Strongly Correlated Electrons
Automorphism in Gauge Theories: Higher Symmetries and Transversal Non-Clifford Logical Gates
Po-Shen Hsin and Ryohei Kobayashi
Gauge theories are important descriptions for many physical phenomena and systems in
quantum computation.
Automorphism of gauge group naturally gives global
symmetries of gauge theories. In this work we study such
symmetries in gauge theories induced by
automorphisms of the gauge group, when the gauge theories have nontrivial topological actions in different spacetime dimensions. We discover the
automorphism symmetry can be extended, become a higher group
symmetry, and/or become a non-invertible
symmetry. We illustrate the discussion with various models in field theory and on the
lattice. In particular, we use
automorphism symmetry to construct new transversal non-Clifford logical gates in topological
quantum codes. In particular, we show that 2+1d $\mathbb{Z}_N$ qudit Clifford stabilizer models can implement non-Clifford transversal logical gate in the 4th level $\mathbb{Z}_N$ qudit Clifford hierarchy for $N\geq 3$, extending the generalized Bravyi-König bound proposed in the companion paper [arXiv:2511.02900] for
qubits.
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Materials Science
Electrical Modulation and Probing of Antiferromagnetism in Hybrid Multiferroic Heterostructures
Yuhan Liang, Huiping Han, Hetian Chen et al. (+11 more)
The unique features of ultrafast
spin dynamics and the absence of macroscopic magnetization in
antiferromagnetic (AFM) materials provide a distinct route towards high-speed
magnetic storage devices with low energy consumption and high integration density. However, these advantages also introduce challenges in probing and controlling AFM order, thereby restricting their practical applications. In this study, we demonstrate an all-electric control and probing of the AFM order in heavy metal (HM)/AFM
insulator (AFMI)
heterostructures on a ferroelectric substrate at room temperature (RT). The AFM order was detected by the anomalous
Hall effect (AHE) and manipulated by the ferroelectric field effect as well as the piezoelectric effect in
heterostructures of Pt/NiO/0.7Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$–0.3PbTiO$_{3}$ (PMN–PT). The non-volatile control of AFM order gives rise to a 33% modulation of AHE, which is further evidenced by synchrotron-based X-ray
magnetic linear dichroism (XMLD). Combined with the $in$-$situ$ piezoelectric response of AHE, we demonstrate that ferroelectric polarization contributes mainly to the control of the AFM order. Our results are expected to have broader implications for efficient spintronic devices.
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All authors Yuhan Liang, Huiping Han, Hetian Chen, Yujun Zhang, Yi Zhang, Chao Li, Shun Lan, Fangyuan Zhu, Ji Ma, Di Yi, Jing Ma, Liang Wu, Tianxiang Nan, Yuan-Hua Lin
Superconductivity
Moiré-induced gapped phases in twisted nodal superconductors
Kevin P. Lucht, J. H. Pixley and Pavel A. Volkov
We demonstrate the emergence of gapped phases driven by the moiré superlattice that trivialize the topological states in twisted nodal
superconductors. The effect arises from umklapp tunneling between non-adjacent Dirac points in momentum space close to specific twist angles or chemical potentials, determined by the
Fermi surface geometry. We confirm the robustness of the non-topological phase against interactions with self-consistent calculations and show that this gap competes with the previously predicted topological gapped phases, leading to topological phase transitions. These transitions were overlooked in prior literature, signifying the necessity of modifying the phase diagrams of topological phases exhibited in twisted nodal
superconductors with and without an interlayer current. We also estimate the relevant twist angles and discuss experimental signatures, focusing on twisted Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$
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Strongly Correlated Electrons · Cross-listed from hep-th
Real-time Scattering in \phi^4 Theory using Matrix Product States
Bahaa Al Sayegh and Wissam Chemissany
We investigate the critical behavior and real-time scattering dynamics of the interacting $\phi^4$
quantum field theory in (1+1)-dimensions using uniform
matrix product states (uMPS) and the time-dependent variational principle (TDVP). A finite-
entanglement scaling analysis at $\lambda = 0.8$ bounds the critical mass-squared to $\mu_c^2 \in ]-0.2595,-0.2594[$ and provides a quantitative map of the symmetric, near-critical, and spontaneously broken regimes. Using these ground states as asymptotic
vacua, we simulate two-particle collisions in a sandwich geometry and extract the elastic scattering probability $P_{11\to 11}(E)$ and Wigner time delay $\Delta t(E)$ using a sandwich geometry protocol. We find strongly inelastic scattering in the symmetric phase ($P_{11\to 11} \simeq 0.712$, $\Delta t \simeq -158$ for $\mu^2 = +0.2$) and almost perfectly elastic collisions in the spontaneously broken phase ($P_{11\to 11} \simeq 1$, $\Delta t \simeq -108$ for $\mu^2=-0.1$ and $P_{11\to 11} \simeq 1$, $\Delta t \simeq -177.781$ for $\mu^2=-0.5$). Crucially, the scattering protocol exhibits a distinctive divergence near the critical coupling; we show that this behavior serves as a dynamical signature of the
quantum critical point, arising directly from the closing of the mass gap. These results demonstrate that TDVP-based uMPS can effectively probe nonperturbative scattering and critical dynamics in
lattice field theories with controlled
entanglement truncation.
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Statistical Mechanics
Demon with dementia - the deterioration of information transcription
Maggie Williams, Emery Doucet and Sebastian Deffner
In introductory biology, aging is typically explained as a result of mutations during the DNA replication process within
cells. Upon abstraction, we recognize that cellular aging can be understood as the gradual decay in fidelity of information transcription. Since cellular processes are microscopic and inherently
stochastic, the abstracted process of information transcription can be understood using Markovian dynamics. In our work, we model the process of information transcription with an autonomous Maxwell's demon (AMD) which interacts with two bitstreams, a lifted mass, and a heat reservoir. As main results, we analyze the steady-state properties of the system with both time-independent and time-dependent transition rates, focusing on the statistics of extractable work, bit transcription fidelity, and two-bit mutual information. Together, these results provide a holistic view of a simplified model for DNA transcription as an information-theoretic process.
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Strongly Correlated Electrons
Intrinsic quantum disorder in Yb2Ti2O7 and the quantum S=1/2 pyrochlore phase diagram
Shang-Shun Zhang, Anish Bhardwaj, S.M. Koohpayeh et al. (+4 more)
We present an experimental and theoretical study of the anisotropic pyrochlore phase diagram. Inelastic field-dependent
neutron scattering on Yb$_2$Ti$_2$O$_7$ shows intrinsic broadening and a flat low-energy
magnon mode which is partially captured by interacting
magnon models. Exact diagonalization reveals the existence of an emergent
quantum phase between ferromagnetism and antiferromagnetism, in which Yb$_2$Ti$_2$O$_7$
Hamiltonian potentially resides. This behavior matches the phenomenology of
quantum criticality in heavy
fermion systems, and shows Yb$_2$Ti$_2$O$_7$ is a clean system which can be field-tuned from well-defined
magnons to a nontrivial
quantum ground state. This suggests that
quantum criticality is a generic feature of the dipolar phase diagram.
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All authors Shang-Shun Zhang, Anish Bhardwaj, S.M. Koohpayeh, D.M. Pajerowski, Jeffrey G. Rau, Hitesh J. Changlani, Allen Scheie
Strongly Correlated Electrons
Magnetic electron-hole asymmetry in cuprates: a computational revisit
Jiong Mei, Shao-Hang Shi, Ping Xu et al. (+5 more)
In this work, we revisit the electron-hole asymmetry of antiferromagnetism in cuprates by studying the three-band Emery model. Using parameters relevant to La$_2$CuO$_4$, we
benchmark the anti-
ferromagnetic response for a large range of dopings with variational Monte Carlo, determinant
quantum Monte Carlo, constrained-path auxiliary-field
quantum Monte Carlo, density-
matrix embedding theory, and the Gutzwiller approximation. Across methods and accessible sizes/temperatures, we find no significant electron-hole asymmetry if we consider only Neel anti-ferronagnetic response and ignore other possible orders such as stripe state. This result is robust to a moderate oxygen-site repulsion $U_p$ and to parameter sets of Nd$_2$CuO$_4$. Incorporating dopant-induced local potentials reveals an extrinsic route to asymmetry: Cu-site defects enhance AFM on the electron-doped side, whereas O-site defects suppress it on the hole-doped side. These results indicate that dopant-driven effects make a non-negligible contribution to apparent electron-hole asymmetry in the general phase diagram of cuprates and should be included when analyzing competing orders in cuprates.
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All authors Jiong Mei, Shao-Hang Shi, Ping Xu, Ziyan Chen, Hui-Ke Jin, Mingpu Qin, Zi-Xiang Li, Kun Jiang
Statistical Mechanics · Cross-listed from math.AP
Kinetic and mean-field modeling of muscular dystrophies
Tommaso Lorenzi, Horacio Tettamanti and Mattia Zanella
We present a new class of models for assessing the
cell dynamics characterising muscular dystrophies. The proposed approach comprises a system of integro-differential equations for the statistical distributions, over a large patient cohort, of the densities of muscle fibers and immune
cells implicated in muscle inflammation, degeneration, and regeneration, which underpin disease development. Considering an appropriately scaled version of this model, we formally derive, as the corresponding mean-field limit, a system of Fokker-Planck equations, from which we subsequently derive, as a macroscopic model counterpart, a system of differential equations for the mean densities of muscle and immune
cells in the cohort of patients and the related variances. Then, we study long-time asymptotics for the mean-field model by determining the quasi-
equilibrium cell distribution functions, which are in the form of probability density functions of inverse Gamma distributions, and proving the long-time convergence to such quasi-
equilibrium distributions. The analytical results obtained are illustrated by means of a sample of results of numerical simulations. The modeling approach presented here has the potential to offer new insights into the balance between degeneration and regeneration mechanisms in the progression of muscular dystrophies, and provides a basis for future extensions, including the modeling of therapeutic interventions.
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Strongly Correlated Electrons
Structural phase transitions in the van der Waals ferromagnets Fe$_x$Pd$_{y}$Te$_2$
Rafaela F. S. Penacchio, Siham Mohamed, Sérgio L. Morelhão et al. (+3 more)
Here, we provide a detailed study of the
crystal structure and physical properties of the recently discovered vdW ferromagnet FePd$_2$Te$_2$. We find this compound has a relatively wide width of formation, and grow single
crystals with compositions Fe$_x$Pd$_{y}$Te$_2$ where $x$ ranges from 0.9 to 1.1 and $y$ from 1.8 to 2.5, respectively. Temperature-dependent X-ray diffraction and transport measurements reveal that a first-order structural transition occurs in the range of $T$ = 360-420 K. Above the transition, the compounds with Pd fraction $y>2$ adopt a disordered derivative of the tetragonal FeTe structure, with the Fe layer showing mixed Fe/Pd occupancy and the extra Pd atoms partially occupying interstitial sites. Below 370 K, the structure is incommensurately modulated. For $y<2$, the composition Fe$_{1.1}$Pd$_{1.8}$Te$_2$ has monoclinic
symmetry at room temperature that is consistent with the reported structure of FePd$_2$Te$_2$. This phase undergoes a structural transition at 420 K for which the high temperature structure is yet to be determined; however, based on the similarities with the $y > 2$ compounds, we speculate that this composition also adopts a tetragonal structure above 420\,K. All compounds investigated in the Fe$_x$Pd$_{y}$Te$_2$ series show metallic behavior, with
magnetic characterization indicating that they are easy-plane, hard, ferromagnets with $T_C$ spanning 98–180 K. Both the critical temperature for the structural transition and the Curie temperature are moderately suppressed with increasing Pd fraction $y$ and corresponding decreasing Fe fraction $x$, indicating that synthetic control over $x$ and $y$ paves way for the further exploration of these compounds.
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All authors Rafaela F. S. Penacchio, Siham Mohamed, Sérgio L. Morelhão, Sergey L. Bud'ko, Paul C. Canfield, Tyler J. Slade
Mesoscale and Nanoscale Physics
Stability bounds for the generalized Kadanoff-Baym ansatz in the Holstein dimer
O. Moreno Segura, Y. Pavlyukh and R. Tuovinen
Predicting real-time dynamics in correlated systems is demanding: exact two-time Green's function methods are accurate but often too costly, while the Generalized Kadanoff-Baym Ansatz (GKBA) offers time-linear propagation at the risk of uncontrolled behavior. We examine when and why GKBA fails in a minimal yet informative setting, the Holstein dimer that describes electron-
phonon coupling. Using a conserving, fully self-consistent electron-
phonon self-energy, we map out parameter regions where GKBA dynamics is stable and where it becomes unstable. We trace the onset of these failures to qualitative changes in the model's ground-state solutions obtained from the full nonequilibrium Green's function theory, thereby providing practical stability bounds for GKBA time
evolution. We further show that coupling the dimer to electronic leads can damp and, in part, cure these instabilities. The results supply simple diagnostics and guidelines for reliable GKBA simulations of electron-
phonon dynamics.
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Superconductivity · Cross-listed from quant-ph
Experimental demonstration of non-local magic in a superconducting quantum processor
Halima Giovanna Ahmad, Gianluca Esposito, Viviana Stasino et al. (+9 more)
Non-local magic is the non-stabilizerness that no local
unitary operation can erase. It captures the joint action of
entanglement and magic underlying
quantum advantage, and it has never been measured on
quantum hardware. Here we report its first experimental demonstration, on a superconducting
quantum processing unit, through two independent routes: an optimal local-erasure protocol and a direct, state-agnostic measurement of subsystem purity. The two agree with each other and with theory. Exploiting direct access to the device, we construct a noise model with no free parameters that identifies readout error and a depolarizing controlled-Z channel as the dominant mechanisms, and we show that local and non-local magic can be addressed separately, erasing local magic in situ while preserving the non-local part. Non-local magic provides a hardware
benchmark beyond standard gate-fidelity protocols and points toward more reliable pre-fault tolerant devices.The same tools underlie a purity-estimation protocol with exponential speedup and the decoding of Hawking radiation in a black-hole toy model.
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All authors Halima Giovanna Ahmad, Gianluca Esposito, Viviana Stasino, Jovan Odavic, Carlo Cosenza, Alessandro Sarno, Pasquale Mastrovito, Michele Viscardi, Stefano Cusumano, Francesco Tafuri, Davide Massarotti, Alioscia Hamma
Superconductivity
Recent progress of scanning tunneling microscopy/spectroscopy study of pair density wave in superconductors
Zi-Ang Wang, Bin Hu, Xianghe Han et al. (+2 more)
A pair density wave (PDW) is a superconducting state characterized by an order parameter with finite center-of-mass momentum in the absence of an external
magnetic field, thereby breaking the conventional translational
symmetry in homogeneous
superconductors. It is proposed that PDW emerges from
magnetic interactions, strong electron-electron correlations, and their interplay with competing orders. In this review, we highlight recent advances in the detection and study of PDWs using scanning tunneling microscopy and spectroscopy (STM/STS). We focus on how the signatures of PDW have been experimentally visualized across a variety of extraordinary
superconductors, including iron-based
superconductors, cuprate
superconductors,
spin-triplet
superconductors, kagome-
lattice superconductors, and transition metal dichalcogenides. Beginning with an introduction to the fundamental concept of PDWs and the unique capabilities of STM/STS, particularly its atomic-scale spatial resolution and advanced data analysis techniques, we discuss key experimental findings, including the direct visualization of charge density modulations associated with PDWs. Finally, we discuss emerging challenges and future directions, aiming to inspire future research into the nature of PDWs in
superconductors.
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All authors Zi-Ang Wang, Bin Hu, Xianghe Han, Hui Chen, Hong-Jun Gao
Strongly Correlated Electrons
Gustavo M. Yoshitome and Pedro R. S. Gomes
We discuss the emergence of non-Abelian zero modes from twist defects in Abelian topological phases. We consider a setup built from a fractional
quantum Hall (or a fractional Chern
insulator)-
superconductor heterostructure, which effectively induces a phase transition, leading to a topological phase endowed with new anyonic
symmetries, and accordingly supporting distinct types of zero modes at fixed filling. These defects are modeled at the interface between two copies of the same
heterostructure arranged side by side, which produces counterpropagating modes that can be gapped by interactions that realize the anyonic
symmetries. We characterize the parafermions associated with each anyonic
symmetry and discuss how their presence affect the periodicity of Josephson tunneling current.
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Superconductivity
Atomic Visualization of Bulk and Surface Superconductivity in Weyl Semimetal {\gamma}-PtBi2
Hao Zhang, Hui Chen, Zichen Huang et al. (+8 more)
A bulk
superconductor hosting intrinsic surface superconductivity provides a unique platform to study Majorana bound states. The
superconductor, trigonal {\gamma}-PtBi2, is a promising candidate, as surface superconducting gaps and topological surface states have been observed. However, the simultaneous presence of bulk and surface superconductivity has not been resolved. Here, we directly visualize coexisting bulk and surface superconducting gaps in trigonal PtBi2 by using ultra-low-temperature scanning tunneling microscopy/spectroscopy. The bulk gap is {\Delta} ~ 0.053 meV with a critical temperature (Tc) ~ 0.5 K and a critical field below 0.01 T, accompanied by a
vortex lattice and bound states, yielding a coherence length of ~200 nm. Remarkably, certain surface regions show a much larger gap of {\Delta} ~ 0.42 meV, persisting up to Tc ~ 3 K and surviving
magnetic fields up to 2 T, yet lacking a static
vortex lattice. This coexistence of robust surface and bulk superconductivity establishes {\gamma}-PtBi2 as a unique platform for investigating the interplay between bulk and surface Cooper pairings in superconducting topological materials.
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All authors Hao Zhang, Hui Chen, Zichen Huang, Zi-Ang Wang, Guangyuan Han, Ruisong Ma, Xiangde Zhu, Wei Ning, Chengmin Shen, Qing Huan, Hong-Jun Gao
Statistical Mechanics · Cross-listed from math-ph
Inhomogeneous SSH models and the doubling of orthogonal polynomials
Nicolas Crampé, Quentin Labriet, Lucia Morey et al. (+2 more)
We analyze Su-Schrieffer-Heeger (SSH) models using the doubling method for orthogonal
polynomial sequences. This approach yields the analytical spectrum and exact eigenstates of the models. We demonstrate that the standard SSH model is associated with the doubling of Chebyshev
polynomials. Extending this technique to the doubling of other finite sequences enables the construction of
Hamiltonians for inhomogeneous SSH models which are exactly solvable. We detail the specific cases associated with Krawtchouk and $q$-Racah
polynomials. This work highlights the utility of
polynomial-doubling techniques in obtaining exact solutions for physical models.
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All authors Nicolas Crampé, Quentin Labriet, Lucia Morey, Gilles Parez, Luc Vinet
Superconductivity
Interplay of spin-orbit coupling and trigonal crystal field enhances superconductivity in $LaAlO_3/KTaO_3$ (111)
Long Cheng, Jia Liu, Tongying Liu et al. (+10 more)
In conventional
superconductors, bulk physical properties typically degrade as the film thickness approaches the two-dimensional (2D) limit. Here in the (111) oriented LaAlO3/KTaO3 (LAO/KTO)
heterostructure, we demonstrate experimental evidence that reducing the conducting layer thickness at the interface significantly enhances superconducting transition temperature Tc, in direct contrast to conventional wisdom. From the sum frequency generation (SFG) spectroscopy and superconducting upper-critical field measurements, both the trigonal
symmetry and
spin orbit scattering are enhanced with the increased Tc. We attribute the enhanced superconductivity (SC) to the synergic interplay between
spin-orbit coupling (SOC) and trigonal
crystal field, resulting in an enhanced electron-
phonon coupling. Furthermore, we show the existence of unconventional SC: the approaching linear temperature dependence of normal state resistance with increasing Tc and the existence of a
quantum critical point (QCP) near the superconducting phase. Our findings provide important insight into the underlying mechanism of the strong orientation-dependent KTO interface SC.
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All authors Long Cheng, Jia Liu, Tongying Liu, Pan Chen, Mingyue Zhang, Jiashi Li, Shiyu Zhang, Fei Ye, Qing Wang, Weitao Liu, Jian Kang, Jiandi Zhang, Xiaofang Zhai
Superconductivity
Tuning Bound States of Symmetry-Breaking Vortices via Unidirectional Charge Density Wave in a Transition-Metal Dichalcogenide Superconductor
Hao Zhang, Hui Chen, Zichen Huang et al. (+6 more)
The interplay between charge density wave (CDW) and superconducting
vortex bound states are crucial for fundamental physics of superconductivity and advancing
quantum nanotechnologies. However, the CDW-mediated modulation of
vortex bound states, which opens up a new platform for
vortex engineering, remains unexplored. Here, we report spatially anisotropic
vortex states modulated by the unidirectional CDWs in a transition-metal dichalcogenide
superconductor 1T”-NbTe2 using ultra-low-temperature scanning tunneling microscopy/spectroscopy. The stripe-like 3x1x3 CDW order exhibits a robust three-dimensional character across step edges and coexists with superconductivity below a critical temperature of 0.4 K. Under out-of-plane
magnetic fields, we observe elliptical
vortices whose elongation aligns with the CDW stripes, indicating strong coupling between
vortex morphology and underlying electronic order. Remarkably, CDW domain boundaries induce abrupt changes in
vortex orientation and
vortex bound states, enabling controllable
vortex states across CDW nanodomains. These findings establish a new pathway for manipulating superconducting
vortex bound states via CDW coupling.
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All authors Hao Zhang, Hui Chen, Zichen Huang, Zi-Ang Wang, Senhao Lv, Guoyu Xian, Hui Guo, Haitao Yang, Hong-Jun Gao
Mesoscale and Nanoscale Physics
Impact of Carrier Injector Design on the Threshold of Interband Cascade Lasers
T. Sato, B. Petrović, R. Weih et al. (+5 more)
We theoretically investigate how the injector region design of interband cascade
lasers (ICLs) impacts the threshold carrier and current densities. The model combines a polarization-sensitive 8-band $\mathbf{k}\cdot\mathbf{p}$ calculation, electrostatics, and a microscopic calculation of Auger recombination rates. The inelastic carrier-carrier scattering is included to lowest order using quasi-
equilibrium Green's functions. It captures the combined effects of charge-carrier redistribution, parasitic absorption, and bias voltage on the Auger recombination rate. We show that heavily doping the electron injector suppresses the dominant multi-hole Auger recombination by reducing the hole population of the recombination
quantum wells. This agrees with the experimental observation that the heavy doping reduces threshold currents. Unlike the measurements, however, they do not increase at high doping concentrations in our model, which does not include scattering-mediated carrier escape and/or light absorption. Furthermore, by introducing indium to the conventional $\mathrm{Ga}\mathrm{Sb}$ hole injector wells, we explain the rule of thumb from experiments that raising the hole injector levels does not outperform the doping strategy. Our model provides physical insights for optimizing ICL carrier injectors.
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All authors T. Sato, B. Petrović, R. Weih, F. Hartmann, S. Höfling, S. Birner, C. Jirauschek, T. Grange
Soft Condensed Matter
A thermo-mechanically coupled finite deformation model for freezing-induced damage in soft materials
Ali Saeedi, Ram Devireddy and Mrityunjay Kothari
In the U.S., approximately 17 patients die each day awaiting an organ transplant, a crisis driven by the inability to store organs long-term via methods like cryopreservation. A primary failure mechanism is the severe thermo-mechanical damage tissues experience during freezing. A predictive understanding of this damage is hindered by the complex interplay between heat transfer, phase change, and large deformation mechanics. Motivated by this fundamental problem, we present a fully coupled, thermo-mechanical phase-field framework for modeling damage
evolution in fluid-saturated soft materials under cryogenic conditions. The theoretical framework integrates heat transfer with solid-
liquid phase transition, finite deformation nonlinear elasticity, and progressive mechanical damage. The governing equations are solved using FEniCS finite element package. The presentation will detail the theoretical framework and showcase representative simulations that capture the spatiotemporal
evolution of temperature, freezing phase field, stress, and damage fields during representative freezing protocols. The developed framework serves as a powerful tool for understanding the fundamental mechanisms of freezing-induced injury and for designing improved cryopreservation strategies.
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Strongly Correlated Electrons
Evolution of correlated electronic states of La2NiO4 under hydrostatic pressure
Shu-Hong Tang, Han-Yu Wang, Da-Yong Liu et al. (+4 more)
We elucidate the electronic structure and
quantum many-body instabilities of the monolayer nickelate La2NiO4 under hydrostatic pressure using a combination of density functional theory, dynamical mean-field theory (DFT+DMFT), and random phase approximation (RPA). Our DFT+DMFT calculations reveal non-
Fermi-
liquid behavior and coherence loss near the
Fermi level at low pressures, driven by strong electron correlations within the Ni-e_g orbital
manifold, which is analogous to the low-energy electronic properties observed in La3Ni2O7. However, multi-orbital
spin susceptibility analysis demonstrates an exceptionally suppressed critical Stoner parameter U_c (about 0.4~0.7 eV), indicating robust
magnetic order that dominates the ground state and precludes superconductivity in the pristine system. Below U_c, superconducting instabilities exhibit a pressure-driven
symmetry transition: the d_(x2-y2)-wave pairing prevails at ambient and low pressure, while the s+g-wave
symmetry occurs above 75 GPa. This transition is attributed to pressure-induced self-doping effect. The high-angular-momentum g-wave component incurs significant energetic penalties, rendering high-Tc superconductivity unlikely. We conclude that the absence of superconductivity in La2NiO4 arises from its robust intrinsic magnetism and the unfavorable pairing
symmetry under pressure, suggesting that alternative routes-such as chemical doping or epitaxial strain-are necessary to suppress magnetism and unlock superconducting states.
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All authors Shu-Hong Tang, Han-Yu Wang, Da-Yong Liu, Feng Lu, Wei-Hua Wang, H.-Q. Lin, Liang-Jian Zou
Mesoscale and Nanoscale Physics
Long-Range Magnetic Order in Structurally Embedded Mesospin Metamaterials
Christina Vantaraki, Oier Bikondoa, Matías P. Grassi et al. (+11 more)
Engineered assemblies of interacting
magnetic elements-
magnetic metamaterials-provide a powerful route to tailor collective
magnetic order and dynamics. By structuring matter at the mesoscale, they bridge atomic magnetism and macroscopic functionality, enabling emergent behaviour inaccessible in conventional materials. However, realizing large-area metamaterials that combine high morphological uniformity with intrinsic long-range order has remained challenging, largely due to the structural disorder inherent to lithographic fabrication. Here we demonstrate a scalable route to structurally and magnetically coherent metamaterials by
embedding iron-ions to form mesospins within a non-
magnetic thin film palladium host
matrix. Using controlled implantation, we realize morphologically uniform arrays that spontaneously develop extended
antiferromagnetic order in the as-fabricated state - without the need of external annealing or field cycling. Resonant X-ray scattering and microscopy reveal sharp
magnetic Bragg peaks modulated by the mesospin form factor, evidencing long-range
antiferromagnetic order coupled to structural coherence. This embedded architecture establishes a platform for exploring coherent
spin-
photon interactions and functional X-ray scattering in
magnetic metamaterials free from lithographic topography and disorder.
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All authors Christina Vantaraki, Oier Bikondoa, Matías P. Grassi, Brindaban Ojha, Alkaios Stamatelatos, Natalia Kwiatek-Maroszek, Miguel Angel Niño Orti, Michael Foerster, Thomas Saerbeck, Daniel Primetzhofer, Max Wolff, Nicolas Jaouen, Thomas P. A. Hase, Vassilios Kapaklis
Mesoscale and Nanoscale Physics
Experimental and Theoretical Aspects of the Fragmentation of Carbon's Single and Multi-Walled Nanotubes
Sumera Javeed and Shoaib Ahmad
Energetic ion irradiation is an effective method for studying how single and multi-shelled carbon nanotubes break apart. The energy from ions is dissipated through both linear and nonlinear processes in the nanotubes, leading to defect formation. Fragmentation occurs via atomic collision cascades and thermal spikes, each described by different theoretical models. Experiments with Cs-irradiated nanotubes support these models, and an information-theoretic approach further explains the fragmentation mechanisms. Sputtered species yield probability distributions, which are analyzed using Shannon
entropy and fractal dimension to assess spatial characteristics. Kullback-Leibler divergence helps identify the diversity of emission mechanisms. Together, thermal and information-theoretic models clarify and distinguish the roles of collision cascades and thermal spikes in nanotube fragmentation.
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Strongly Correlated Electrons
On flat bands in the $J_1$-$J_2$-$J_3$ XXZ sawtooth chain
Vadim Ohanyan, Johannes Richter, Michael Sekania et al. (+3 more)
We consider a generalization of the XXZ model on the sawtooth
spin chain with Dzyaloshinskii-Moriya interactions in which all exchange constants (symmetric, antisymmetric, and axial anisotropy) are different for the three different bonds of each triangle. We derive and resolve algebraic constraints on the exchange constants ensuring the appearance of a flat band in the one-
magnon spectrum. The properties of the corresponding flat
magnon bands and localized
magnon states are analyzed. We further construct the mapping of the flat-band conditions for the Dzyaloshinskii-Moriya constants onto the Katsura-Nagaosa-Balatsky parameters. Based on the mapping, the possibility of the electric-field-driven flat bands with the aid of the magnetoelectric coupling is examined.
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All authors Vadim Ohanyan, Johannes Richter, Michael Sekania, Lucas Giambattista, Alexei Andreanov, Marcus Kollar
Strongly Correlated Electrons
Spinon excitations and spin correlations in the one-dimensional quantum magnet $\beta$-VOSO$_4$ probed by Raman spectroscopy
Dirk Wulferding, Diana Lucia Quintero-Castro, Pontus Laurell et al. (+3 more)
Fractionalized excitations such as spinons and anyons have emerged as a central theme in condensed matter physics with broad implications for superconductivity,
quantum statistics, and
quantum computation. The nearly ideal one-dimensional $S=1/2$ system $\beta$-VOSO$_4$ without long-range order down to 85 mK provides a promising platform to experimentally explore such fractionalized excitations. Here, we employ Raman spectroscopy to probe
magnetic excitations and the
evolution of
spin correlations in $\beta$-VOSO$_4$. Spinon signatures are found along the chain direction, evidenced by a broad, gapless scattering continuum at low temperatures. The temperature dependence of the spinon spectral weight aligns considerably with numerical density
matrix renormalization group calculations. By comparing the experimental spinon spectral weight with calculated results and evaluating the associated
quantum Fisher information (QFI) therefrom, we observe a steep increase in QFI upon cooling, indicating rapidly growing correlation lengths. Our study showcases QFI as a probe of
spin correlations in
quantum magnets.
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All authors Dirk Wulferding, Diana Lucia Quintero-Castro, Pontus Laurell, Gonzalo Alvarez, Elbio Dagotto, Kwang-Yong Choi
Other Condensed Matter
Some attempts toward 3-dimensional Phyllotaxy
Rémy Mosseri and Jean-François Sadoc
This paper investigates several distinct attempts to generalize in higher dimension the standard 2-dimensional phyllotaxy set construction. We first recall known contructions for these sets on $2D$
manifolds of constant
curvature (the Euclidean plane $\mathbb{R}^2$, the sphere $\mathbb{S}^2$ and the
hyperbolic plane $\mathbb{H}^2$). We then propose a first attempt to get a $3D$ phyllotactic set by piling up suitably shifted Euclidean $2D$ phyllotactic sets. A different, radially triggered, solution is then analyzed. An interesting phyllotactic set on the hypersphere $\mathbb{S}^3$ is then generated using a
Hopf fibration approach. Finally,a simple 4-dimensional example is presented, generated as a simple product of two 2-dimensional planar sets. A $3D$ phyllotaxy candidate is then derived by applying a "Cut and Project"
algorithm.
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Materials Science
Mode selectivity in electron promoted vibrational relaxation of chemisorbed hydrogen on molybdenum and tungsten surfaces
Nils Hertl, Connor L. Box and Reinhard J. Maurer
Electron-
phonon coupling in atoms and molecules adsorbed at metal surfaces gives rise to finite vibrational linewidths in infrared or electron energy loss spectra. When it is the dominant contribution to the vibrational lifetime, it manifests itself in the form of a Fano line shape. Here, we report the linewidths of vibrational modes of chemisorbed hydrogen on the (100) and (110) surfaces of molybdenum and tungsten calculated from first-order time-dependent perturbation theory. For those modes with a Fano line shape, our results are in good agreement with the experiment. We further observe that the coupling strength between vibrations and electrons depends on the nature of the mode: for Lorentzian-shaped peaks, the experimental linewidths are always larger than those predicted based on pure electron-
phonon coupling. The calculated linewidths exhibit a strong coverage dependence, decreasing towards higher coverages. This finding has important implications for nonadiabatic energy dissipation in hydrogen dynamics at metal surfaces. While electron-hole pair excitation is the dominant energy-transfer mechanism between hydrogen and pristine metal surfaces, other channels for energy dissipation, such as adsorbate-adsorbate interactions, may become more significant on metal surfaces densely covered with hydrogen.
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Materials Science
Mechanistic study of mixed lithium halides solid state electrolytes
Davide Tisi, Sergey Pozdnyakov and Michele Ceriotti
Lithium halides with the general formula Li$_x$M$_y$X$_6$, where M indicates metal ions and X halide anions are very actively studied as solid-state electrolytes, because of relatively low cost, high stability and Li conductivity. The structure and properties of these halide-based solid electrolytes (HSE) can be tuned by alloying, e.g. using different halides and/or transition metals simultaneously. The large chemical space is difficult to sample by experiments, making simulations based on broadly applicable machine-learning interatomic potentials (MLIPs) a promising approach to elucidate structure-property relations, and facilitate the design of better-performing compositions. Here we focus on the Li$_3$YCl$_{6x}$Br$_{6(1-x)}$ system, for which reliable experimental data exists, and use the recently-developed PET-MAD universal MLIP to investigate the structure of the
alloy, the interplay of crystalline
lattice, volume and chemical composition, and its effect on Li conductivity. We find that the distribution of Cl and Br atoms is only weakly correlated, and that the primary effect of alloying is to modulate the
lattice parameter – although it can also trigger transition between different
lattice symmetries. By comparing constant-volume and constant-pressure simulations, we disentangle the effect of
lattice parameter and chemical composition on the conductivity, finding that the two effects compensate each other, reducing the overall dependency of conductivity on
alloy composition. An extended study of the effect of metal substitution, enabled by the semi-quantitative accuracy of the universal model, shows that the effect of metal-site alloying is small, indicating that alloying can be used to optimize cost, or electrochemical stability, without major impact on bulk conductivity.
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Statistical Mechanics
Exact Analytical Results for the 1D Ising Chain with Periodic Impurity Fields
Malek Telfah and Abdalla Obeidat
We present an exact analytical solution for the one-dimensional Ising model in the presence of an external
magnetic field applied periodically to every $k$-th site. The problem is handled using the symmetrized transfer
matrix approach, we derive a compact closed-form expression for the system's
eigenvalues for arbitrary period $k$. From the resulting free energy, we obtain exact expressions for the magnetization and zero-field susceptibility. Explicit results are presented for $k = 1$, $k = 2$, and $k = 3$ which is considered a novel result. We further analyze the
spin-
spin correlation functions, deriving the correlation length and the set of position-dependent correlation strength prefactors, $A_{ij}$. The framework highlights how
impurity spacing suppresses thermodynamic responses, with susceptibility scaling as $\chi \sim \beta / k$ for large $k$, offering insights into diluted
magnetic systems and serving as a
benchmark for quasiperiodic modulations. The correlation strengths exhibit a strong anisotropy, revealing a complex, non-local structure of
spin fluctuations. These results provide a complete and rigorous
benchmark for understanding the effects of periodic modulation in 1D systems.
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Mesoscale and Nanoscale Physics
Dynamic stabilisation of mesospin chains
Damjan Dagbjartsson, Simon Banks and Björgvin Hjörvarsson
We present a rare example of a one-dimensional system with short-range range interactions for which a self-stabilizing long-range ordered phase persists to finite temperatures. Our model offers a new perspective on the origins of shape anisotropy on the mesoscopic scale in
magnetic metamaterials. Specifically, we show how the combination of a physically realistic stray-field potential and the spatial dimensionality of the system can reduce the effective dimensionality of classical
magnetic mesospins. The resulting emergent constraints on the
magnetic excitation spectrum underpin the observed ordering, in stark contrast to the behaviour of analogous one-dimensional models with strictly isotropic
spins.
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Soft Condensed Matter
Shaping the aggregates of discotic particles with directional pair interactions
B. Martínez-Haya, N. Morillo and A. Cuetos
Aggregation processes in systems of planar macromolecules and colloids drive a broad range of phenomena in natural systems and soft materials. Depending on chemical architecture, intermolecular interactions in these systems may favor different relative pair orientations, such as stacking face-face or percolating edge-edge arrangements. In this work, we employ a versatile coarse-grained interaction model for disk-like particles to provide a general framework to rationalize the thermotropic formation of aggregates and predict the
topology of the resulting suprastructures. Monte Carlo and Brownian Dynamics simulations show that, with an appropriate tuning of the interactions, discotics spontaneously nucleate into clusters with globular, planar or stacked geometries, leading to materials with specific internal order and associated physicochemical properties.
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