coherence time, revealing a population-sustained electronic structure that survives well into the incoherent regime. The excitonic resonance also persists far beyond optical saturation, at densities where exciton wavefunctions strongly overlap. Our findings reveal a long-lived, high-density quantum fluid of excitons with characteristics reminiscent of a BCS condensate, an electronic structure markedly different from that of the dilute limit.
Other Condensed Matter (cond-mat.other)
6 pages, 4 Figures
Interplay of Chemical Disorder, Vortex Pinning, and Electron Correlations in the Mechanically Robust Medium-Entropy Alloy Superconductor $\text{Nb}{0.45}\text{Ta}{0.25}\text{Ti}{0.15}\text{Hf}{0.15}$
New Submission | Superconductivity (cond-mat.supr-con) | 2026-10-26 20:00 EDT
Pooja Chourasia, Samiul Sk, Nikita Sharma, B. Vignolle, Abhishek Sarkar, Olivier Toulemonde, Sanjoy Mahatha, S. K. Panda, Sourav Marik
Medium and high-entropy alloys have emerged as a promising class of superconducting materials because their intrinsic chemical disorder can simultaneously enhance mechanical robustness and modify superconducting properties. Here, we present a combined experimental and first-principles investigation of the structural, superconducting, electronic, and local lattice-distortion characteristics of the mechanically robust medium-entropy alloy $ \text{Nb}{0.45}\text{Ta}{0.25}\text{Ti}{0.15}\text{Hf}{0.15}$ . The material shows type-II superconductivity with a transition temperature $ T_C^{onset} \approx 7.8 \mathrm{K}$ . A high critical current density of $ J_c = 0.48 \times 10^{6}\mathrm{A/cm^2}$ is observed, and this is attributed to strong vortex pinning at grain boundaries. Specific-heat analysis indicates a strong electron-phonon coupling ($ \lambda$ = 1.07) with a large isotropic s-wave superconducting gap. Density functional theory calculations explicitly model the intrinsic chemical disorder, predict a stable body-centered cubic phase. These calculations further reveal a metallic electronic structure with substantial Ti- and Ta-derived states at the Fermi level. Additionally, our results quantify a pronounced disorder-induced local lattice distortion ($ \Delta d = 0.086$ A), providing a microscopic basis for the experimentally observed enhanced vortex-pinning landscape. Remarkably, the alloy also exhibits an unusually large Kadowaki-Woods ratio, placing it close to the heavy-fermion regime and indicating enhanced electronic correlations beyond conventional alloy superconductors. Our results demonstrate that entropy-engineered chemical disorder can stabilize robust superconductivity, promote strong flux pinning, and induce correlated electronic behavior, establishing refractory medium-entropy alloys as a promising platform for next-generation superconducting materials.
Superconductivity (cond-mat.supr-con)
Side-Chain Engineering Controls Molecular Packing and Vertical Electron Transport in Discrete n-Type NDI-T2 Oligomers
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Zihao Liu, Hajar Komekoz, Nisarg Trivedi, Max Dorfner, Lokesh Rasabathina, Rico Ehrler, Mike Hambsch, Chen Wang, Dietrich R. T. Zahn, Jörg Matysik, Stefan C. B. Mannsfeld, Carsten Deibel, Olav Hellwig, Frank Ortmann, Michael Sommer, Georgeta Salvan
High-efficiency vertical charge transport in multilayer organic optoelectronic devices highly depends on molecular structure and arrangement. Using two T2-(NDI-T2)2 conjugated oligomers with ethylhexyl (EH) and octyldodecyl (OD) side chains as a model system, their effects on electron transport are investigated using, among other techniques, atomic force microscopy (AFM), conductive atomic force microscopy (C-AFM), grazing-incidence wide-angle X-ray scattering (GIWAXS), steady-state optical spectroscopy, and time-dependent density functional theory (TDDFT) calculations. The oligomers of both materials exhibit relatively disordered structures in the as-cast state, whereas annealing enhances structural order and leads to side-chain-dependent changes in molecular stacking. EH-based films show a smaller annealing-induced photoluminescence shift than OD-based films, suggesting less pronounced stacking and conformational rearrangements, consistent with TDDFT-supported exciton analysis. The current-voltage characteristics are analyzed using the space-charge-limited current (SCLC) model. After annealing, both materials exhibit improved vertical electron mobility. The EH-based films reach a maximum mobility of 1.2 x 10^-4 cm^2 V^-1 s^-1. The combined results suggest that the shorter EH side chains modify the out-of-plane packing environment and facilitate vertical electron transport. These results establish a structure-property relationship between side-chain structure, molecular order, exciton coupling and vertical mobility, providing a molecular design basis for optimising organic semiconductors through side-chain engineering.
Materials Science (cond-mat.mtrl-sci)
19 pages, 5 figures, 3 tables. Supporting Information included as an ancillary PDF
Multifractal Magnons Around Localized Defects
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Adarsh Hullahalli, Yusuf Khand, Christos Panagopoulos, Christina Psaroudaki
Multifractal wavefunctions fluctuate over a hierarchy of spatial scales, remaining spatially extended while exhibiting strongly nonuniform structure. We show that magnons in otherwise crystalline two-dimensional magnets can exhibit such behavior on mesoscopic scales, without disorder or quasiperiodicity. A localized defect can mix discrete groups of nearly degenerate magnon states in a finite sample, generating multiscale interference patterns and multifractal wavefunctions. We demonstrate this mechanism for both a simple spin defect and topological magnetic skyrmions. Large-scale spin-wave calculations for skyrmions in chiral and frustrated magnets reveal clear multifractal diagnostics over the full accessible range of system sizes of above-gap modes. Crucially, skyrmions make these states experimentally observable by hybridizing them with magnetically active internal deformation modes, which gives a subset of the multifractal states a nonzero magnetic dipole moment. These states can therefore be excited by uniform ac fields and remain distinguishable at realistic frequency resolution, providing a direct route to observing mesoscopic magnon multifractality.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
5 pages, 5 figures
Hybrid Monte Carlo for the extended Kane-Mele-Hubbard model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-10-26 20:00 EDT
Finn L. Temmen, Thomas Luu, Johann Ostmeyer, Lin Wang
The Hubbard model offers a powerful minimal description of strongly correlated electrons in molecules and materials, yet it neglects effects observed in nature that give rise to a much richer variety of physics. For instance, including nonlocal interactions introduces a competition between strongly correlated phases, while incorporating spin-orbit coupling (SOC) can lead to the emergence of exotic topological phases. Seeking a more realistic platform for simulating graphene and, potentially, related materials such as transition metal dichalcogenides (TMDs), we therefore consider the extended Kane-Mele-Hubbard model, which features a Kane-Mele SOC term and nearest-neighbor interactions. Simulating this model is particularly challenging once the nonlocal interactions become dominant over the on-site Hubbard interaction, as a severe sign problem arises already at half filling, leaving this regime largely unexplored. In this work, we develop continuous auxiliary field formulations of the model, suitable for treatment with the Hybrid Monte Carlo (HMC) algorithm. Using these formulations, we characterize the sign problem across the model’s parameter space and establish where simulations are feasible, as a first step toward the full phase diagram.
Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Lattice (hep-lat)
9 pages, 3 figures, contribution to the 43rd International Symposium on Lattice Field Theory (LATTICE2026), July 26 - August 1, 2026, University of Maryland, College Park, USA
Divalent Yb in the Ca$_3$Pd$_4$Bi$_8$ Structure Type: Crystal Growth and Physical Properties of Yb$_3$Pd$_4$Bi$_8$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Midori Amano Patino, Sitaram Ramakrishnan, Davide Donadio, Nils Lamouche, Elise Pachoud, Macha Meplan, Daniel Braithwaite, Jean-Pascal Brison, Gerard Lapertot, Andrea Bianchi, Georg Knebel, Valentin Taufour
We report on the single-crystal growth, crystal structure, and physical properties of Yb$ _3$ Pd$ _4$ Bi$ _8$ . Single crystal x-ray diffraction shows that the material crystallizes in the Ca$ _3$ Pd$ _4$ Bi$ _8$ structure-type at ambient conditions, described by orthorhombic symmetry $ Pbam$ . Magnetization measurements reveal a nearly isotropic diamagnetic response, indicating that Yb is stabilized in a non-magnetic divalent configuration. Electrical resistivity measurements show a metallic behavior. First-principles calculations including spin–orbit coupling describe a metal whose states at the Fermi level are dominated by Bi $ 6p$ orbitals, with a density of states within 1% of that of the isoelectronic compound Ca$ _3$ Pd$ _4$ Bi$ _8$ , consistent with a filled and chemically inert $ 4f$ shell. They further show that the nonsymmorphic symmetry of the crystal enforces fourfold-degenerate nodal lines on the Brillouin-zone boundary, four of which cross the Fermi level and give symmetry-enforced Dirac points with a linear transverse dispersion. Despite strong metallic and covalent bonding within the Pd-Bi network, Yb$ _3$ Pd$ _4$ Bi$ _8$ is realized as a rare-earth analog of the Ca$ _3$ Pd$ _4$ Bi$ _8$ structure type with divalent Yb ions. This result offers a potential avenue to discover other rare-earth analogs within this structural family.
Materials Science (cond-mat.mtrl-sci)
10 pages, 7 figures
Effect of oxygen plasma treatment on the structural and superconducting properties of atomic-layer-deposited NbN thin films
New Submission | Superconductivity (cond-mat.supr-con) | 2026-10-26 20:00 EDT
Nitesh Yerra, Mustafa Teke, Felix Otto, Marco Diegel, Detlef Born, Uwe Hübner, Nan Du, Mario Ziegler, Sahitya Varma Vegesna, Heidemarie Krüger
Surface oxidation is a common concern for ultrathin NbN superconducting devices, yet which superconducting properties it affects has not been established for films grown by plasma-enhanced atomic layer deposition. We expose NbN films about 11.4 nm thick to an O$ _2$ plasma for 0 to 60 s, which oxidizes the surface without etching the film, and characterize the same sample series by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and transport measurements on 500 nm wide nanowires. XPS of the surface and the underlying layer shows that the plasma converts the surface to Nb$ _2$ O$ _5$ , whereas the bulk of the treated film is chemically identical to that of the untreated film. Crystalline $ \delta$ -NbN remains intact. During exposure, the total film thickness rises and saturates between 40 and 60 s, indicating self-limiting surface oxide growth. The normal-state resistivity rises by 21% (dc) and 25% (optical) with the plasma dose, while the critical temperature and transition width are unchanged. The switching current densities of 4.9-6.2 MA/cm$ ^2$ at 4.2 K show no systematic dependence on the plasma dose. Their temperature dependence follows the dirty-limit depairing current of Kupriyanov and Lukichev, and the extrapolated switching currents reach 39-46% of the depairing current calculated from the optical resistivity and diffusion coefficient, in agreement with the width dependence reported for nanowires from the same process. The oxygen signature is confined to temperatures near $ T_c$ , where the supercurrent of the treated wires vanishes at least 0.5 K earlier than that of the untreated wire, consistent with a partially oxidized surface layer that acts on the film by the proximity effect. At these doses, oxygen narrows the temperature range of the supercurrent from above but does not systematically reduce the low-temperature current-carrying capacity of the wires.
Superconductivity (cond-mat.supr-con)
Excitonic Stark Response Induced by Quantum Capacitance in van der Waals Heterostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Xiangzhi Hong, Yongkang Jian, Yang Chen, Rukai Cang, Yuanlong Guo, Takashi Taniguchi, Kenji Watanabe, Baigeng Wang, Erfu Liu
Precise electrostatic control in van der Waals heterostructures is commonly described by a geometric capacitor model, which assumes that the internal electric field is fully determined by external gate voltages. Here, we show that this description breaks down in the presence of interfacial charge transfer, where quantum capacitance modifies the internal electrostatics. Using interlayer excitons as local probes, we observe a dipole-dependent energy splitting that persists even when the gate-induced geometric field is nominally canceled. This splitting reflects incomplete cancellation between gate- and carrier-induced fields set by quantum capacitance, while many-body renormalization is largely symmetric with respect to the two opposite dipole orientations, allowing the splitting to provide a direct optical measure of the local chemical potential. Our results reveal the central role of quantum capacitance in interface electrostatics and provide a route to probe it in operando.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Modification of optical properties in ultrathin ALD-grown NbN layers using oxygen plasma treatment
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Mustafa Teke, Nitesh Yerra, Alireza Sadeghi, Mario Ziegler, Detlef Born, Nan Du, Marco Diegel, Uwe Hübner, Sahitya V. Vegesna, Heidemarie Krüger
NbN thin films with a nominal thickness of 10 nm were grown by atomic layer deposition (ALD) on Al$ _2$ O$ _3$ -buffered Si substrates and treated with oxygen plasma for 0 s (untreated), 20 s, 40 s, and 60 s to investigate oxygen-induced changes in their optical properties. Spectroscopic ellipsometry (SE) measurements were performed before and after oxygen plasma treatment over the ultraviolet-visible-near-infrared (1.24-6.20 eV) and infrared (0.041-0.827 eV) spectral ranges. Film thickness determined by X-ray reflectivity (XRR) was used as a fixed parameter in the optical modeling to extract the dielectric function, optical constants, and effective free-carrier concentration. We observed the emergence of a distinct absorption feature near 4.9 eV following oxygen plasma treatment, consistent with the oxidation of the NbN surface and the resulting change in its optical properties. Increasing the treatment time from 0 to 60 s reduced the effective carrier concentration from $ 1.20 \times 10^{22}$ to $ 1.03 \times 10^{22}$ cm$ ^{-3}$ and the effective carrier mobility from 2.44 to 2.27 cm$ ^2$ V$ ^{-1}$ s$ ^{-1}$ . The obtained results provide a basis for understanding the effects of oxygen plasma treatment on NbN thin films.
Materials Science (cond-mat.mtrl-sci)
Magnetic Anisotropy and Magnetization Dynamics in Si/Ni Multilayers Probed by FMR and VSM Magnetometry
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Dushyant Singh, Subha Maity, Tharundev V V, Subhavenkadesh SS, Vigneshwari SR, Krista R. Khiangte
The magnetic anisotropy and magnetization dynamics of sputtered [Si(40Å)/Ni($ t_{\mathrm{Ni}}$ ~Å)]$ _{20}$ multilayers were systematically investigated at room temperature using SQUID–VSM magnetometry and angle-dependent ferromagnetic resonance (FMR). Static measurements reveal soft ferromagnetic behaviour in thicker Ni layers and mixed ferromagnetic and superparamagnetic contributions at reduced thicknesses. The saturation magnetization increases toward the bulk Ni value with increasing thickness, consistent with Ni nanocrystallite growth. Magnetic dead-layer analysis yields an interfacial dead-layer thickness of approximately $ 9$ ~Å per interface, accounting for the suppressed magnetization in thinner Ni layers. Angle-dependent FMR measurements reveal effective easy-plane magnetic anisotropy, while out-of-plane spectra exhibit additional non-uniform spin-wave modes. The effective magnetization remains lower than the static saturation magnetization, indicating a perpendicular anisotropy contribution that partially compensates the demagnetizing field. Quantitative anisotropy analysis yields an interfacial anisotropy constant of $ K_S = +0.17\mathrm{erg,cm^{-2}}$ , favouring perpendicular magnetization, and a volume anisotropy constant of $ K_V = -1.23 \times 10^6~\mathrm{erg,cm^{-3}}$ , favouring in-plane alignment, with an extrapolated anisotropy crossover thickness of $ t_c \approx 27$ ~Å. Increasing FMR line-shape asymmetry with decreasing Ni thickness is consistent with enhanced interfacial roughness. These findings highlight the competing interfacial and volume anisotropies and the importance of Ni thickness and interface quality in tailoring Si/Ni multilayers for silicon-compatible spintronic applications.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
High-quality, deep formation and identification of oxygen-vacancy defects in silicon carbide
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Ryo Shiotani, Fu-Chieh Chuang, Mitsuaki Kaneko, Tetsuri Nishikawa, Hiroshi Abe, Taiga Matsuoka, Shigehito Miki, Kazuki Okajima, Takeshi Ohshima, Yoshihiko Kanemitsu, Tsunenobu Kimoto, Naoya Morioka, Norikazu Mizuochi
Optically addressable paramagnetic defects in silicon carbide (SiC) are attractive for scalable quantum technologies such as quantum sensing. PL5, PL6, and PL7 are promising defects for their high brightness and spin-readout contrast. Although generation by oxygen implantation has been reported very recently, nonuniform spin and optical properties and the limited generation depth of implanted defects hinder both high-sensitivity sensing and conclusive microscopic identification. Here we engineer high-quality defects by decoupling oxygen incorporation and defect formation, realizing highly homogeneous spin-resonance frequencies as well as narrow optical linewidths and long T2\ast coherence time. Further, we demonstrate defect formation beyond the ion range utilizing oxygen diffusion, exceptional among impurities in SiC. We further provide hyperfine-interaction statistics of 17O and host nuclei across many PL6 defects, making the oxygen-vacancy origin conclusive. Together, the microscopic identification and the demonstrated formation route establish a foundation for developing the oxygen-vacancy spin defect into a versatile quantum platform.
Materials Science (cond-mat.mtrl-sci), Quantum Physics (quant-ph)
18 pages, 5 figures, includes Supplementary Information
Probing the limits of forward screening and inverse design of crystal materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Zhilong Song, Zijun Pang, Lixue Cheng
Crystal materials are designed either by screening known crystals for a target property or by generating new crystals with that property. Both routes are judged against public databases of known crystals, but these databases name the same crystal differently. Several materials announced as new by recent generative and autonomous discovery campaigns have since proved to be known phases or close variants of them. The limits of both routes remain unmeasured. Here we probe them by matching the crystals of 55 databases by structure into one self-extending database of 14.6 million crystals and 131.8 million property values, each traced to its source. Only 4.5% of its crystal-property pairs carry a value. To fill the empty pairs, we developed CGTNet, an equivariant graph transformer with state-of-the-art accuracy on several tasks of two public benchmarks. Trained on each task, it forms a library of property models whose predictions we release. The reach of forward screening has been underestimated. Known crystals hold tens of thousands of ultra-incompressible candidates without a recorded bulk modulus, and a post hoc audit of synthesis evidence finds among them ReN2, whose bulk modulus was measured at 428 GPa. The novelty claimed for inverse design has been overestimated. At an equal verification budget, a stiffness-conditioned generator returned more stiff hits than screening (100 versus 55), but all contained osmium and 82 repeated recorded compositions. Integrating and completing the databases of known crystals therefore moves the limits of both routes: it widens what screening can reach and sets the reference against which generated crystals are judged new.
Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG)
23 pages, 5 figures
Stochastic and quantum autonomous information machine: efficiency fluctuations, precision and optimization
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-10-26 20:00 EDT
We investigate the conversion between thermal and informational resources in an autonomous machine coupled to thermal reservoirs and a tape, playing the role of an information reservoir. The machine is able to perform information erasure driven by heat, and information-powered refrigeration, for which we introduce suitable efficiency definitions. We focus on the role of fluctuations in the currents and stochastic efficiencies, as well as in operation at optimal performance. The model is also extended to allow a coherent information reservoir, which is able to modify operation and performance. All in all, our work provides insights for the design and optimization of information-to-work conversion devices at small scales.
Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
20 pages, 7 figures
Discrete WKB approach to density profiles in inhomogeneous two-band free-fermion chains
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-10-26 20:00 EDT
Federico Finkel, Artemio González-López, Martín Zapata
We extend the discrete WKB method to one-dimensional bipartite tight-binding chains of free fermions with slowly varying hopping amplitudes and on-site potentials. We focus on the inhomogeneous Rice-Mele model, suggesting possible experimental realizations thereof in optical superlattices. We derive explicit semiclassical expressions for the single-particle wave functions and density of states, as well as the sublattice-resolved local particle densities and filling fraction at arbitrary Fermi energy. In particular, we show that the WKB density profiles agree with those obtained from the local-density approximation. We analyze the spatial dependence of the local band edges and its consequences for the global spectral structure, and clarify the role played by the phase-space topology in determining the Bohr-Sommerfeld quantization conditions. Finally, we illustrate our results with two representative examples: a homogeneous Rice-Mele chain subject to a harmonic trap and a fully inhomogeneous chain containing a domain wall.
Strongly Correlated Electrons (cond-mat.str-el), Mathematical Physics (math-ph), Quantum Physics (quant-ph)
42 pages, 10 figures
On the Spontaneous Structural Reconstructions of Chalcogen-Depleted MoS$_2$, MoSe$_2$, and Janus MoSSe Monolayers
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Bruno Ipaves, Guilherme S. L. Fabris, Raphael B. Oliveira, Pulickel M. Ajayan, Marcelo L. Pereira Junior, Douglas S. Galvão
Removing one chalcogen layer from a transition-metal dichalcogenide monolayer leaves an undercoordinated sheet that reconstructs as the remaining chalcogen atoms cross the metal plane. Here, we combine \textit{ab initio} and reactive molecular dynamics (MD) simulations of depleted MoS$ _2$ , MoSe$ _2$ , and Janus MoSSe, examining each remaining chalcogen on two parent lattices, to show that the remaining chalcogen type determines the structural reconstruction, with only a minor influence from the parent lattice. In \textit{ab initio} trajectories of the Janus-derived sheets, Se crosses the Mo plane already at 300K, whereas S stays in place at 300K and the sheet reconstructs only at 900K. With a free in-plane cell, the crossings precede an anisotropic lattice contraction, which therefore results from the structural reconstruction. Reactive MD simulations of 50nm sheets show that, when S remains, the Mo lattice stays crystalline in nanometric domains that disappear with time and temperature, with pores/holes at 900~K. In contrast, when Se remains, the Mo lattice loses crystalline order within the first picosecond, and 36–39% of the Se atoms cross at every temperature. In a depleted lateral MoS$ _2$ /MoSe$ _2$ heterostructure, both modes coexist in one sheet, each half reconstructing like its single-chalcogen counterpart, suggesting chalcogen patterning as a route to define crystalline and disordered regions in a single monolayer.
Materials Science (cond-mat.mtrl-sci)
Machine Learning Accelerated Simulation of Charge Regulation Effects
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-10-26 20:00 EDT
Vijay Yadav, Sunita Kumari, Prabhat K. Jaiswal
Many solvated materials, from nanoparticles to polyelectrolytes, acquire charge through the dissociation or association of surface groups, a phenomenon known as charge regulation (CR). Recent methods use hybrid charge regulation Monte Carlo (CR-MC)/molecular dynamics (MD) to evolve the system while dynamically adjusting charges on the surface groups. However, this approach is computationally expensive, as Monte Carlo sampling can be as costly as the accompanying MD. In this work, we introduce charge regulation machine learning (CR-ML), a graph attention network that predicts the ionization probability of every surface site from the instantaneous configuration, the dissociation constant of surface groups, and the solution conditions. We show that CR-ML reproduces the equilibrium conformations and degree of ionization obtained with CR-MC for a hydrophobic polyanion. We further test CR-ML on the more complex system of two nanoparticles mediated by a polyelectrolyte, where it accurately predicts the charge asymmetry that develops between the two particles. Across these systems, CR-ML updates charges an order of magnitude faster than CR-MC while accurately reproducing its equilibrium properties. This framework opens a path toward large-scale simulations of charge-regulating materials for understanding and designing their responsive behavior.
Soft Condensed Matter (cond-mat.soft)
14 pages and 7 figures
Nano-ARPES observation of a flat band at the \bar{M} point in 2.4° twisted bilayer graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Giovanna Feraco, Przemysław Przybysz, Oreste De Luca, Ying Wang, Pavel Dudin, José Avila, Jianting Ye, Paweł Dąbrowski, Paweł J. Kowalczyk, Jagoda Sławińska, Petra Rudolf, Antonija Grubišić-Čabo
The emergence of flat bands in twisted bilayer graphene at the so-called magic angle reveals a range of intriguing phases, such as superconductivity and Mott insulating states, resulting from electrons entering a correlated state. This establishes twisted bilayer graphene as an excellent platform for exploring correlation effects in many-body phases and across various twist angles. However, in most cases, the twist angle is not an easy parameter to control because it exhibits structural instabilities such as relaxation and reconstruction that reduce the correlation effects. Here, we report the unexpected appearance of a flat band at the \bar{M} point far from the Fermi level in a 2.4° twisted bilayer graphene, directly visualized by angle-resolved photoemission spectroscopy. Our work is the first observation of flat bands away from the \bar{K} point in twisted bilayer graphene and highlights the need to probe the entire Brillouin zone to fully capture electronic states in twisted structures.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Main text (11 pages , 4 figures) and supplementary material (3 pages, 3 figures)
Controlled Fabrication of Uniform Columnar Porous GaN Architectures by Electrochemical Etching
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Thom R. Harris-Lee, Ben Thornley, Jiawei Zhang, Martin Frentrup, Simon Fairclough, Menno J. Kappers, Rachel A. Oliver
Electrochemical etching (ECE) of n-type c-plane GaN enables the formation of porous architectures capable of enhancing the performance of optoelectronic devices and broadening the range of possible GaN applications. Here, we demonstrate that the addition of NaOH to Na2C2O4 (and other non-acidic etchant solutions) directs ECE toward the formation of nanoscale, vertically aligned, highly uniform columnar pore morphologies with relatively limited surface roughening. By varying the NaOH concentration within mixed electrolyte systems, the columnar pore shape, diameter, spacing, and bulk and surface porosity can be readily tuned. In addition to manually mixing NaOH with another etchant, aqueous basic electrolytes such as Na2CO3 and Na3PO4, each inherently containing significant hydroxide concentration through hydrolysis, also produce similar columnar pore morphologies, indicating that hydroxide plays the key role in directing the vertical pore growth. Chronoamperometry and pore structure analysis reveals that the mixed hydroxide-containing electrolyte systems exhibit a distinct, new ECE mechanism rather than a simple superposition of the individual ECE behaviour of each anion present. This work provides significant insight into the ECE mechanism for porous GaN, which is proposed to contain multiple reaction steps where hydroxide anions are involved in the formation of a reactive intermediate. These findings establish a versatile and controllable route for engineering columnar porous GaN architectures, offering significant advancement in applications requiring high porosity, ordered, and bespoke structures.
Materials Science (cond-mat.mtrl-sci)
22 pages, 7 figures
First- and Second-Order Electron Position Correlators Reveal Topological Phase Transitions
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Antimo Marrazzo, Christian Loer Llemit, Massimo Capone
The theory of conventional critical phenomena is built around the concepts of fluctuations and correlators of local observables. Here, we show that topological phase transitions can also be characterized through spatial and temporal two-point correlation functions associated with fluctuations of the electronic position operator. The key object is the antisymmetric part of the position-position correlation function, which yields the Chern number in the equal-time and equal-space limit. When the system is translationally invariant in space or time (the latter case corresponding to an equilibrium condition), these two-point correlators reduce to one-variable functions of the remaining variable. Remarkably, these functions are both reminiscent of critical behaviour, including divergent correlation times and lengths signalling the phase transitions. Away from these conditions, namely in non-periodic systems or genuinely dynamical processes, criticality is instead better captured by higher-order Chern-Chern correlators constructed from local or dynamical markers obtained as coincident-point limits of the position correlators. These higher-order Chern-Chern correlators can be seen as double Levi-Civita contractions of second-order position correlators, selecting the antisymmetric sector in each index pair. We substantiate this framework through numerical simulations and analytic calculations. Our results establish a general correlator-based description of topological phase transitions, applicable to crystalline, noncrystalline, equilibrium, and dynamical systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Disordered Systems and Neural Networks (cond-mat.dis-nn), Materials Science (cond-mat.mtrl-sci), Statistical Mechanics (cond-mat.stat-mech)
10 pages, 5 figures
Tensor Networks for Materials Simulation and Quantum Chemistry
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-10-26 20:00 EDT
Saeed S. Jahromi, Augustine Kshetrimayum, Roman Rausch, Sukhbinder Singh, Roman Orus
Predicting the properties of correlated materials and molecules often requires a many-body description that goes beyond single-particle and mean-field approximations. Tensor networks address this challenge by exploiting the entanglement structure of quantum states to construct compact, systematically improvable representations. Although developed largely for idealized model Hamiltonians, these methods are increasingly being integrated into material-specific calculations. This Perspective introduces their underlying principles and examines how network geometry, bond-dimension truncation, and approximate contraction determine the accuracy and computational reach of these approaches. We survey applications across regimes of increasing complexity, ranging from ground-state properties of quantum magnets and itinerant-fermion systems to excitation spectra, nonequilibrium dynamics, finite-temperature and open systems, and molecular electronic structure. We then examine four routes connecting these methods to real materials, including experimentally constrained models, downfolded Hamiltonians, dynamical mean-field theory with tensor network impurity solvers, and quantum embedding. Throughout, we evaluate the maturity of existing capabilities and their principal limitations, synthesizing this assessment into a practical method-selection guide. We argue that reliable materials predictions require quantifying uncertainties introduced at each stage, from constructing material-specific Hamiltonians to extracting experimentally accessible observables. Finally, we identify the algorithmic advances and reproducible computational practices needed to establish tensor networks as a routine tool for predictive materials science and quantum chemistry.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
28 pages, 4 figures
Spontaneous Decay of High Energy Composite Fermions
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
An electron, when added to a fractional quantum Hall fluid, famously splits into fractionally charged composite-fermion quasiparticles. We show here that a high energy composite fermion carrying a fractional charge decays into a collection of particles, including quasiparticles, quasiholes, and even whole electrons.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
Floquet Engineering of Momentum Gaps in Magnonic Time Crystals: Slow-Drive Amplification and In-Gap Propagation
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Paweł Gruszecki, Victor Pacheco-Peña
Photonic time crystals host momentum gaps in which waves grow exponentially but cannot propagate. We establish their magnonic counterpart in a thin film with periodically switched anisotropy, deriving its Floquet band structure and confirming it micromagnetically. Gaps require a precession-ellipticity contrast. The waveform controls high-order gaps: a single 1GHz switching drive amplifies a comb of spin-wave bands, from 2.5 to 4.5GHz, above Gilbert losses even with smoothed edges, unlike sinusoidal modulation. With the Dzyaloshinskii–Moriya interaction, amplified packets propagate inside the gap while growing.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Majorana Edge-to-bound State Transition in Interferometric Superconductor Rings
New Submission | Superconductivity (cond-mat.supr-con) | 2026-10-26 20:00 EDT
Xiangyu Bi, Aoshen Yang, Hongzi Cao, Ganyu Chen, Yuqiang Fang, Zeya Li, Qizheng Sun, Junwei Huang, Da Wang, Fuqiang Huang, Toshiya Ideue, Qianghua Wang, Yoshihiro Iwasa, Hongtao Yuan
Manipulating flux quanta in topological superconductors is central to vortex braiding in quantum computing. Their interferometric superconducting rings can host either topologically protected edge states with fluxes confined inside the central hollow area or vortex bound states in flux cores at the annulus walls. Here we demonstrate a strategy to drive topological edge states into vortex bound states by tuning the relative scale of vortex size and annulus width in nano-ring interferometric device on 2M-WS$ _2$ topological superconductor. Near its superconducting transition where the coherence length exceeds the annulus width, Little-Parks oscillations exhibit expected periods for flux bundles in ring-center, consistent with edge states residing at inner and outer rims of the annulus. Upon cooling, where the coherence length shrinks below the annulus width, the unexpectedly increased oscillation period reflects multiple fluxes distributed along annulus region in flux necklace configuration, implying a transition from extended edge states to localized vortex bound states. Ginzburg-Landau simulations and local density-of-states calculations with Bogoliubov-de Gennes equations reveal that large values for both Ginzburg-Landau parameter and flux-pinning energy are vital for such a transition. Our findings provide a novel strategy for understanding flux manipulation towards flux braiding and topological quantum computing.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
Generalization properties of the token perceptron: the role of embedding and vocabulary
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2026-10-26 20:00 EDT
Dario Bocchi, Matteo Negri, Flavio Nicoletti, Francesco D’Amico
Large language models are trained to predict tokens from a finite vocabulary, each represented by a vector in a $ d$ -dimensional embedding space. Therefore, token prediction is a classification problem whose classes have a geometry determined by the embedding. We study how this geometry affects learning in a minimal solvable model: a linear predictor that maps a sequence of $ N$ embedded tokens to a $ d$ -dimensional output through one $ d\times d$ matrix per position, trained in the teacher–student setting. We call this the \textit{token perceptron}. We compute its generalization error with the replica method, taking $ N\to\infty$ at fixed number of examples per position $ \alpha=P/N$ and keeping $ d$ and the vocabulary size $ D$ finite. As a first reference case, we consider continuous embeddings on the sphere, which isolate the role of the embedding dimension. The natural load is then $ \alpha/d$ , and for $ d>1$ a normalized label fixes the direction of the teacher output, so the problem becomes a noiseless regression: the teacher is recovered exactly above $ \alpha_{\rm rec}=d^2/(d-1)$ , and spherical cross-entropy reaches this threshold at large inverse temperature. In the same setting the storage capacity of random associations scales as $ d^2$ for margins $ O(1/\sqrt{d})$ . We then turn to vocabulary embeddings, where a label only identifies the Voronoi cell of the teacher output, so that each example imposes inequalities rather than equations, as in the classical perceptron. We compute the Bayes-optimal error for a given embedding matrix through an approximate spectral closure and show that the optimal learner first resolves the directions in which the vocabulary has the largest variance, even when the teacher is isotropic.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech), Machine Learning (cs.LG), Machine Learning (stat.ML)
39 pages, 9 figures
Ginzburg-Landau Theory with Elastic Incompatibility Describes the Liquid-G-phase-Crystal State Diagram
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Alessio Zaccone, Konrad Samwer
We derive a mechanically consistent Ginzburg-Landau theory for the metastable heterogeneous G state reported in deeply undercooled metallic liquids. The central result is that type-II-like mixed-state physics can emerge structurally with the random internal stress field playing the role of the magnetic field. Frozen eigenstrain due to elastic incompatibility between ordered cores and the amorphous matrix generates incompatible stress, while the non-affine internal strain in the liquid-like matrix in between the ordered cores relaxes that stress over a finite screening length $ \lambda_\sigma$ (analogous to the London length in the superconducting problem). Structural order heals over a distinct mechanically-dressed length $ \xi_G$ ; their ratio $ \kappa_G=\lambda_\sigma/\xi_G$ provides the structural counterpart of the Ginzburg-Landau parameter. Because the matrix is transiently rigid yet locally relaxational only over an intermediate time window, the same mechanism selects crystal for slow protocols, a heterogeneous G state at intermediate rates, and a homogeneous L-like glass under rapid arrest. Residual incompatibility frustrates coarsening, allowing finite ordered cores and screened, orientation-dependent core interactions. The resulting texture is an inverted Abrikosov analogue: structural order resides in the cores, whereas incompatible-stress screening is carried by the surrounding disordered matrix. The theory yields direct simulation and experimental tests through stress-decay, structural-healing, non-affine-susceptibility, and kinetic measurements.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other), Soft Condensed Matter (cond-mat.soft), Superconductivity (cond-mat.supr-con), Applied Physics (physics.app-ph)
Unconventional charge density wave order in ErTe$_{3}$: symmetry breakings and fluctuations probed by Raman scattering
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2026-10-26 20:00 EDT
Théotime Freitas, Mattia Udina, Alexandr Alekhin, Niloufar Nilforoushan, Sarah Houver, Alain Sacuto, Benito A. Gonzalez, Ian R. Fisher, Indranil Paul, Yann Gallais
Recent experiments have revealed unexpected mirror-symmetry breakings in the charge density-wave (CDW) state of rare-earth tritellurides, suggesting a putative ferro-axial CDW state. Here we report polarization-resolved Raman scattering measurements tracking the point-group symmetry breakings across the CDW phase transition in the rare-earth tritelluride ErTe$ 3$ . We show that the mirror-symmetry breakings follow closely the emergence of the CDW order, suggesting a single component CDW order parameter. Furthermore, Raman measurements in the $ A{2g}$ symmetry channel above the CDW transition temperature indicate the absence of significant ferro-axial fluctuations. We discuss the broad implications of these findings with respect to the nature of the CDW state in the tritellurides.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
to appear in JPS Conference Proceedings
Finite-Temperature Transconductance of Multiterminal Josephson Junctions with Topological Andreev Spectra
New Submission | Superconductivity (cond-mat.supr-con) | 2026-10-26 20:00 EDT
Gleb S. Seleznev, David C. Ohnmacht, Wolfgang Belzig
Multiterminal Josephson junctions (MTJJs) provide a controllable platform for engineering topological Andreev spectra. At zero temperature, Andreev bound states (ABSs) with nonzero Chern numbers give rise to quantized transconductance between superconducting terminals. We derive the finite-temperature transconductance of MTJJs using linear-response theory. We first demonstrate the destructive role of temperature: changes in the thermal occupations of the ABSs destroy exact transconductance quantization. We then show that finite temperature can also play a constructive role by making the transconductance sensitive to finite-energy topological crossings hidden from the zero-temperature response. Our results establish the thermal limitations of transconductance quantization and identify finite-temperature transport as a probe of otherwise inaccessible topology in Andreev spectra.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Magnons and excitons from Bethe-Salpeter equation and its application to graphene-based magnets
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Simran Chourasia, Maurício F. C. Martins Quintela, J. J. Palacios
With the recent isolation of two-dimensional semiconducting magnetic materials, the theoretical study of spin-flip collective excitations (magnons) along with spin-conserving electron-hole bound pairs (excitons) has become particularly relevant. Describing both types of quasiparticles within the same theoretical framework is possible, in principle, but the well-established many-body formalism for the calculation of excitons, based on the intertwined Bethe-Salpeter and Hedin’s equations, is not satisfactory for magnons, since the usual approximations produce a spurious gapped Goldstone mode. Here, we show that excitons and magnons can be computed on the same footing under the same Bethe-Salpeter formalism, while respecting the gapless Goldstone mode for magnons. We demonstrate how this can be achieved through the evaluation of the full Bethe-Salpeter equation, beyond the Tamm-Dancoff approximation in model Hamiltonians. As an example, we apply it to ferromagnetic and antiferromagnetic graphene, faithfully represented by the extended Hubbard model. Our results clarify the roles of on-site and non-local interactions in exciton and magnon appearance and identify consistency requirements relevant to extending the approach to first-principles calculations.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
16 pages, 9 figures
Field Directed Assembly of Anisotropic Composite Pacman Colloids into Reconfigurable Architectures
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-10-26 20:00 EDT
Indira Barros, Isha Songara, Indrani Chakraborty
We investigate the field-directed assembly of patchy colloidal particles composed of magnetic hematite cubes encapsulated in TPM shells. These Pacman-like particles exhibit specific interactions via their magnetic patch, enabling tunable structures under external fields. A magnetic field drives patch-to-patch interactions, while an AC electric field induces stacking and spreading. By using this multi-field combination and by varying field parameters, such as frequency and amplitude, we achieve programmable transitions between distinct assembly modes. Our work offers a versatile platform for designing reconfigurable colloidal architectures with potential applications in micro-robotics and smart materials.
Soft Condensed Matter (cond-mat.soft)
Time-temperature superposition from multi-temperature chirp rheometry of thermorheologically simple materials via physics-informed Gaussian processes
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-10-26 20:00 EDT
Isaac Y. Miranda-Valdez, Kourosh Mobredi, Juha Koivisto, Mikko J. Alava
Inferring constitutive laws from transient response data is a central inverse problem in soft condensed-matter physics, particularly when the relevant relaxation spectrum extends beyond the time window of a single experiment. Time-temperature superposition (TTS) constrains this problem for thermorheologically simple materials in the linear viscoelastic regime by allowing temperature to rescale the characteristic relaxation time without changing the underlying shape of the relaxation spectrum. We incorporate this constraint into a physics-informed machine-learning framework for time-resolved mechanical spectroscopy via chirp rheometry. We encode compact fractional viscoelastic models as causal convolutional features derived from the Boltzmann superposition principle, and we jointly fit multi-temperature chirp records using sparse variational Gaussian process regression. The model infers horizontal shift factors, constitutive parameters, and an observational-noise scale directly from time-domain stress-strain signals measured in the linear viscoelastic regime, without first extracting frequency-domain spectra or manually shifting separate curves. For synthetic Fractional Maxwell data, the method recovers the generating constitutive law from a prescribed model library and latent shifts over stress-noise levels from 3% to 25%. Applied to a DGEBA-IPDA epoxy dataset spanning the glass-transition regime, the pooled likelihood distinguishes competing fractional rheology models using the Bayesian information criterion. These results recast TTS master-curve construction as probabilistic inference over latent time rescaling and linear viscoelasticity, while also identifying limitations, such as homoscedastic noise and weakly informative spectral regimes.
Soft Condensed Matter (cond-mat.soft)
Configuration-Independent Low-Energy Gaps in Graphene Nanoribbons: A $δ$-Scatterer Transfer-Matrix Approach
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
C.I. Ávila-Joachín, J.C. Sandoval-Santana, Pedro Pereyra
Transport measurements on lithographically patterned graphene nanoribbons suggest that the gap depends primarily on ribbon width rather than on crystallographic edge orientation, in contrast to predictions of ideal tight-binding models. To address this, we develop a transfer-matrix approach, based on the theory of finite periodic systems, in which each carbon atom of the honeycomb lattice is represented by an individual $ \delta$ -scatterer with interaction strength $ \gamma^{}{\delta}$ and the nanoribbon is treated as a confined multichannel finite periodic system. We derive the unit-cell transfer matrix for both arm-chair and zig-zag edge configurations and obtain the transmission and channel-coupling coefficients in closed form. The transmission spectra display the resonant band structure characteristic of finite periodic systems, with the number of resonances per allowed band increasing with the number of unit cells. For $ \gamma{\delta}=0$ the ribbons are fully transparent; for $ \gamma_{\delta}>0$ a low-energy transport gap opens and grows linearly with the scatterer strength, $ \Delta=0.364265,\gamma_{\delta}$ , identically for arm-chair and zig-zag edges. These results are consistent with the reported absence of a systematic dependence on orientation, while the analytical results show that interchannel coupling vanishes exactly for arm-chair ribbons and decreases with increasing width for zig-zag ribbons, revealing the role of edge geometry. Together, these findings indicate that atomic-scale scattering, represented by the $ \delta$ -potential formalism, provides a common orientation-independent contribution to the low-energy transport gap in the pristine ribbons considered here.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Other Condensed Matter (cond-mat.other)
Rationalizing charge transfer: a single-molecule case study across three distinct surfaces
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Benjamin Lowe, Jan Berger, Martin Ondráček, Oleksandr Stetsovych, Shayan Louie, Marco Lozano, Diego Soler-Polo, Shiladitya Karmarkar, Andrés Pinar Solé, Iva Plutnarová, Pingo Mutombo, Manish Kumar, Michael Píro, Ali Cem Demirok, Michael L. Steigerwald, Zdeněk Sofer, Colin Nuckolls, Pavel Jelínek
Organic molecules are versatile building blocks for the formation of complex low-dimensional nanostructures on surfaces. Recently, interest has grown in translating on-surface synthetic protocols from noble metal surfaces to insulating surfaces, which offer technological relevance, and to magnetic or superconducting surfaces, which offer new routes to correlated phases. It is important, therefore, to understand how these alternative surfaces may alter the properties of adsorbates through processes like charge transfer and screening. Evidence for charge transfer is often obtained experimentally via scanning tunneling microscopy (STM) and spectroscopy (STS), and theoretically via density functional theory (DFT). In this work, we systematically compare the properties of isolated macrocyclic emeraldine (Me$ _6$ ) molecules on three different surfaces: metallic Au(111), a semiconducting ferromagnetic monolayer of FeCl$ _2$ , and a cleaved superconducting surface of bulk 2H-NbSe$ _2$ . We show that STS and DFT alone are insufficient to quantify charge transfer for these cases. Instead, we complement these methods with Kelvin probe force microscopy (KPFM) measurements and model Hamiltonian calculations to demonstrate that on Au(111) and FeCl$ _2$ , Me$ _6$ molecules donate a single electron to the substrate, whereas on NbSe$ _2$ two electrons are transferred from molecule to substrate. Our work provides insight into the interplay of charge transfer, screening, and molecule-substrate coupling, and develops experimental and theoretical methods for comparing the properties of adsorbates across different surfaces for future studies.
Materials Science (cond-mat.mtrl-sci)
32 pages, 5 figures
Combining Simulations and Spectroscopy to Design Protective Coatings on Sulfide Solid Electrolytes
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Zhiyi Wang, Leonie Braks, Michele Ceriotti, Ali Coskun, Hanna Türk, Davide Tisi
Sulfide solid electrolytes are attractive for all-solid-state batteries because of their high Li-ion conductivity and favorable processability, but their practical use is limited by electrochemical instability and moisture-induced degradation. Molecular surface coatings offer a scalable strategy to improve humidity tolerance and interfacial stability, yet there is limited understanding of the molecular-level factors governing surface interactions. By combining large-scale atomistic simulations enabled by a machine-learning potential with targeted experiments, we present a comprehensive framework for designing molecular coatings on Li$ _6$ PS$ _5$ Cl (LPSCl). Using a PET-MAD interatomic potential fine-tuned on an r$ ^2$ SCAN reference dataset covering LPSCl surfaces, molecular adsorbates, and their interactions, we model surface adsorption of carboxylic (CA), sulfonic (SA), and phosphonic (PA) acids with alkyl chains of varying lengths and the interaction of these coated surfaces with water at finite temperature. The simulations show that lithiated head groups generally exhibit more favorable adsorption energies. Impedance spectroscopy shows that the lithiated coatings maintain 40–55% of the initial ionic conductivity after powder processing. While adsorption strength is largely controlled by head-group chemistry and lithiation state, coating morphology depends primarily on alkyl-chain length and surface coverage. In particular, long-chain lithiated carboxylates form dense, brush-like hydrophobic layers that reduce water access to reactive Li surface sites, with protection setting in at a coating thickness of approximately 0.8 nm. Consistent with these predictions, longer carboxylate chains suppress H$ _2$ S evolution more effectively. Because thicker coatings also hinder Li-ion transport, intermediate chain lengths offer the best balance between moisture protection and ionic conductivity.
Materials Science (cond-mat.mtrl-sci)
15 pages main paper, 22 pages SI
Folding of Free Polymers Under Confinement by Responsive Hydrogels
New Submission | Soft Condensed Matter (cond-mat.soft) | 2026-10-26 20:00 EDT
Controlling the folding of biopolymers in crowded and confined environments, such as the interior of biological cells, remains a significant challenge. Macromolecular crowding and spatial confinement can strongly influence transition pathways between folded and unfolded states of proteins. Such environments can be mimicked in experiments by confining polymers within soft, tunable media, such as hydrogels – cross-linked polymer networks that swell by absorbing solvent and exhibit stimulus-dependent responsiveness. Here, we develop a self-consistent mean-field theory for the equilibrium swelling and internal composition of a hydrogel immersed in a solution of free polymer coils. The theory extends the Flory-Rehner framework by incorporating free polymer coils, modeled as fluctuating ellipsoids, whose sizes and shapes are characterized by the eigenvalues of the gyration tensor. Confinement of the coils within gel pores is characterized by an effective free-volume fraction, parametrized from numerical calculations for self-avoiding-walk chains between hard walls. Coupled chemical potential equilibrium conditions are solved numerically over ranges of coil molecular weight and free polymer concentration. We find that free polymers drive a non-monotonic swelling response of hydrogels, with osmotic swelling at low concentrations followed by deswelling at higher concentrations, in qualitative agreement with experiment. We further demonstrate that confinement within gel pores reduces the radius of gyration and asphericity of embedded polymer coils, driving them toward compact, globular conformations analogous to folded protein states. These results establish a theoretical foundation for using responsive hydrogels as tunable, artificial chaperone-like systems capable of inducing and controlling biopolymer folding.
Soft Condensed Matter (cond-mat.soft)
14 pages, 11 figures
CO2-Induced Shifts in the Confined Phase Transformation of CH4 in Metal-Organic Frameworks
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Anthony Dorhauer, Bartosz Mazur, Bogdan Kuchta, Carlos Wexler
A sharp increase in gas uptake over a narrow pressure range can occur for fluids confined in nanoporous materials such as metal-organic frameworks (MOFs), reflecting a transformation between distinct adsorption states, often accompanied by the existence of metastable states. Understanding how co-adsorbed species modify this behavior is important for predicting and optimizing gas storage and separation. Here, we investigate the effect of CO2 on the adsorption transformation of confined CH4 in rigid IRMOF-1 and IRMOF-8. Transition-Matrix Monte Carlo (TMMC) simulations were performed for systems containing 0-75 and 0-150 CO2 molecules in IRMOF-1 and IRMOF-8, respectively. While the addition of CO2 decreases the maximum CH4 uptake, consistent with competition for pore space, remarkably, the presence of CO2 significantly shifts the discontinuity in the CH4 adsorption isotherm to substantially lower pressures relative to the pure CH4 system. This promotion of the high-density CH4 phase at lower pressures demonstrates that CO2 substantially alters the thermodynamic landscape governing confined CH4 through changes in both fluid-fluid and fluid-framework interactions. These results establish CO2 as a thermodynamic modifier of confined CH4 behavior and suggest that controlled co-adsorption provides a means of tuning adsorption transformations in nanoporous materials.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
Supplemental Information and Input files available upon request. Under review (ACS Omega)
Extended Hydrodynamics of Planar Heisenberg Ferromagnetic Systems
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2026-10-26 20:00 EDT
Dwigbijoy Paul, Sreedhar B. Dutta
Access to hydro and quasi-hydro regimes in magnetic systems is steadily increasing with the advances in fabrication of clean materials, and motivates study of hydrodynamics beyond conventional regimes and probe non-equilibrium transport. We employ the framework of extended irreversible thermodynamics which includes dynamical dissipative currents as quasi-hydro variables, and effect the modified hydrodynamic equations suitable to describe planar Heisenberg ferromagnetic systems in both paramagnetic and ferromagnetic phases. We show that the new transport coefficients and relaxation time scales introduced by quasi-hydro variables can engineer diverse combination of dispersion relations and provide control over the nature of hydrodynamic modes. For instance, we can change the diffusive energy mode into propagating one in multiple ways, including by tuning the relaxation time of magnetization current.
Statistical Mechanics (cond-mat.stat-mech), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
13 pages, 8 figures
Vacancy-enhanced Li solid-solution anodes for solid-state batteries: computational screening enabling high critical current density
New Submission | Materials Science (cond-mat.mtrl-sci) | 2026-10-26 20:00 EDT
Arseniy S. Burov, Nadezhda A. Ashikhmina, Nurlan Zhanabayev, Anton O. Boev, Aleksandra D. Radina, Ilya V. Chepkasov, Alexander G. Kvashnin, Dmitry A. Aksyonov
Sluggish vacancy-mediated self-diffusion in lithium metal limits the critical current density (CCD) of Li anodes in solid-state batteries by promoting interfacial void formation during stripping. To enhance the effective vacancy concentration while preserving the bcc Li host, we screen 50 substitutional solutes using density functional theory (DFT) within a funnel based on automatic phase diagram construction, solution energies, solute-vacancy binding energies, and experimental solubility limits. Using an adaptation of the Lomer model for the dilute limit, we show that only Ag, Ge, and Cd solid solutions are predicted to reach $ 1\mathrm{mAcm^{-2}}$ within their solubility limits. The thermodynamically estimated CCD of Ag at $ \sim 9$ at.% reaches $ \sim 4\mathrm{mAcm^{-2}}$ at a theoretical capacity of $ 1522\mathrm{mAhg^{-1}}$ . Migration barrier calculations indicate that the enhancement may be partially offset by vacancy trapping, necessitating further validation via molecular dynamics simulations. Notably, Hume-Rothery rules alone prove insufficient as prefilters, whereas machine-learning models trained on the DFT data can eliminate most unsuitable solutes early in the funnel and extend the workflow to related solid-solution searches.
Materials Science (cond-mat.mtrl-sci)
Robustness of Skyrmion-Mediated Magnetization Switching in Perpendicular Magnetic Tunnel Junctions (p-MTJs) to Material Disorder and Elevated Temperature
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2026-10-26 20:00 EDT
Prosenjit Das, Md Mahadi Rajib, Jayasimha Atulasimha
Transient-skyrmion mediated voltage-controlled magnetic anisotropy (VCMA) switching is a fast and energy efficient way to magnetization reversal, but its reliability under realistic material disorder and thermal fluctuations remain unclear. In this work, we use stochastic micromagnetic simulations of a 100 nm perpendicular magnetic tunnel junction to study switching reliability under grain-scale variations in Dzyaloshinskii-Moriya interaction, perpendicular magnetic anisotropy, easy-axis orientation, and intergrain exchange coupling. We find that switching remains robust under moderate disorder, with 100% switching observed in 10^4 stochastic simulations after pulse width optimization at both 300 K and 350 K. Increasing the temperature from 300 to 350 K shifts the optimum VCMA pulse width from ~475 to ~450 ps, indicating that an apparent reduction in switching probability at a fixed pulse duration can be primarily due to pulse detuning. In contrast, strong easy-axis disorder reduces the maximum switching probability even after pulse-width optimization, indicating degradation of the switching dynamics. We further show that, under strong easy-axis disorder a transient skyrmion still forms while the subsequent post-pulse dynamics fails to complete the magnetization reversal. Our study therefore establishes the distinction between recoverable reliability due to timing shifts and permanent disorder-induced degradation that simply cannot be recovered by pulse re-tuning. Finally, for no disorders but at room temperature, 100% switching is observed with 10^6 stochastic simulations with correct pulse shaping.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
14 pages, 5 figures
Research Square
Quantum Entanglement Optimization and Prototype
Design in Positronic Simulation Frameworks
Physical Sciences - Article | Atomistic models | 2026-10-25 20:00 EDT
Bulent OZTURK
We present a simulation-driven framework for optimizing quantum entanglement in engineered positronic substrates. Using high-resolution parameter sweeps of a coupling coefficient g and ensemble time-domain traces, we identify a reproducible global entanglement maximum at g ≈ 32.786 and robust secondary plateau regions near g≈60 and g≈100. We quantify entanglement using concurrence-like measures and present a prototype architecture that implements adaptive feedback to maintain maximal entanglement under dynamic perturbations. The archive includes full simulation code, figure-generation scripts and prototype design notes to enable reproducible experimental follow-up.
Research Square:rs-11471731 (2026)
Posted on Research Square
Physical sciences/Materials science/Theory and computation/Atomistic models, Physical sciences/Optics and photonics/Optical physics/Quantum optics