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Physics Condensed Matter

cond-mat Watch Condensed Matter

Friday 19 December

Statistical Mechanics

Quantum quenches across continuous and first-order quantum transitions in one-dimensional quantum Ising models

Andrea Pelissetto, Davide Rossini and Ettore Vicari

We investigate the quantum dynamics generated by quantum quenches (QQs) of the Hamiltonian parameters in many-body systems, focusing on protocols that cross first-order and continuous quantum transitions, both in finite-size systems and in the thermodynamic limit. As a paradigmatic example, we consider the quantum Ising chain in the presence of homogeneous transverse ($g$) and longitudinal ($h$) magnetic fields. This model exhibits a continuous quantum transition (CQT) at $g=g_c$ and $h=0$, and first-order quantum transitions (FOQTs) driven by $h$ along the line $h=0$ ($g<g_c$). In the integrable limit $h=0$, the system can be mapped onto a quadratic fermionic theory; however, any nonvanishing longitudinal field breaks integrability and the spectrum of the resulting Hamiltonian is generally expected to enter a chaotic regime. We analyze QQs in which the longitudinal field is suddenly changed from a negative value $h_i < 0$ to a positive value $h_f>0$. We focus on values of $h_f$ such that the spectrum of the post-QQ Hamiltonian $H(g,h_f)$ lies in the chaotic regime, where thermalization may emerge at asymptotically long times. We study the out-of-equilibrium dynamics for different values of $g$, finding qualitatively distinct behaviors for $g > g_c$ (where the chain is in the disordered phase), for $g = g_c$ (QQ across the CQT), and for $g<g_c$ (QQ across the FOQT line).
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Disordered Systems and Neural Networks · Cross-listed from q-bio.NC

Novel Kuramoto model with inhibition dynamics modeling scale-free avalanches and synchronization in neuronal cultures

Dario Lucente, Letizia Cerutti, Martina Brofiga et al. (+5 more)

Neuronal cultures exhibit a complex activity, bursts, or avalanches, characterized by the coexistence of scale invariance and synchronization, quite stable with the percentage of inhibitory neurons. While this bistable behavior has been already observed in the past, the characterization of the statistical properties of avalanche activity and their temporal organization is still lacking, as well as a model able to reproduce these dynamics. Here, we analyze experimental data of human neuronal cultures with controlled percentage of inhibitory neurons and characterize their statistical properties and dynamical organization. In order to model the experimental data, we propose a novel version of the Kuramoto model for two populations of oscillators, excitatory and inhibitory, implementing successfully the inhibition dynamics. The model can fully reproduce the experimental results, confirming the existence of correlations in the temporal organization of avalanche activity and the presence of an amplification - attenuation regime, as found in the human brain.
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All authors Dario Lucente, Letizia Cerutti, Martina Brofiga, Alessandro Sarracino, Giulia Parodi, Sergio Martinoia, Paolo Massobrio, Lucilla de Arcangelis

Materials Science

Switchable Giant Spin Injection Current in Janus Altermagnet Fe$_2$SSeO

Fanxian Pei, Run-Wu Zhang, Lei Li et al. (+2 more)

Generating and controlling spin current in miniaturized magnetic quantum devices remains a central objective of spintronics, due to its potential to enable future energy-efficient information technologies. Among the existing magnetic phases, altermagnetism have recently emerged as a highly promising platform for spin current generation and control, going beyond ferromagnetism and antiferromagnetism. Here, we propose a symmetry-allowed spin photovoltaic effect in two-dimensional (2D) altermagnetic semiconductors that enables predictable control of giant spin injection currents. Distinct from parity-time ($\mathcal{PT}$)-antiferromagnets, Janus altermagnetic semiconductors generate not only shift current but also a unique injection current with spin momentum locked in a specific direction under linearly polarized light – a mechanism absent in $\mathcal{PT}$-antiferromagnets. Through symmetry analysis and first-principles calculations, we identify Janus Fe$_2$SSeO as a promising candidate. Specifically, the monolayer Fe$_2$SSeO exhibits a polarization-dependent injection conductivity reaching $\sim$1,200~$\mu$A/V$^{2}\!\cdot\!\hbar/2e$, and the giant spin injection current can be effectively switched by rotating the magnetization direction and engineering strains. These findings underscore the potential of 2D altermagnets in spin photovoltaics and open avenues for innovative quantum devices.
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All authors Fanxian Pei, Run-Wu Zhang, Lei Li, Dan Li, Yugui Yao

Materials Science

Spinless electric toroidal multipoles in ferroaxial ${\rm K_2Zr(PO_4)_2}$ revealed by symmetry-adapted closest Wannier analysis

Yu Xie, Rikuto Oiwa and Satoru Hayami

From a symmetry perspective, ferroaxial order belongs to the same symmetry as time-reversal-even pseudovectors. Experimentally, ${\rm K_2Zr(PO_4)_2}$ is known to undergo a displacive-type phase transition from a non-ferroaxial to a ferroaxial phase. To identify the key microscopic ingredients driving this transition, we carry out a quantitative analysis combining density-functional theory calculations and symmetry-adapted closest Wannier analysis. As a result, we show that electric toroidal dipole, electric toroidal octupole, and electric hexadecapole, which belong to the same irreducible representation, make dominant contributions to the ferroaxial transition. In particular, we find that spinless electric toroidal octupoles, which originate from spin-independent off-diagonal real hopping between the $p$ orbitals on P and O atoms and between the $d$ orbitals on Zr atoms and $p$ orbitals on O atoms, provide the most significant contributions. Moreover, we explicitly analyze the orbital characters involved in the relevant hybridizations associated with these multipoles. We further show that the relativistic spin–orbit coupling has a negligible influence on the ferroaxial transition. These results demonstrate that spin-independent orbital hybridization between different orbitals on different atoms plays a crucial role in inducing the ferroaxial transition.
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Materials Science

In-operando dipole orientation for bipolar injection from air-stable electrodes into organic semiconductors

Anton Kirch, Joan Ràfols-Ribé, Kumar Saumya et al. (+9 more)

Efficient charge-carrier injection from air-stable electrodes into organic semiconductors (OSCs) is essential for fabricating solution-processed organic optoelectronic devices under ambient conditions. Today, this is typically achieved by incorporating doped OSC interlayers, introducing self-assembled dipole monolayers, or adding mobile ions to the active material (AM). Here, we demonstrate an alternative approach that eliminates the need for additional injection layers or ionic additives. We achieve this by blending the dipolar compound TMPE-OH into the electroluminescent polymer Super Yellow (SY) and depositing this sole AM between two air-stable electrodes, forming a single-layer, dipole-doped OLED (D-OLED). By tracking its transient voltage-luminance response, performing impedance spectroscopy, and comparing these characteristics with two other single-layer device concepts, i.e. a neat-SY OLED without a dipolar compound and a light-emitting electrochemical cell (LEC) containing mobile ions, we can establish that the auxiliary dipoles in the D-OLED reorient under the applied driving voltage, enabling immediate luminance turn-on and lowering the injection barriers at both electrodes. Finally, we demonstrate that the D-OLED achieves current efficacies comparable to those of SY OLEDs incorporating dedicated injection layers or LECs. Our study establishes dipolar doping as a practical strategy for efficient bipolar charge injection from air-stable electrodes in solution-processed organic semiconductor devices.
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All authors Anton Kirch, Joan Ràfols-Ribé, Kumar Saumya, Thushar Salkod Mahabaleshwar, William Strömberg, Ajay Kumar Poonia, Preetam Dacha, Yuntao Qiu, Sri Harish Kumar Paleti, Christian Larsen, Nicolò Maccaferri, Ludvig Edman

Superconductivity

Probing the intermediate state of type-I superconductor SnAs using Muon Spin Spectroscopy

Shashank Srivastava, Omkar Kulkarni, Arushi et al. (+8 more)

Superconductivity with non-trivial band topology provides a novel platform for exploring topological superconductivity and its quantum applications. A detailed microscopic understanding of the superconducting ground state in such materials is crucial. Here, we report the results of a muon spin rotation/relaxation study ($\mu$SR) of the topologically non-trivial superconductor SnAs, which exhibits superconductivity below 3.74(1) \si{K}. Zero-field (ZF) $\mu$SR data reveal that this system is a time-reversal invariant superconductor, and systematic transverse-field (TF) $\mu$SR measurements unveil the type-I nature of the SnAs superconductor. We have established the superconducting phase diagram to understand the intermediate state of type-I superconductors. Moreover, ab initio band structure and phonon calculations are performed, which correlate with the experimental characterization.
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All authors Shashank Srivastava, Omkar Kulkarni, Arushi, Deepak Singh, Poulami Manna, Priya Mishra, Suhani Sharma, Pabitra Kumar Biswas, Rhea Stewart, Adrian D. Hillier, Ravi Prakash Singh

Materials Science

Deep Learning Enabled Nanoscale X-ray Photoemission Electron Microscopy (nanoXPEEM)

Aashwin Mishra, Daniel Ratner and Quynh Nguyen

Understanding and manipulating two-dimensional materials for real-world applications remains challenging due to a lack of effective and high-throughput characterization techniques. Soft X-ray time-of-flight photoemission electron microscopy (XPEEM) provides element- and depth-sensitive information of materials and buried interfaces. However, chromatic and spherical aberrations cannot be corrected with electron-lens combinations. These aberrations, combined with astigmatism and space-charge effects, significantly degrade the spatial and energy resolutions. To overcome this limitation, we outline a spatial-attention based deep learning approach to automatically correct for these effects and attain nanometer resolution over the entire field-of-view (FoV). The combination of this corrective algorithm with XPEEM, termed as nanoXPEEM, establishes a new record of 48-nm spatial resolution with a 232-micrometer diameter FoV in the soft x-ray regime (700-1000 eV). nanoXPEEM provides unique spatial mapping of the element-specificity, depth-sensitivity, and local structure on the nanoscale. It can bridge the current gap to achieve angstrom (atomic) scale resolution.
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Materials Science

Vector Spin Chirality Switching in Noncollinear Antiferromagnets

Aritra Dey, R. Bhuvaneswari, Sourav Chowdhury et al. (+14 more)

Spin chirality provides a powerful route to control magnetic and topological phases in materials, enabling next-generation spintronic and quantum technologies. Coplanar noncollinear antiferromagnets with Kagome lattice spin geometries host vector spin chirality (VSC), the handedness of spin arrangement, and offer an excellent platform for chirality-driven phase control. However, the microscopic mechanisms governing VSC switching and its coupling to magnetic order, electronic structure, and quantum geometry remain elusive, with experimental evidence still lacking. Here, we present conclusive experimental evidence of temperature-driven VSC switching in an archetypal noncollinear antiferromagnetic manganese chromium nitride (Mn3CrN) epitaxial thin films. The VSC switching induces a concomitant quantum-geometric and Lifshitz transition, manifested through a pronounced peak in anomalous Hall conductivity remanence, a metal-insulator-like crossover in longitudinal resistivity, and a distinct evolution of x-ray magnetic circular dichroic signal. The reversal of VSC reconstructs the spin configuration, Fermi surface topology and Berry curvature, marking a unified magnetic-electronic-quantum geometric transition. This emergent behaviour, captured through magneto-transport and magneto-optic measurements, and supported by first-principles theory establish VSC as an active control knob for chirality-driven phase engineering and the design of multifunctional quantum devices.
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All authors Aritra Dey, R. Bhuvaneswari, Sourav Chowdhury, Souvik Banerjee, Manisha Bansal, Smritiparna Ghosh, Anwesha Bera, Raktim Maity, Jayjit Kumar Dey, Weibin Li, Ashalatha Indiradevi Kamalasanan Pillai, Manuel Valvidares, Subhajit Roychowdhury, Magnus Garbrecht, Tuhin Maity, Umesh Waghmare, Bivas Saha

Materials Science

Enhancing Reconstruction Capability of Wavelet Transform Amorphous Radial Distribution Function via Machine Learning Assisted Parameter Tuning

Deriyan Senjaya and Stephen Ekaputra Limantoro

Understanding atomic structures is crucial, yet amorphous materials remain challenging due to their irregular and non-periodic nature. The Wavelet Transform Radial Distribution Function (WT-RDF) offers a physics-based framework for analyzing amorphous structures, reliably reconstructing the first and second Radial Distribution Function (RDF) peaks and overall curve trends in both binary (Ge 0.25 Se 0.75) and ternary Ag x(Ge 0.25 Se 0.75)100-x (x = 5, 10, 15, 20, 25) systems. Despite these strengths, WT-RDF shows limitations in amplitude accuracy, which affects quantitative analyses such as coordination numbers. The shortcoming arises from improper parameter (a, b, Kf, C, and {\Lambda})) selection, as the parameters intrinsically represent atomic interactions within amorphous materials. This study addresses the issue by optimizing WT-RDF parameters using a machine learning approach via learnable parameter optimization, parameter bounding, and selective loss, producing the enhanced WT-RDF+ framework. WT-RDF+ improves the precision of peak reconstructions and outperforms benchmark Machine Learning (ML) models, including Radial Basis Function (RBF) and Long Short-term Memory (LSTM), when trained on only 25% of the binary dataset. Specifically, the machine learning benchmarks are defined as regressors with radial distance r input and G(r) output taken from Ab Initio Molecular Dynamics (AIMD) RDF simulation, not the reduced structure factor SR(q) to G(r) inversions. These results demonstrate that WT-RDF+ is a robust and reliable model for RDF reconstruction of Ge-Se and Ag-Ge-Se family.
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Soft Condensed Matter

Segregation dynamics in active-passive mixtures of semiflexible filaments

Chitrak Bhowmik, Aparna Baskaran and Sriram Ramaswamy

We study the segregation of motile semiflexible filaments from a background of similar but non-motile filaments. Our Langevin dynamics simulations reveal a wide range of emergent structures governed by filament flexibility and activity, i.e., self-propulsion strength. The system segregates at low activities, while at high activities it undergoes remixing which is a characteristic feature of semi-flexible active filaments. We show that collision-induced softening of single filaments is the dominant mode for this remixing. We provide a scaling argument for the lowering of the active polymer stiffness and show that it agrees well with the lowering of the segregation order parameter. We expect that our studies will shed light on the spatial organization of biofilaments within the cell, on the plasma-membrane, and beyond, and help in the design of novel biomaterials whose structure can be tuned via the properties of the active or the passive filaments.
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Materials Science

Yb 4f-Ta 5d Hybridization and Valence Evolution in Tetragonal Tungsten Bronze Ba(3-x)YbxTa5O15

Daisuke Takegami, Haruki Takei, Masato Yoshimura et al. (+2 more)

Here we investigate the electronic structure of the tetragonal tungsten bronze Ba$_{3-x}$Yb$_x$Ta$_{5}$O$_{15}$ by making use of hard x-ray photoemission spectroscopy. The core level spectroscopy shows that the substitution with Yb ions in the series first occurs on the compact S1 site. For $x\leq1$, Yb is found to be dominantly Yb$^{2+}$ with a small mixing of Yb$^{3+}$, while for $x>1$, a significant increase of Yb$^{3+}$ is found, suggesting not only that site S2 favours Yb$^{3+}$, but also that their presence affects also the valency of the ions in site S1. The valence band spectra shows a relatively deep Yb$^{2+}$ doublet, but at the same time indications of a Ta~$5d$-Yb~$4f$ interaction are found, suggesting the presence of Yb~$4f$ carriers at the Fermi level through this hybridization. Our results thus point towards an exotic form of $d$-$f$ electronic interplay that together with the structural degrees of freedom can result in the unusual trends observed in the physical properties of Ba$_{3-x}$Yb$_x$Ta$_{5}$O$_{15}$.
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All authors Daisuke Takegami, Haruki Takei, Masato Yoshimura, Takuro Katsufuji, Takashi Mizokawa

Disordered Systems and Neural Networks · Cross-listed from q-fin.ST

Modeling financial time series with $\phi^{4}$ quantum field theory

Dimitrios Bachtis, David S. Berman and Arabella Schelpe

We use a $\phi^{4}$ quantum field theory with inhomogeneous couplings and explicit symmetry-breaking to model an ensemble of financial time series from the S$\&$P 500 index. The continuum nature of the $\phi^4$ theory avoids the inaccuracies that occur in Ising-based models which require a discretization of the time series. We demonstrate this using the example of the 2008 global financial crisis. The $\phi^{4}$ quantum field theory is expressive enough to reproduce the higher-order statistics such as the market kurtosis, which can serve as an indicator of possible market shocks. Accurate reproduction of high kurtosis is absent in binarized models. Therefore Ising models, despite being widely employed in econophysics, are incapable of fully representing empirical financial data, a limitation not present in the generalization of the $\phi^{4}$ scalar field theory. We then investigate the scaling properties of the $\phi^{4}$ machine learning algorithm and extract exponents which govern the behavior of the learned couplings (or weights and biases in ML language) in relation to the number of stocks in the model. Finally, we use our model to forecast the price changes of the AAPL, MSFT, and NVDA stocks. We conclude by discussing how the $\phi^{4}$ scalar field theory could be used to build investment strategies and the possible intuitions that the QFT operations of dimensional compactification and renormalization can provide for financial modelling.
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Materials Science

Anomalous Nernst effect in amorphous Tb-Fe-Co thin films

Hiroto Imaeda, Tsunehiro Takeuchi, Hiroyuki Awano et al. (+1 more)

We conducted a comprehensive study on the compositional dependence of the anomalous Nernst effect (ANE) in amorphous (amo.) Tb-Fe-Co thin films. The anomalous Nernst coefficient strongly depends not only on the Tb composition but also on the transition metal composition, reaching a maximum of 1.8 uV/K for amo. Tb11.0(Fe50.0Co50.0) 89.0. By evaluating the electrical and thermoelectric properties, it was clarified that this maximum is achieved by the superposition of two large contributions: S_1 arising from direct transverse electron conduction due to a temperature gradient, and S_2 resulting from the combined Seebeck and anomalous Hall effects. We discovered that the anomalous Nernst conductivity, which is attributed to Berry curvature, varied significantly with the transition metal, even in an amorphous material lacking long-range crystalline order. Our research indicates that it is possible to control the electronic states that influence thermoelectric properties, even in the amorphous state.
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All authors Hiroto Imaeda, Tsunehiro Takeuchi, Hiroyuki Awano, Kenji Tanabe

Quantum Gases · Cross-listed from quant-ph

Emergent Universality Class in Dissipative Quantum Systems with Dipole Moment Conservation

Wenbo Zhou, Yuke Zhang and Pengfei Zhang

Understanding the non-equilibrium dynamics of quantum many-body systems remains one of the grand challenges of modern physics. In particular, increasing attention has been devoted to the emergence of non-equilibrium universality classes that have no equilibrium counterparts. A prominent example is the Kardar-Parisi-Zhang universality class realized in dissipative Bose-Einstein condensates. In this Letter, motivated by recent experimental advances, we investigate the universal dynamics of dissipative quantum systems with dipole moment conservation. We develop an effective field theory description, supported by a concrete quantum spin model, to capture the resulting universal behaviors. Our analysis unveils a novel strongly interacting non-equilibrium fixed point that governs the equal-time phase fluctuations in systems with either strong or weak dipole symmetries. Moreover, charge transport becomes subdiffusive in the presence of strong dipole symmetry, while it remains diffusive in the weakly symmetric case. Our results reveal the intricate interplay between kinetic constraints and dissipation in quantum many-body systems.
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Statistical Mechanics

A symbiotic SIR process

Gerardo Palafox-Castillo, Ericka Fabiola Vázquez-Alcalá and Arturo Berrones-Santos

We study a symmetric two-disease SIR co-infection model on networks in which co-infected individuals recover at a rate distinct from that of single infections. The model explicitly represents all co-infection states and features absorbing recovered compartments for both diseases. Within a mean-field network approximation, we derive the basic reproduction number of the coupled system and show that invasion thresholds coincide with those of two independent SIR processes. Exploiting an exchange symmetry in the equal-transmission regime, we reduce the dynamics to a lower-dimensional invariant subsystem and analyze the impact of the co-infection recovery rate. We prove that slower recovery of co-infected individuals monotonically increases the co-infection burden and yields a lower bound on epidemic duration that grows as the co-infection recovery rate decreases. Numerical simulations further indicate that reduced co-infection recovery can increase the epidemic peak, an effect supported by a sensitivity-equation analysis. Together, these results highlight how co-infection-specific recovery dynamics can substantially alter transient epidemic behavior, even in the absence of endemic equilibria.
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Mesoscale and Nanoscale Physics

Shot noise signatures identifying non-Abelian properties of Jackiw-Rebbi zero modes

Haoran Ge, Zhen Chen, Yijia Wu et al. (+1 more)

Jackiw-Rebbi zero modes were first proposed in 1976 as topologically protected zero-energy states localized at domain walls in one-dimensional Dirac systems. They have attracted widespread attention in the field of topological quantum computing, as they serve as non-superconducting analogs of Majorana zero modes and support non-Abelian statistics in topological insulator systems. %In the braiding process of the Jackiw-Rebbi zero modes, their braiding properties are closely related to the strength of disorder. However, compared to their Majorana cousins, the braiding properties of Jackiw-Rebbi zero modes are vulnerable to the on-site energy deviation between the modes involved in the experiment. In this work, we propose to estimate the braiding properties of Jackiw-Rebbi zero-modes through measurements of transport signatures, which are readily measurable in current experiments. We find that the fidelity of braiding operation reaches unity when the current noise is fully suppressed, while this braiding fidelity monotonously decreases with the increasing of the current noise. Based on these transport signatures, we further discuss the correspondence between Majorana and Jackiw-Rebbi zero modes, highlighting their similarity in supporting non-Abelian statistics.
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All authors Haoran Ge, Zhen Chen, Yijia Wu, X. C. Xie

Soft Condensed Matter

Growth of Dynamic and Static Correlations in the Aging Dynamics of a Glass-Forming Liquid

Santu Nath and Smarajit Karmakar

Using extensive molecular dynamics simulations, we have performed finite-size scaling (FSS) in the aging regime of a model glass-forming liquid to investigate how the length scales associated with amorphous order (static length) and dynamic heterogeneity (dynamic length) evolve with waiting time. The $\alpha$-relaxation time in the aging regime reveals non-monotonic finite-size effects with a peak at an intermediate system size, which, as far as we know, are not found in the equilibrium systems, and the peak position shifts to larger system sizes with decreasing temperature and increasing waiting time, indicating a growth of a characteristic length scale with waiting time. The extracted correlation volume associated with amorphous order increases logarithmically with the waiting time. Detailed analysis of the dependence of the length scale on waiting time allowed us to estimate the static length scale in the deep supercooled liquid regime. The dynamic length scale, obtained from FSS and block analysis of the four-point dynamic susceptibility, follows a power-law growth with waiting time. The values of the length scales obtained agree well with those obtained from different spatial correlation functions.
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Mesoscale and Nanoscale Physics · Cross-listed from math-ph

Harmonic band theory: rigidity of non-zero degree harmonic maps from 2-torus to complex projective space

Yoshinori Hashimoto, Bruno Mera and Tomoki Ozawa

We prove the rigidity of isotropic harmonic maps from a 2-torus to a complex projective space, when they are constructed from holomorphic embeddings associated to complete linear systems. We also prove that this rigidity holds for any holomorphic embeddings without special hyperosculation points, with an extra assumption on the pullbacks of Fubini–Study symplectic forms. These results ensure the rigidity of towers of harmonic bands in condensed matter physics.
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Materials Science · Cross-listed from quant-ph

Evaluating Sample-Based Krylov Quantum Diagonalization for Heisenberg Models with Applications to Materials Science

Roman Firt, Neel Misciasci, Jonathan E. Mueller et al. (+4 more)

We evaluate the Sample-based Krylov Quantum Diagonalization (SKQD) algorithm on one- and two-dimensional Heisenberg models, including strongly correlated regimes in which the ground state is dense. Using problem-informed initial states and magnetization-sector sweeps, SKQD accurately reproduces ground-state energies and field-dependent magnetization across a range of anisotropies. Benchmarks against DMRG and exact diagonalization show consistent qualitative agreement, with accuracy improving systematically in more anisotropic regimes. We further demonstrate SKQD on quantum hardware by implementing 18- and 30-qubit Heisenberg chains, obtaining magnetization curves that match theoretical expectations. Simulations on small 2D square-lattice systems further demonstrate that the method applies effectively beyond 1D geometries.
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All authors Roman Firt, Neel Misciasci, Jonathan E. Mueller, Triet Friedhoff, Chinonso Onah, Aaron Schulze, Sarah Mostame

Thursday 18 December

Materials Science · Cross-listed from cs.DC

Accelerating discovery across scientific disciplines through reproducible workflows with AiiDAlab

Aliaksandr V. Yakutovich, Daniel Hollas, Edan Bainglass et al. (+16 more)

With ever-increasing computational capabilities, robust and automated research workflows have become essential for orchestrating large numbers of interdependent simulations. However, significant technical expertise is still required to configure execution environments, define calculation inputs, interpret outputs, and manage the complexity of parallel code execution on remote machines. To address these challenges, we developed AiiDAlab, a Jupyter-based web platform powered by the AiiDA computational infrastructure that provides a framework for managing and automating computational workflows while ensuring reproducibility through full provenance tracking. Through a collection of open-source user-friendly applications, AiiDAlab enables scientists to set up, execute, and analyze complex computational workflows without interacting directly with the underlying technical details, allowing them to focus on their research questions. In this paper, we discuss how AiiDAlab has matured over the past few years, expanding beyond computational materials science and its AiiDA origins. We present recent developments towards integrating with electronic laboratory notebooks (ELNs) for FAIR-compliant data management, adoption in large-scale facilities for secure access to experimental data and analytical tools, and applications in educational settings. Together with community-driven efforts to simplify onboarding, improve access to computational resources, and support large-scale data workflows, these advancements position AiiDAlab as a powerful platform for accelerating scientific discovery and fostering collaboration across disciplines.
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All authors Aliaksandr V. Yakutovich, Daniel Hollas, Edan Bainglass, Jusong Yu, Corsin Battaglia, Miki Bonacci, Lucas Fernandez Vilanova, Stephan Henne, Anders Kaestner, Michel Kenzelmann, Graham Kimbell, Jakob Lass, Fabio Lopes, Daniel G. Mazzone, Andres Ortega-Guerrero, Xing Wang, Nicola Marzari, Carlo A. Pignedoli, Giovanni Pizzi

Soft Condensed Matter

The extraordinary importance of self-avoiding behavior in two-dimensional polymers: Insights from large-deviation theory

Eleftherios Mainas, Jan Tobochnik and Richard Stratt

Some recent work pointed out the usefulness of taking a large-deviation perspective when trying to extract anything resembling a macroscopic order parameter from a computer simulation. In this paper we note that the end-to-end distance of polymers is such an order parameter. The presence of long-ranged excluded volume interactions leads to significant qualitative differences between the conformations of two- and three-dimensional polymers, some of which are difficult to quantify in computer simulations of realistic (off-lattice) polymer models. But we show here that phenomena such as the greatly enlarged non-Hooke's-law elasticity present in 2D are straightforward to extract from simulation using a large-deviation framework - even though simulating that nonlinearity is tantamount to simulating a 4th order susceptibility. The large-deviation perspective includes both a set of thermodynamic-like tools suitable for studying finite-size systems and a realization that an accurate description of the system's average behavior needs to be consistent with how improbably large fluctuations would behave in that system. The latter is key because strong correlations are absent in this asymptotic large fluctuation regime, so the regime's far-reaching effects can be analytically incorporated into the analysis of simulation data. That, in turn, allows us to direct the efforts of simulations away from difficult-to-sample rare-event domains. We illustrate this point with two- and three-dimensional Monte Carlo simulations (and exact results) on two models of a single isolated polymer chain: a chain of linked hard spheres, which has long-ranged excluded volume effects, and a discretized worm-like chain, which does not.
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Soft Condensed Matter

On the chemo-thermo-mechanics of constrained reactive mixtures of solids

Alberto Salvadori, Mattia Serpelloni and Robert M. McMeeking

Building upon the classical chemo-mechanical theory of Larché and Cahn for equilibrium, numerous studies have investigated the transport of species in solids, with or without trapping phenomena. In most applications – such as the swelling of hydrogels, hydrogen embrittlement in metals, and the transport of lithium or sodium in battery electrodes – the formation of a new phase or compound can be directly associated with the concentration of the diffusing species. In the present work, we focus on the formation of solid mixtures made of multiple compounds, each characterized by its own volumetric expansion coefficient. Such a scenario arises, for instance, during the sodiation of tin anodes, among other systems. The classical chemo-mechanical framework is naturally recovered as a particular case of the proposed formulation. The theoretical framework developed herein elucidates and differentiates the concepts of phases and flowing species, while establishing rigorous connections between them. The present note is restricted to the general formulation of the governing equations, whereas application-specific developments will be addressed in forthcoming publications.
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Other Condensed Matter · Cross-listed from quant-ph

Observation of flat-band skin effect

Xulong Wang, Dongyi Wang, Congwei Lu et al. (+4 more)

Symmetry-protected ideal flat bands in one-dimensional (1D) Hermitian lattices are populated by compact localized states (CLS) - a special class of localization with wavefunctions confined within a small region. In this work, we discover that the non-Hermitian skin effect (NHSE) can appear in a flat band. Unlike conventional NHSEs for dispersive bands that are protected by nontrivial point-gap topology, the flat band remains a point on the complex-energy plane and is therefore always topologically trivial. We found that, intriguingly, the flat-band skin effect (FBSE) is associated with the non-trivial spectral topology of the dispersive bands enclosing the flat band on the complex-energy plane, so it only emerges within a finite range of non-Hermitian parameters and can counterintuitively disappear at large non-Hermiticity. Moreover, the gaps between the flat and the dispersive bands can close at higher-order exceptional points under both periodic and open boundary conditions. The flat-band wavefunctions are discontinuous in quantum distance across these exceptional points, signifying that the gap-closing is singular. The FBSE was experimentally observed in a non-Hermitian mechanical lattice. Our work reveals flat-band phenomena unique to non-Hermitian systems and highlights new possibilities in quantum geometry and localization control.
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All authors Xulong Wang, Dongyi Wang, Congwei Lu, Ruo-Yang Zhang, Ching Hua Lee, Kun Ding, Guancong Ma

Materials Science

Wave energy conversion by floating and submerged piezoelectric bimorph plates

Zachary J. Wegert, Ben Wilks, Ngamta Thamwattana et al. (+3 more)

Gaining insight into the interaction between flexible piezoelectric structures and ocean waves can inform the development of compact, high-efficiency wave-energy converters that harvest renewable energy from the marine environment. In this paper, the problem of wave energy absorption by floating and submerged piezoelectric plates is investigated. The equations of motion for a plate consisting of two piezoelectric layers separated by an elastic substrate are derived in dimensional form from the full piezoelectric constitutive laws. A solution using a modal expansion method is proposed, in which the component radiation and diffraction problems are reduced to hypersingular integral equations and solved numerically using a constant panel method. The method is general and can solve the equations of motion for submerged rigid, flexible elastic or flexible piezoelectric plates. Extensive numerical results for the energy absorption and efficiency are given for a range of parameters, including different piezoelectric materials: polyvinylidene fluoride (PVDF) and lead zirconate titanate (PZT-5H). Importantly, greater energy absorption is obtained for submerged plates when compared to plates floating on the surface. Furthermore, clamped boundary conditions give slightly larger energy absorption compared to the simply supported case. Our open-source code is provided at https://github.com/zjwegert/SemiAnalyticWECs.jl.
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All authors Zachary J. Wegert, Ben Wilks, Ngamta Thamwattana, Vivien J. Challis, Santanu Koley, Michael H. Meylan

Materials Science

Engineering a Correlated Narrow-Gap Semiconductor: Effects of Ga Substitution in EuZn$_2$P$_2$

M. Dutra, E. Marulanda, G. G. Vasques et al. (+11 more)

The effect of Ga substitution on the electronic, magnetic, and low-energy responses of the Zintl phase EuZn$_2$P$_2$ is investigated by electrical transport, electron spin resonance (ESR), and terahertz time-domain spectroscopy (THz-TDS). Incorporating Ga into EuZn$_2$P$_2$ (EuZn$_{1.8}$Ga$_{0.2}$P$_2$) reduces the electrical resistivity, indicating enhanced free-carrier density and a narrowed semiconducting gap. ESR confirms the persistence of Eu$^{2+}$ moments while showing a crossover from a Lorentzian to a Dysonian lineshape, consistent with reduced skin depth, increased carrier density, and the emergence of diffusive contributions. Ga-substituted compound display pronounced negative magnetoresistance linked to magnetic-polaron formation. THz-TDS reveals strong low-frequency absorption and a notable enhancement of the Drude conductivity in the substituted material, together with an increased carrier scattering time and enhanced carrier-density–to–effective-mass ratio. These results demonstrate that Ga substitution tunes charge transport, carrier dynamics, and short-range magnetic correlations in EuZn$_2$P$_2$, establishing EuZn$_{1.8}$Ga$_{0.2}$P$_2$ as a promising platform for engineering correlated narrow-gap magnetic semiconductors with enhanced electronic and spin-dependent functionalities.
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All authors M. Dutra, E. Marulanda, G. G. Vasques, J. F. Oliveira, P. C. Sabino, R. B. Delgado, L. Mendonça-Fereira, A. R. V. Benvenho, E. Baggio-Saitovitch, R. K. Machado, N. M. Kawahala, J. Munevar, M. A. Avila, F. G. G. Hernandez

Materials Science

A Three-Dimensional Dodecaphenylyne-Derived Carbon Allotrope with Anisotropic and Auxetic-Like Mechanical Behavior

Kleuton A. L. Lima, José A. dos S. Laranjeira, Bill D. A. Huacarpuma et al. (+4 more)

We introduce 3D-DPhyne, a novel three-dimensional (3D) carbon allotrope derived from the dodecaphenylyne framework, and investigate its structural, electronic, optical, and mechanical properties using first-principles calculations. The proposed structure forms a tetragonal, topologically complex network of four-, six-, and twelve-membered carbon rings with mixed sp/sp^2 hybridization and a formation energy of -7.87 eV/atom, comparable to other stable carbon allotropes. Phonon dispersion calculations show no imaginary modes, and ab initio molecular dynamics simulations at 1000~K confirm robust thermal stability without bond breaking. Electronic structure analysis reveals metallic character, with multiple bands crossing the Fermi level and dominant contributions from carbon p orbitals, consistent with a fully delocalized 3D $\pi$-conjugated network. The optical response is anisotropic, exhibiting strong absorption in the visible and ultraviolet regions and low reflectivity across a broad range of photon energies. Mechanical analysis reveals pronounced elastic anisotropy, with Young's modulus varying from approximately 40 to 490 GPa depending on direction. Poisson's ratio displays unconventional directional behavior, including auxetic-like responses.
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All authors Kleuton A. L. Lima, José A. dos S. Laranjeira, Bill D. A. Huacarpuma, Nicolas F. Martins, Julio R. Sambrano, Douglas S. Galvão, Luiz A. Ribeiro Jr

Superconductivity

Driving the field-free Josephson diode effect using Kagome Mott insulator barriers

Michiel P. Dubbelman, Heng Wu, Joost Aretz et al. (+9 more)

Josephson junctions (JJs), devices consisting of two superconductors separated by a barrier, are of great technological importance, being a cornerstone of quantum information processing. Classical understanding of superconductor-insulator-superconductor JJs is that conventional insulator's properties, other than magnetism, do not significantly influence the junction's behavior. However, recent work on quantum material (QM) JJs - using Mott insulator Nb3Br8 - resulted in magnetic field-free non-reciprocal superconductivity, termed the Josephson diode effect (JDE), implying the QM's intrinsic properties can modulate superconductivity in non-trivial ways. To date, the underlying mechanism and dependence of the JDE on correlation strength (U/t) has not been elucidated. Here we fabricate QMJJs using correlated Kagome insulators with varying U/t, Nb3X8 (X=Cl, Br, I), observing a decreasing trend of the field-free JDE with Nb3Cl8 reaching ~48% efficiency, Nb3Br8 ~6%, and Nb3I8 having no discernible JDE, matching the trend of decreasing U/t from Cl to I and suggesting correlation in insulators drives the field-free JDE.
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All authors Michiel P. Dubbelman, Heng Wu, Joost Aretz, Yaojia Wang, Chris M. Pasco, Yuzhou Zhao, Trent M. Kyrk, Jihui Yang, Xiaodong Xu, Tyrel M. McQueen, Malte Roesner, Mazhar N. Ali

Statistical Mechanics · Cross-listed from hep-th

Gauging Open EFTs from the top down

Greg Kaplanek, Maria Mylova and Andrew J. Tolley

We present explicit top-down calculations of Open EFTs for gauged degrees of freedom with a focus on the effects of gauge fixing. Starting from the in-in contour with two copies of the action, we integrate out the charged matter in various $U(1)$ gauge theories to obtain the Feynman-Vernon influence functional for the photon, or, in the case of symmetry breaking, for the photon and Stückelberg fields. The influence functional is defined through a quantum path integral, which – as is always the case when quantizing gauge degrees of freedom – contains redundancies that must be eliminated via a gauge-fixing procedure. We implement the BRST formalism in this setting. The in-in boundary conditions break the two copies of BRST symmetry down to a single diagonal copy. Nevertheless the single diagonal BRST is sufficient to ensure that the influence functional is itself gauge invariant under two copies of gauge symmetries, retarded and advanced, regardless of the choice of state or symmetry-breaking phase. We clarify how this is consistent with the decoupling limit where the global advanced symmetry is generically broken by the state. We illustrate our results with several examples: a gauge field theory analogue of the Caldeira-Leggett model, spinor QED with fermions integrated out, scalar QED in a thermal state, the Abelian Higgs-Kibble model in the spontaneously broken state with the Higgs integrated out, and Abelian Higgs-Kibble model coupled to a charged bath in a symmetry-broken phase. The latter serves as an example of an open system for Stückelberg/Goldstone fields.
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Statistical Mechanics

Optimal active engines obey the thermodynamic Lorentz force law

Adrianne Zhong, Adam G. Frim and Michael R. DeWeese

What are the fundamental limitations for finite-time engines that extract work from active nonequilibrium systems, and what are the optimal protocols that approach them? We show that the finite-time work extraction for nonconservative overdamped Langevin systems may be rewritten as a Lorentz force Lagrangian action, with the kinetic term corresponding to a thermodynamic metric term that is an $L_2$-optimal transport cost for the time-dependent probability density, and the magnetic field coupling term corresponding to an effective quasistatic work extraction, proving that optimal protocols counterdiabatically steer the thermodynamic state trajectory to satisfy a Lorentz force law defined on thermodynamic state space. We utilize and reinterpret classic concepts from electromagnetism in the setting of cyclical nonequilibrium processes. We show that the housekeeping heat can be controlled to be arbitrarily close to zero by minimizing nonequilibrium fluctuations. It immediately follows from our results that the constant-velocity angle clamp protocol applied to the $F_1$ molecular motor in a recent experiment [T. Mishima et al., Phys. Rev. Lett. 135, 148402 (2025)] is in fact the globally optimal protocol: it produces zero housekeeping heat while simultaneously minimizing dissipation and maximizing work transduction.
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Materials Science

Tunable Electronic Transport in Pd$_3$O$_2$Cl$_2$ Kagome Bilayers: Interplay of Stacking Configuration and Strain

Ziao Yang and Chidiebere I. Nwaogbo

Kagome lattice bilayers offer unique opportunities for engineering electronic properties through interlayer stacking and strain. We report a comprehensive first-principles study of Pd$_3$O$_2$Cl$_2$ kagome bilayers, examining four stacking configurations (AA, AA$'$, AB, AB$'$). Our calculations reveal dramatic stacking-dependent band gap modulation from 0.08 to 0.76~eV, with the AB$'$ configuration being the most thermodynamically stable. All stackings exhibit robust mechanical stability with Young's moduli of 54.82-61.97~N/m and ductile behavior suitable for flexible electronics. Carrier effective masses show significant stacking dependence, ranging from 2.39-6.35~$m_0$ for electrons and 0.67-1.55~$m_0$ for holes. Strain engineering of the AB$'$ bilayer demonstrates non-monotonic band gap tuning and asymmetric modulation of carrier masses, with hole effective masses showing stronger strain sensitivity. These results establish Pd$_3$O$_2$Cl$_2$ bilayers as a promising platform for strain-engineered kagome-based quantum devices, where stacking order and mechanical deformation provide complementary control over electronic transport.
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