Statistical Mechanics · Cross-listed from physics.soc-ph
A Class of Markovian Self-Reinforcing Processes with Power-Law Distributions
Pavlo Bulanchuk, Sue Ann Koay and Sandro Romani
Solar flares, email exchanges, and many natural or social systems exhibit bursty dynamics, with periods of intense activity separated by long inactivity. These patterns often follow power- law distributions in inter-event intervals or event rates. Existing models typically capture only one of these features and rely on non-local
memory, which complicates analysis and mechanistic interpretation. We introduce a novel self-reinforcing point process whose event rates are governed by local, Markovian nonlinear dynamics and post-event resets. The model generates power-law tails for both inter-event intervals and event rates over a broad range of exponents observed empirically across natural and human phenomena. Compared to non-local models such as Hawkes processes, our approach is mechanistically simpler, highly analytically tractable, and also easier to simulate. We provide methods for model fitting and validation, establishing this framework as a versatile foundation for the study of bursty phenomena.
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Materials Science
Decoding optoelectronic behavior in X$_3$BI$_3$ antiperovskite derivatives through many-body perturbation theory
Ayan Chakravorty, Surajit Adhikari and Priya Johari
Antiperovskite derivatives have emerged as promising candidates for optoelectronic applications. However, due to the significant computational cost, their excitonic and polaronic properties remain underexplored despite being critical for optoelectronic performance. Here, we present the structural, electronic, optical, excitonic, and polaronic properties of a series of antiperovskite derivatives with the chemical formula X$_{3}$BI$_{3}$ (X = Ca, Sr; B = P, As, Sb, Bi) using state-of-the-art first-principles calculations. All the compounds exhibit direct bandgaps with G$_{0}$W$_{0}$@PBE bandgap ranging from 2.42 to 3.02 eV, optimal for efficient light absorption with minimal energy loss.
Exciton binding energies (0.258-0.318 eV) indicate moderate Coulomb attraction, favoring
exciton dissociation. Employing the Feynman polaron model, we established the polaronic properties, where weak to intermediate carrier-
phonon coupling was observed, with polaron mobilities reaching values up to 37.19 cm$^{2}$V$^{-1}$s$^{-1}$. These properties establish X$_{3}$BI$_{3}$ materials as viable candidates for next-generation optoelectronic devices.
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Statistical Mechanics
Loop Charges and Fragmentation in Pairwise Difference Conserving Circuits
Pavel Orlov, Cheryne Jonay and Tomaž Prosen
In this work, we introduce a broad class of
circuits, or
quantum cellular automata, which we call 'pairwise-difference-conserving
circuits' (PDC). These models are characterized by local gates that preserve the pairwise difference of local operators (e.g. particle number). Such
circuits can be de- fined on arbitrary graphs in arbitrary dimensions for both
quantum and classical degrees of freedom. A key consequence of the PDC construction is the emergence of an extensive set of loop charges associated with closed walks of even length on the graph. These charges exhibit a one-dimensional character reminiscent of 1-form
symmetries and lead to strong
Hilbert-space fragmentation. As a case study, we analyze a quasi one-dimensional ladder geometry, where we characterize all dynam- ically disconnected sectors by the loop-charge
symmetries, providing a complete decomposition of the
Hilbert space. For the ladder geometry, we observe clear signatures of nonergodic dynamics even within the largest
symmetry sector.
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Mesoscale and Nanoscale Physics
Magnon scattering and transduction in Coulomb-coupled quantum Hall ferromagnets
Alexander Canright, Deepak Iyer and Matthew S. Foster
The magnetization field of a
quantum Hall ferromagnet (QHFM) can host a variety of
spin textures, including skyrmions and
magnons. When projected into the lowest Landau level with $\nu = 1$ filling, the topological (Pontryagin) charge density of the magnetization field is proportional to the electric charge density, allowing for long-range
spin-
spin interactions. Inspired by recent experimental developments that enable all-electrical generation and detection of
magnons, in this work we theoretically demonstrate two phenomena that can occur due to Coulomb interactions that are unique to QHFMs:
magnons can scatter off of point charges at a distance, and skyrmions can act as transmitters and receivers for
magnons to be transduced between separate layers of a
bilayer QHFM. The latter Coulomb-mediated
spin drag effect occurs at arbitrary distance and could facilitate long-range magnonics, such as detection of
spin waves for future experiments in 2D materials.
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Strongly Correlated Electrons
Generating ferro-spinetic polarizations in altermagnetic insulators
Toshihiro Sato, Mengli Hu, Ion Cosma Fulga et al. (+5 more)
Altermagnets are a novel class of fully
spin-compensated
magnetic materials that nevertheless have
spin-split electronic bands, offering novel perspectives for spintronics applications. Based on a rigorous analysis of altermagnetic many-body models and their
symmetry we establish the important role of two fundamental types of polarizations in altermagnetic
insulators: the charge and the spinetic one, where the latter corresponds to a macroscopic
spin-displacement field. First principles calculations confirm and quantify their presence in real materials. The two polarizations are directly coupled and emerge in orthogonal directions when inversion
symmetry is broken, either by the system developing a spontaneously ferroelectric polarization (in ferroelectric altermagnets), or by a charge displacement induced by an external electric field (for inversion invariant altermagnetic
insulators). This presence of large and switchable
spin accumulations constitute an attractive fundamental feature of altermagnetic
insulators.
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All authors Toshihiro Sato, Mengli Hu, Ion Cosma Fulga, Oleg Janson, Jorge I. Facio, Alessandro Stroppa, Fakher F. Assaad, Jeroen van den Brink
Superconductivity
Helical phases and Bogoliubov Fermi surfaces probed by superconducting diode effects
Zekun Zhuang, Daniel Shaffer, Jaglul Hasan et al. (+1 more)
Noncentrosymmetric
superconductors (NCSs) with Rashba
spin-orbit coupling (SOC) and in-plane
magnetic fields have emerged as natural platforms for realizing both the bulk superconducting diode effect (SDE) and the Josephson diode effect (JDE) - phenomena characterized by unequal critical currents in opposite directions due to the simultaneous breaking of time-reversal and inversion
symmetries. Using the quasiclassical Eilenberger formalism, we systematically investigate both the bulk SDE and the JDE in a clean NCS with Rashba SOC and in-plane
magnetic fields. For the bulk system, we find that the diode efficiency can nominally approach its maximal value at the critical endpoint of the first-order Lifshitz transition between weak and strong helical phases featuring finite-momentum Cooper pairs, the latter marked by the emergence of Bogolyubov
Fermi surfaces (BFSs). In a Josephson junction, we show that finite-momentum pairing in the superconducting leads is the dominant mechanism behind the JDE in short junctions, whereas in long junctions it is primarily governed by the Zeeman field in the normal region. In the long-junction regime, the diode efficiency additionally oscillates between positive and negative values as a function of
magnetic field at low fields, providing a route toward a highly tunable Josephson diode. At higher fields, the onset of BFSs in the strong helical phase leads to a sharp suppression of both the JDE and the Josephson current when the current direction is aligned with momenta along the BFS, resulting in strong anisotropy. We propose that this anisotropy in the Josephson current offers an alternative method for detecting BFSs, applicable to systems with or without a JDE.
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All authors Zekun Zhuang, Daniel Shaffer, Jaglul Hasan, Alex Levchenko
Strongly Correlated Electrons
Haerter-Shastry kinetic magnetism and metallicity in the triangular Hubbard model
Sogoud Sherif, Prakash Sharma, Aman Kumar et al. (+1 more)
The fermionic Hubbard model, when combined with frustration, associated with the breaking of particle-hole
symmetry, harbors a rich phase diagram. Theoretical findings associated with the nature of magnetism and
metallicity across this phase diagram are now being actively investigated in triangular Hubbard cold atom and solid-state (moiré) based emulators. Building on the theoretical work of Haerter and Shastry, we explore the impact of kinetically frustrated magnetism, a phenomenon where
antiferromagnetic order emerges without any underlying
magnetic interactions, at finite hole density. We numerically study the infinite-$U$ triangular Hubbard model using the density
matrix renormalization group
algorithm and estimate the stability of the kinetically induced $120^{\circ}$
antiferromagnetic state to hole doping. Beyond the Haerter-Shastry regime, we find an intermediate phase with multimer (involving multiple correlated
spins) stripes that eventually gives way to a paramagnet. We also find evidence of gapless charge excitations (
metallicity) throughout the phase diagram for finite hole density. We discuss the implications at large, but finite, values of $U/t$, and investigate whether kinetic magnetism and superexchange collaborate or compete.
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All authors Sogoud Sherif, Prakash Sharma, Aman Kumar, Hitesh J. Changlani
Strongly Correlated Electrons · Cross-listed from hep-th
Lieb-Robinson causality and non-Fermi liquids
Subham Dutta Chowdhury, Sean A. Hartnoll and Aditya Hebbar
Quantum mechanical
lattice models with local, bounded interactions obey Lieb-Robinson causality. We show that this implies a domain of analyticity of the retarded Green's function $G^R(\omega,{\bf k})$ of local
lattice operators as a function of complex frequency $\omega$ and momentum ${\bf k}$, similar to the lightcone analyticity property of relativistic field theories. Low-energy effective descriptions of the dynamics must be consistent with this microscopic analyticity constraint. We consider two canonical low-energy fermionic Green's functions describing non-
Fermi liquids, the marginal
Fermi liquid and the `Hertz
liquid'. The pole in these Green's functions must be outside of the Lieb-Robinson domain of analyticity for all complex momenta captured by the low-energy theory. We show that this constraint upper bounds the magnitude of the dimensionless non-
Fermi liquid coupling in certain Hertz
liquids. We furthermore obtain, from causality, an upper bound on the magnitude $|G^R(\omega,{\bf k})|$ within the analytic domain. We use this bound to constrain the quasiparticle residue of the non-
Fermi liquids.
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Statistical Mechanics
Revisiting entropies: formal properties and connections between Boltzmann-Gibbs, Tsallis and Rényi
Kelvin dos Santos Alves and Rogerio Teixeira Cavalcanti
The aim of the present paper is to present a careful and accessible discussion of the formal aspects of Boltzmann-Gibbs and Tsallis
entropies. We begin with a brief overview of Boltzmann-Gibbs
entropy, highlighting its main properties and the uniqueness
theorems formulated by Shannon and Khinchin. Once these foundational results are established, we introduce the framework of nonadditive statistical mechanics, defining Tsallis
entropy, discussing its properties and uniqueness
theorem, and contrasting it with the results from additive statistical mechanics. We also show that, in an appropriate limit, the Boltzmann-Gibbs results are recovered. The article concludes with a brief discussion of Rényi
entropy and its connections to the previously defined entropic forms.
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Strongly Correlated Electrons
Instabilities of a Generalized Gross-Neveu Quantum Criticality
Jaewon Kim
We study the instabilities to the conformal critical point of an exactly solvable family of Gross-Neveu models. Using conformal field theory techniques, we construct the zero-temperature phase diagram and identify the superconducting and charge neutral ordered phases that destabilize the critical point. Both instabilities appear only when the
fermions are strongly renormalized, above a critical anomalous dimension. A higher
fermion anomalous dimension also raises the critical degree of time-reversal-
symmetry breaking required to suppress superconductivity, indicating that pairing becomes more robust with stronger renormalization.
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Materials Science
An Encoder-Decoder Foundation Chemical Language Model for Generative Polymer Design
Harikrishna Sahu, Wei Xiong, Anagha Savit et al. (+2 more)
Traditional machine learning has advanced
polymer discovery, yet direct generation of chemically valid and synthesizable
polymers without exhaustive enumeration remains a challenge. Here we present polyT5, an encoder-decoder chemical
language model based on the T5 architecture, trained to understand and generate
polymer structures. polyT5 enables both property prediction and the targeted generation of
polymers conditioned on desired property values. We demonstrate its utility for dielectric
polymer design, seeking candidates with dielectric constant >3, bandgap >4 eV, and glass transition temperature >400 K, alongside melt-processability and solubility requirements. From over 20,000 generated promising candidates, one was experimentally synthesized and validated, showing strong agreement with predictions. To further enhance usability, we integrated polyT5 within an agentic AI framework that couples it with a general-purpose LLM, allowing natural
language interaction for property prediction and generative design. Together, these advances establish a versatile and accessible framework for accelerated
polymer discovery.
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All authors Harikrishna Sahu, Wei Xiong, Anagha Savit, Shivank S Shukla, Rampi Ramprasad
Strongly Correlated Electrons
Vector spin polarization evolution determined in an entangled muon-fluorine system under pulsed excitation
Dipranjan Chatterjee, Benjamin M. Huddart, Hank C. H. Wu et al. (+4 more)
A
spin-polarized
muon implanted into a fluoride forms a coupled F–$\mu$–F complex in which the
muon spin and neighbouring fluorine
nuclear spins become entangled. Here we apply
radio-frequency (RF) excitation to this coupled system and use the three-dimensional distribution of emitted positrons to reconstruct the time-dependent
evolution of the
muon spin polarization. This three-dimensional readout, using single
spin detection, is not possible in a single NMR experiment and demonstrates significant advantages that are achieved by using RF
muon techniques. We demonstrate the application of this vector-readout method to the experimental observation of a
muon spin echo signal that is controlled by the dipolar coupling to fluorine, as well as to a double resonance experiment, in which we use pulses tuned to separate frequencies to address both the
muon and fluorine
spins. This targeted approach, in which selective RF pulses can control the
muon spin and other
spins to which it is coupled, provides a novel route for probing systems of entangled
spins.
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All authors Dipranjan Chatterjee, Benjamin M. Huddart, Hank C. H. Wu, Dharmalingam Prabhakaran, Alex Louat, Stephen P. Cottrell, Stephen J. Blundell
Strongly Correlated Electrons · Cross-listed from hep-th
Sharp Transitions for Subsystem Complexity
Yale Fan, Nicholas Hunter-Jones, Andreas Karch et al. (+1 more)
The
circuit complexity of time-evolved pure
quantum states grows linearly in time for an exponentially long time. This behavior has been proven in certain models, is conjectured to hold for generic
quantum many-body systems, and is believed to be dual to the long-time growth of black hole interiors in AdS/CFT. Achieving a similar understanding for mixed states remains an important problem. In this work, we study the
circuit complexity of time-evolved subsystems of pure
quantum states. We find that for greater-than-half subsystem sizes, the complexity grows linearly in time for an exponentially long time, similarly to that of the full state. However, for less-than-half subsystem sizes, the complexity rises and then falls, returning to low complexity as the subsystem equilibrates. Notably, the transition between these two regimes occurs sharply at half system size. We use
holographic duality to map out this picture of subsystem complexity dynamics and rigorously prove the existence of the sharp transition in random
quantum circuits. Furthermore, we use holography to predict features of complexity growth at finite temperature that lie beyond the reach of techniques based on random
quantum circuits. In particular, at finite temperature, we argue for an additional sharp transition at a critical less-than-half subsystem size. Below this critical value, the subsystem complexity saturates nearly instantaneously rather than exhibiting a rise and fall. This novel phenomenon, as well as an analogous transition above half system size, provides a target for future studies based on rigorous methods.
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All authors Yale Fan, Nicholas Hunter-Jones, Andreas Karch, Shivan Mittal
Materials Science
Scale-bridging dislocation plasticity in MgO at room temperature
Jiawen Zhang, Zhangtao Li, Yuwei Zhang et al. (+7 more)
Dislocations in ceramics have recently gained renewed research interest, in contrast to the traditional belief that ceramics are inherently brittle. Understanding dislocation mechanics in representative
oxides is beneficial for effective dislocation engineering. Here, we use MgO single
crystals with mechanically seeded dislocation densities from about 10 to the power of 12 to about 10 to the power of 15 per square meter to investigate the mechanical behavior such as yield and fracture. Micro-pillar compression tests reveal a dislocation density dependent yield strength, mediated by the varying dominating dislocation mechanisms from nucleation to multiplication/motion. In situ TEM compression measurements highlight the dislocation-seeded samples can achieve a much-improved compressive plastic strain beyond about 70%, with a high yield strength of about 2.35 GPa (diameter of about 400 nm), indicating size effect. Complementary bulk compression tests, along with digital image correlation (DIC), demonstrate a consistent dislocation-mediated deformation and a notable size effect, with bulk samples exhibiting much reduced yield strength (about 120 MPa) compared to the nano-/micro-pillars. Using three-dimensional Discrete Dislocation Dynamics (3D-DDD) simulation, we further qualitatively analyze the collective dislocation activities (slip events) and work hardening during compression. This study provides new insights into dislocation-mediated plasticity in MgO, across different length scales, by systematically tuning dislocation density.
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All authors Jiawen Zhang, Zhangtao Li, Yuwei Zhang, Hendrik Holz, James P. Best, Oliver Preuß, Zhenyong Chen, Yinan Cui, Xufei Fang, Wenjun Lu
Mesoscale and Nanoscale Physics
Fermi arcs for generic nodal points hosting monopoles or dipoles
Ipsita Mandal
Surface-localised states in the form of
Fermi arcs emerge at the interfaces between three-dimensional topological semimetals and their surrounding
vacuum, serving as primary signatures of momentum-space
topology accessible to modern spectroscopic methods. These arcs encode information about topological singularities — nodal points where multiple bands converge — through their
geometric properties. Specifically, the arcs terminate tangentially at the edges of
Fermi-surface projections, delineating where surface modes transition into bulk extended states. The arcs' multiplicity at each node corresponds directly to the underlying topological charge (Berry-
curvature monopole magnitude), thereby offering a window into momentum-space invariants via angle-resolved photoemission experiments. This work establishes a systematic framework for computing surface state configurations applicable to arbitrary nodal degeneracies and band dispersions: (1) nodes with twofold through multifold band multiplicities; and (2) bands exhibiting diverse momentum-dependence patterns, including linear, nonlinear, isotropic, and anisotropic regimes. We additionally examine topologically distinct nodal types where monopole charges vanish but dipolar Berry-
curvature distributions appear, clarifying the surface-state landscape in such unconventional scenarios.
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Mesoscale and Nanoscale Physics
Self-Consistent Model for Gate Control of Narrow-, Broken-, and Inverted-Gap (Topological) Heterostructures
Maximilian Hofer, Christopher Fuchs, Moritz Siebert et al. (+8 more)
Even small electrostatic potentials can dramatically influence the band structure of narrow-, broken-, and inverted-gap materials. A quantitative understanding often necessitates a self-consistent Hartree approach. The valence and conduction band states strongly hybridize and/or cross in these systems. This makes distinguishing between electrons and holes impossible and the assumption of a flat charge carrier distribution at the charge neutrality point hard to justify. Consequently the wide-gap approach often fails in these systems. An alternative is the full-band envelope-function approach by Andlauer and Vogl, which has been implemented into the open-source software package kdotpy (arXiv:2407.12651). We show that this approach and implementation gives numerically stable and quantitatively accurate results where the conventional method fails by modeling the experimental subband density
evolution with top-gate voltage in thick (26 nm - 110 nm), topologically inverted HgTe
quantum wells. We expect our openly-available implementation to greatly benefit the investigation of narrow-, broken-, and inverted-gap materials.
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All authors Maximilian Hofer, Christopher Fuchs, Moritz Siebert, Christian Berger, Lena Fürst, Martin Stehno, Steffen Schreyeck, Hartmut Buhmann, Tobias Kießling, Wouter Beugeling, Laurens W. Molenkamp
Soft Condensed Matter · Cross-listed from q-bio.CB
Mechanical activity enables patterning and discrimination at the immune synapse
Tony Wong, Tom Chou, Suraj Shankar et al. (+1 more)
Immune
cells recognize and discriminate antigens through immunological synapses - dynamic intercellular junctions exhibiting highly organized receptor-ligand patterns. While much work has focused on molecular kinetics and passive mechanisms of pattern formation, the role of active mechanical control in patterning and discrimination remains underexplored. We develop a minimal continuum model coupling receptor binding kinetics, membrane deformation, and cytoskeletal forces, with elastohydrodynamic flow in the synaptic cleft. Numerical simulations and scaling analysis reveal that contractile cortical flows arrest coarsening and stabilize long-lived multifocal clusters, whereas active pulling accelerates cluster dissolution and elevates background receptor binding. Nonequilibrium mechanical forces enable adaptive control over the speed, sensitivity, and dynamic range of affinity discrimination in a pattern-dependent manner. Our results highlight how immune
cells exploit cytoskeletal remodeling to robustly regulate antigen recognition through synaptic patterning.
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All authors Tony Wong, Tom Chou, Suraj Shankar, Shenshen Wang
Materials Science
Interplay of Magnetism, Band Gap Tuning, Optical, and Thermoelectric Responses in Fe-Doped YMnO$_3$: Insights from First-Principles Calculations
Kazi Mazba Kamal and Alamgir Kabir
The hexagonal multiferroic
oxide YMnO$_3$ has demonstrated applications in various fields and is widely researched due to its interesting properties. Since Mn(3d)–O(2p) interactions predominate close to the
Fermi level, doping in the B-site (Mn) with Fe provides a way to modulate the band gap and
magnetic order of YMnO$_3$. The need for a lead-free ferroelectric material with a narrow band gap is crucial for absorbing a wide range of the
solar spectrum. Density functional theory calculations were carried out using GGA and meta-GGA (for an accurate description of the band gap) exchange correlation functional for the Fe-doped YMnO$_3$ multiferroics. Various
magnetic configurations were analyzed, finding collinear G-type AFM as the least energy state. The hexagonal
lattice is retained after Fe doping with slight distortions and a change in
lattice constants. Fe doping reduces
spin frustration and induces magnetization, while reducing the band gap from 1.88 eV for pure to 1.19 eV for a 25 percent doping concentration. Additionally, Fe doping exhibits an enhanced dielectric response, characterized by an increase in the static dielectric constant and the presence of strong absorption peaks in the visible and UV energy ranges. Thermoelectric studies illustrate enhanced conductivity due to increased charge carriers induced by doping. In summary, first-principles predictions of structural, electronic, optical, and transport behavior in Fe-doped YMnO$_3$ provide a foundation for tailoring this
oxide in photovoltaic, thermoelectric, and optoelectronic applications.
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Soft Condensed Matter
Flat quasicrystalline tilings in terms of density wave approach
Aleksey S. Roshal, Olga V. Konevtsova and Sergei B. Rochal
Classical Landau theory considers structural phase transitions and crystallization as a condensation of several critical density waves whose wave vectors are symmetrically equivalent. Analyzing the simplest nonequilibrium Landau potentials obtained for decagonal and dodecagonal cases, we derive constraints on the phases of the critical waves and deduce two pairs of flat tilings that are the simplest from the viewpoint of our theory. Each pair corresponds to the same irreducible interference pattern: the vertices of the first and second tilings are located at its minima and maxima, respectively. The first decagonal pair consists of the Penrose P1 tiling and the Tie and Navette one. The second pair is represented by dodecagonal tiling of squares, triangles, and shields, and previously unidentified one formed by regular dodecagons and identical deformed pentagons. Surprisingly, the proposed method for finding extrema of interference patterns provides a straightforward way to generate the Penrose tiling P3 and its more complicated analogues with 2n-fold
symmetries. Within Landau theory, we discuss the assembly of the square-triangular tiling and its relationship with the dodecagonal tiling that includes shields. Then we develop a nonequilibrium assembly approach that is based on Landau theory and allows us to produce tilings with random phason strain characteristic of quasicrystals. Interestingly, the approach can generate tilings without or with a minimum number of defective tiles. Examples of real systems rationalized within Landau theory are considered as well. Finally, the derivation of other tilings arising from the reducible interference patterns is discussed, and the relative complexity of non-phenomenological interactions required for the assembly of decagonal and dodecagonal structures is analyzed.
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Mesoscale and Nanoscale Physics
Extinction Coefficients of CdSe, CdS, and CdTe Nanoplatelets in Solution: A Practical Tool for Concentration Determination
Michael H. Stewart, Michael W. Swift, Farwa Awan et al. (+6 more)
Semiconductor nanoplatelets possess exceptional optical properties that make them promising candidates for next-generation optoelectronic applications. However, unlike
quantum dots where absorption spectroscopy alone can determine both size and concentration, nanoplatelets present a significant characterization challenge: the absorption peak position reveals only thickness, providing no information about lateral dimensions or concentration. This limitation forces researchers to rely on time-consuming and costly elemental analysis techniques for complete sample characterization. Here, we present an experimentally verified theoretical framework that predicts the frequency-dependent absorption coefficient of randomly oriented CdSe, CdS, and CdTe nanoplatelets, enabling concentration determination from absorption measurements and lateral size estimates. Our model shows that the integrated absorption coefficient depends universally on nanoplatelet surface area and thickness, yielding a practical tool to extract concentrations without laborious elemental analysis. This approach bridges the characterization gap between
quantum dots and nanoplatelets, offering a streamlined method for rapid sample analysis that could accelerate nanoplatelet research and applications.
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All authors Michael H. Stewart, Michael W. Swift, Farwa Awan, Liam Burke, Christopher M. Green, Barbara A. Marcheschi, Igor L. Medintz, Todd D. Krauss, Alexander L. Efros
Superconductivity
Tuning Superconductivity in Sputtered W0.75Re0.25 Thin Films
F. Colangelo, F. Avitabile, Z. Makhdoumi Kakhaki et al. (+7 more)
W0.75Re0.25, in its bulk form, has been shown to be an interesting superconducting material due to its multiple crystalline phases, each exhibiting distinct superconducting characteristics. However, little is known about how these phases manifest in thin-film form, where deposition conditions and dimensionality are critical aspects. Here, we investigate superconducting W0.75Re0.25 thin films deposited via UHV dc magnetron sputtering. In order to tune the crystalline phase of the films, we further explored the effect of incorporating N2 during the deposition. The superconducting and normal-state properties as a function of deposition conditions were investigated, revealing the role of the
crystal phase on the film transport properties.
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All authors F. Colangelo, F. Avitabile, Z. Makhdoumi Kakhaki, A. Kumar, A. Di Bernardo, C. Bernini, A. Martinelli, A. Nigro, C. Cirillo, C. Attanasio
Mesoscale and Nanoscale Physics
Geometric control of the moire twist angle in heterobilayer flakes
Prathap Kumar Jharapla, Nicolas Leconte, Zhiren He et al. (+2 more)
We demonstrate a finite twist-angle stabilization mechanism in
lattice-mismatched 2D heterobilayers, which results from the
geometric alignment between the flake edges and its moire pattern. Using atomistic simulations of
graphene on hexagonal boron nitride flakes with diameters of up to $\sim 2500$Å, we identify robust metastable angles at $\sim 0.61^\circ$ for armchair and $\sim1.89^\circ$ for zigzag-edged flakes, tunable via in-plane heterostrain. This locking mechanism, which relies on energy barriers that are an order of magnitude larger than those of nearby metastable twist angles, provides a
geometric route to precision twist-angle control of two-dimensional
heterostructures and to understand the self-orientation of macroscopic flakes.
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All authors Prathap Kumar Jharapla, Nicolas Leconte, Zhiren He, Guru Khalsa, Jeil Jung
Strongly Correlated Electrons
Modulated symmetries from generalized Lieb-Schultz-Mattis anomalies
Hiromi Ebisu, Bo Han and Weiguang Cao
Symmetries rigidly delimit the landscape of
quantum matter. Recently uncovered spatially modulated
symmetries, whose actions vary with position, enable excitations with restricted mobility, while Lieb-Schultz-Mattis (LSM) type anomalies impose sharp constraints on which
lattice phases are realizable. In one dimensional a
spin chain, gauging procedures have linked modulated
symmetry to LSM type anomaly, but a general understanding beyond 1D remains incomplete. We show that spatially modulated
symmetries and their associated dipole
algebras naturally emerge from gauging ordinary
symmetries in the presence of generalized LSM type anomalies. We construct explicit
lattice models in two and three spatial dimensions and develop complementary field theoretic descriptions in arbitrary spatial dimensions that connect LSM anomaly inflow to higher-group
symmetry structures governing the modulated
symmetries. Our results provide a unified, nonperturbative framework that ties together LSM constraints and spatially modulated
symmetries across dimensions.
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Materials Science
Hydrogen redistribution in Zr-base cladding under gradients in temperature and stress
Lars O. Jernkvist and Ali R. Massih
Computational models are used here for simulating
diffusion-controlled redistribution of hydrogen that is picked up by zirconium-base
nuclear fuel cladding during light water reactor operation. Axial localization of hydrogen, leading to localized precipitation of zirconium hydrides at lower-temperature regions near interpellet gaps, is studied with a bespoke model, while radial
diffusion, leading to formation of a densely hydrided rim subjacent to the waterside
oxide layer, is studied with a more general model. The calculated results are compared with experimental observations and similar computational studies reported in the literature. The results underline the importance of hydrogen redistribution with regard to local embrittlement of the cladding tubes.
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Materials Science
Modeling Polaron Excitations and Stabilization Mechanisms in Conjugated Polymers
Vishal Jindal and Scott T. Milner
Charge carriers in organic
semiconductors form polarons, which are self-localized states stabilized by interactions with their environment. Using a dielectric-stabilized tight-binding model parameterized from first-principles calculations, we compute ground and excited polaron states in poly(3-hexylthiophene) (P3HT). Our results quantitatively reproduce key mid-infrared absorption features, notably the chain-length-dependent shift of the intrachain polaron excitation peak (peak B) and its variation between regioregular and regiorandom P3HT. Comparison to an alternative stabilization mechanism based on local ring distortions reveals that dielectric polarization dominates polaron formation, as ring distortions yield insufficient binding and excitation energies inconsistent with experiments. These findings clarify the microscopic origin of polarons in conjugated
polymers and provide a predictive framework linking polaron energetics to spectroscopic observables, advancing the understanding of charge transport in organic
semiconductors.
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Mesoscale and Nanoscale Physics
Cavity modification of magnetoplasmon mode through coupling with intersubband polaritons
Lucy L. Hale, Daniele De Bernardis, Stephan Lempereur et al. (+12 more)
We investigate the coupling of a multi-mode metal-
insulator-metal cavity to a two-dimensional electron gas (2DEG) in a
quantum well in the presence of a strong
magnetic field. The TM cavity mode is strongly hybridized with an intersubband transition of the 2DEG, forming a polaritonic mode in the ultrastrong coupling regime, while the TE mode remains an almost purely cavity mode. The magnetoplasmon excitation emerging from the presence of the
magnetic field couples with both TM and TE modes, exhibiting different coupling strengths and levels of spatial field inhomogeneity. While the strong homogeneity of the bare TE mode gives rise to the standard anticrossing of strong coupling, the inhomogeneous polaritonic TM mode is shown to activate an observable Coulombic effect in the spectral response, often referred to as non-locality. This experiment demonstrates a cavity-induced modification of the 2DEG response and offers a new route to probing the effect of Coulomb interactions in ultrastrongly coupled systems via reshaping of their cavity mode profiles.
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All authors Lucy L. Hale, Daniele De Bernardis, Stephan Lempereur, Lianhe H. Li, A. Giles Davies, Edmund H. Linfield, Trevor Blaikie, Chris Deimert, Zbigniew R. Wasilewski, Iacopo Carusotto, Jean-Michel Manceau, Mathieu Jeannin, Raffaele Colombelli, Jérôme Faist, Giacomo Scalari
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Optimal quantum reservoir learning in proximity to universality
Moein N. Ivaki, Matias Karjula and Tapio Ala-Nissila
The study of the boundary between classically simulable and computationally complex
quantum dynamics is fundamental to understanding which physical resources may enable enhanced information-processing capabilities. We investigate this within the framework of
quantum reservoir computing by introducing a tunable $N$-
qubit random
circuit model, where a fraction $p$ of Clifford gates are probabilistically substituted with nonstabilizing conditional-$\hat{T}$ gates. We establish a direct correspondence between the reservoir's performance on temporal processing tasks and its
entanglement spectrum statistics and long-range nonstabilizer resource content. To assess scalability, we study the scaling of the anti-flatness of states in the large-$N$ limit at a fixed
circuit depth ratio $d/N \sim \mathcal{O}(1)$. This is taken as a witness to concentration of measures, a known impediment to learning in thermalizing systems. We demonstrate that the learnability and scalability of the reservoir can be continuously controlled by the parameter $p$, allowing us to navigate from classically tractable to maximally expressive
quantum dynamics. These architecture-agnostic results provide a general strategy for designing tunable and expressive
quantum reservoirs, highlighting how certain nonclassical properties control average-case intrinsic learnability and functionality.
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Materials Science
Dislocation-point defect interaction on plasticity across the length scale in SrTiO3
Chukwudalu Okafor, Kohei Takahara, Svetlana Korneychuk et al. (+7 more)
Point defect engineering is widely used to tailor the electronic and transport properties of complex
oxides, yet its influence on dislocation plasticity remains poorly understood. Here, we establish how donor (Nb) doping modifies dislocation nucleation, multiplication, and mobility in single-
crystal SrTiO3 by bridging nano-, meso-, and macroscale deformation. Using a combinatorial approach involving nanoindentation, cyclic Brinell indentation, and bulk uniaxial compression, we show that 0.5 wt% Nb doping consistently suppresses room-temperature plasticity. Nanoindentation reveals increased pop-in stresses, increased
lattice friction stress, and reduced creep rates, indicating inhibited dislocation nucleation and motion with Nb doping. Mesoscale Brinell indentation exhibits discrete, widely spaced slip traces reflecting more difficult dislocation multiplication. Bulk uniaxial compression confirms ~50% higher yield stress in Nb-doped (0.5 wt%) SrTiO3 samples. Comparison with Fe-doped SrTiO3 (equivalent doping concentration) isolates the role of defect chemistry: oxygen vacancies promote incipient plasticity, whereas Sr vacancies dominate in Nb-doped SrTiO3, strongly hindering dislocation motion. This length-scale bridging approach consistently reveals suppressed dislocation nucleation, multiplication, and motion in the 0.5 wt% Nb-doped samples. These insights underline the importance of dislocation-defect chemistry on the mechanical behavior of functional
oxides.
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All authors Chukwudalu Okafor, Kohei Takahara, Svetlana Korneychuk, Isabel Huck, Sebastian Bruns, Ruoqi Li, Yan Li, Karsten Durst, Atsutomo Nakamura, Xufei Fang
Mesoscale and Nanoscale Physics
Netta Karjalainen, Greta Lupi, Rouven Koch et al. (+2 more)
Nanoscale engineered
spin systems, ranging from
spins on surfaces to nanographenes, provide flexible platforms to realize entangled
quantum magnets from a bottom-up approach. However, assessing the
quantum many-body
Hamiltonian realized in a specific experiment remains an exceptional open challenge, due to the difficulty of disentangling competing terms accounting for the many-body excitations. Here, we demonstrate a machine learning strategy to learn a
quantum many-body
spin Hamiltonian from scanning spectroscopy measurements of
spin excitations. Our methodology leverages the spatially resolved reconstruction of the many-body excitations induced by depositing
quantum impurities next to the
quantum magnet. We demonstrate that our
algorithm allows us to predict long-range Heisenberg exchange interactions, anisotropic exchange, and antisymmetric Dzyaloshinskii-Moriya interaction, including in the presence of sizable noise. Our methodology establishes defect-induced spatially resolved dynamical excitations in
quantum magnets as a powerful strategy to understand the nature of
quantum spin many-body models.
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All authors Netta Karjalainen, Greta Lupi, Rouven Koch, Adolfo O. Fumega, Jose L. Lado
Materials Science
First-Principles Investigation of Sr2PrSbO6 Double Perovskite: An Emerging Aspirant for Electrocatalysis, Plasmonic, Photonics, Thermoelectric and Solar Cell Applications
Md. Mohiuddin and Alamgir Kabir
In this study, we investigate the structural properties, chemical stability, and electronic, optical, and thermoelectric properties of $\mathrm{Sr_2PrSbO_6}$ using first-principles calculations based on Density Functional Theory (DFT). The goal of this study is to evaluate its potential contribution to next-generation electrocatalysts, optoelectronic devices, and thermoelectric systems. The structural optimization reveals that $\mathrm{Sr_2PrSbO_6}$ crystallizes in a stable cubic perovskite structure with space group $Fm\bar{3}m$. The calculated formation energy indicates high thermodynamic stability, confirming the viability of $\mathrm{Sr_2PrSbO_6}$ for practical applications. The electronic band structure calculations show that $\mathrm{Sr_2PrSbO_6}$ is a wide bandgap
semiconductor with a direct bandgap of $3.488~\mathrm{eV}$ at the $\Gamma$-point. The calculated density of states (DOS) indicates significant contributions from O $2p$, Sb $5p$, and Pr $5d$ orbitals. Optical property calculations, including the dielectric function and absorption coefficient, reveal strong absorption in the UV regions, making $\mathrm{Sr_2PrSbO_6}$ a promising candidate for optoelectronic applications such as UV light-emitting diodes (LEDs) and photovoltaic-thermoelectric (PV-TE) tandem systems. At room temperature, the calculated dimensionless quantity $ZT$ is $0.33$, which indicates this material as a possible candidate for thermoelectric applications. Our results will serve as a
benchmark for future experimental and theoretical research on the properties of this material.
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