Materials Science · Cross-listed from physics.optics
Elastomer-based whispering gallery mode microlasers with low Young's modulus for biosensing applications
Melisa A. Bayrak, David Ripp, Joseph S. Hill et al. (+1 more)
Sensing biological forces with microscopic
lasers is an emerging technique that offers significant advantages over conventional fluorescent probes and imaging-based techniques. However, the limited availability of suitable deformable or elastic microlaser materials is restricting the scale of forces that can be detected which strongly narrows their overall applicability. Here, we describe the synthesis of spherical whispering gallery mode microbead
lasers from a commercially available elastomer material in a microfluidic system with high viscosity. Upon doping with an organic dye, the microbeads show multimode lasing with thresholds in the range of 2-11 nJ. Measurements of the mechanical properties reveal that the width of the
laser modes is directly proportional to the applied external force. The measured mean Young's modulus is 36 kPa, comparable to the stiffness of single
cells and soft tissues. We also demonstrate that elastomer microlasers are stable under
cell culture conditions for several days and observe splitting of the
laser modes for intracellular microlasers. The observed properties render elastomer microlasers as a robust material platform for biointegrated
lasers that also allows further tuning of the mechanical and optical properties for tailored force sensing inside
cells, tissues, and small animals.
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All authors Melisa A. Bayrak, David Ripp, Joseph S. Hill, Marcel Schubert
Mesoscale and Nanoscale Physics
Minimal d-Band Model for the Optical Susceptibility of Non-Centrosymmetric Monolayer Transition Metal Dichalcogenides
Angiolo Huamán
The optical response of two-dimensional materials has been customarily calculated ab initio using plane waves basis and the full Bloch wavefunction, without separating the most important orbital contributions. In the family of monolayer transition metal dichalcogenides lacking inversion
symmetry, we take advantage of the mostly $d-$orbital content of the Bloch bands around the
semiconductor gap to reduce the calculation of their linear and quadratic optical susceptibilities to a very minimal model that includes only three energy bands. As the Bloch wavefunction determines the microscopic response to external fields, this simple approach reproduces well first principles calculations up to roughly 2 eV above the band gap. This could be the starting point for the inclusion of many-body effects with only a few energy bands in a numerically inexpensive way.
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Strongly Correlated Electrons
Orbital homology of p and t2g orbitals in models and materials
Gang v. Chen and Congjun Wu
The nominal divide between $p$- and $d$-electron systems often obscures a deep underlying unity in condensed matter physics. This review elucidates the orbital homology between the $p$ and $t_{2g}$ orbital
manifolds, establishing the correspondence that extends from minimal model
Hamiltonians to the complex behaviors of real
quantum materials. We demonstrate that despite their distinct atomic origins, these orbitals host nearly identical hopping physics and
spin-orbit coupling, formalized through an effective ${l=1}$ angular momentum
algebra for the $t_{2g}$ case. This equivalence allows one to transpose physical intuition and theoretical models developed for $p$-orbital systems directly onto the more complex $t_{2g}$ materials, and vice versa. We showcase how this paradigm provides a unified understanding of emergent phenomena, including non-trivial band
topology, itinerant ferromagnetism, and unconventional superconductivity, across a wide range of platforms, from transition metal compounds, two-dimensional
oxide heterostructures, and iron-based
superconductors, to $p$-orbital ultracold gases. Ultimately, this $p$-$t_{2g}$ homology serves not only as a tool for interpretation but also as a robust design principle for engineering novel
quantum states.
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Disordered Systems and Neural Networks · Cross-listed from physics.bio-ph
Decoding the Architecture of Living Systems
Manlio De Domenico
The possibility that evolutionary forces – together with a few fundamental factors such as thermodynamic constraints, specific computational features enabling information processing, and ecological processes – might constrain the logic of living systems is tantalizing. However, it is often overlooked that any practical implementation of such a logic requires complementary circuitry that, in biological systems, happens through complex networks of genetic regulation, metabolic reactions, cellular signalling, communication, social and eusocial non-trivial organization. We review and discuss how circuitries are not merely passive structures, but active
agents of change that, by means of hierarchical and modular organization, are able to enhance and catalyze the
evolution of evolvability. Using statistical physics to analyze the role of non-trivial
topologies in major evolutionary transitions, we show that biological innovations are related to deviation from trivial structures and (thermo)dynamic
equilibria. We argue that sparse heterogeneous networks such as hierarchical modular, which are ubiquitously observed in nature, are favored in terms of the trade-off between energetic costs for redundancy, error-correction and maintainance. We identify three main features – namely, interconnectivity, plasticity and interdependency – pointing towards a unifying framework for modeling the phenomenology, discussing them in terms of dynamical systems theory, non-
equilibrium thermodynamics and evolutionary dynamics. Within this unified picture, we also show that slow evolutionary dynamics is an emergent phenomenon governed by the replicator-mutator equation as the direct consequence of a constrained variational nonequilibrium process. Overall, this work highlights how dynamical systems theory and nonequilibrium thermodynamics provide powerful analytical techniques to study biological complexity.
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Statistical Mechanics · Cross-listed from quant-ph
Measuring out-of-time-order correlators on a quantum computer based on an irreversibility-susceptibility method
Haruki Emori and Hiroyasu Tajima
The out-of-time-ordered correlator (OTOC) is a powerful tool for probing
quantum information scrambling, a fundamental process by which local information spreads irreversibly throughout a
quantum many-body system. Experimentally measuring the OTOC, however, is notoriously challenging due to the need for time-reversed
evolution. Here, we present an experimental evaluation of the OTOC on a
quantum computer, using three distinct protocols to address this challenge: the rewinding time method (RTM), the weak-measurement method (WMM), and the irreversibility-susceptibility method (ISM). Our experiments investigate the
quantum dynamics of an XXZ
spin-1/2 chain prepared in a thermal Gibbs state. As a key contribution, we provide the first experimental demonstration of the ISM, using the trapped-ion
quantum computer, reimei. We also conduct a detailed comparative analysis of all three methods, revealing method-dependent behaviors in the measured OTOC. This work not only validates these protocols as practical tools for exploring
quantum chaos on near-term hardware but also offers crucial insights into their respective advantages and limitations, providing a practical framework for future experimental investigations.
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Strongly Correlated Electrons · Cross-listed from hep-lat
Minimal-doubling and single-Weyl Hamiltonians
Tatsuhiro Misumi
We develop a systematic
Hamiltonian formulation of minimally doubled
lattice fermions in (3+1) dimensions, derive their nodal structures (structures of zeros), and classify their
symmetry patterns for both four-component Dirac and two-component Weyl constructions. Motivated by recent single-Weyl proposals based on Bogoliubov-de Gennes (BdG) representation, we argue that the corresponding single-Weyl
Hamiltonians are obtained from the minimal-doubling
Hamiltonians supplemented by an appropriate species-splitting mass term, and we re-examine the non-onsite
symmetry protecting the physical Weyl node in terms of a Ginsparg-Wilson-type relation. We then construct a one-parameter family of deformations that preserves all the
symmetries and demonstrate that, once the parameter exceeds a critical value, additional Weyl nodes emerge and the system exits the single-node regime. This indicates that in interacting theories radiative corrections can generate
symmetry-allowed counterterms, so maintaining the desired single-Weyl phase generically requires "moderate" parameter tuning.
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Materials Science
Temperature and crystallographic orientation dependence of the anisotropic magnetoresistance in epitaxial Fe65Co35 thin films
A. Paz Jalca, W. H. Painado Lozano, D. E. Gonzalez-Chavez et al. (+7 more)
In this work, we study the anisotropic magnetoresistance (AMR) behavior of [001] epitaxial Fe65Co35 thin films along different crystallographic directions as a function of temperature. The AMR ratio is found to strongly depend on the current orientation relative to the
crystal axes, reaching 0.16 % and 0.10 % at room temperature when the current is applied along the
magnetic hard and easy axes, respectively. Moreover, the AMR ratio decreases at different rates as the temperature is reduced to 80 K. The longitudinal and transverse magnetoresistance curves were fitted using the Stoner-Wohlfarth formalism to describe the magnetization reversal path and to extract the
magnetic anisotropy constants. The fitted cubic and uniaxial anisotropy constants are Kc = -2.36 kJ/m3 and Ku = 2.18 kJ/m3, verifying the change in the cubic anisotropy compared to Fe-richer Fe100-xCox compositions. These results demonstrate that by tailoring the crystalline orientation and temperature dependence of AMR, epitaxial Fe65Co35 thin films can enable the design of
magnetic sensors with tunable sensitivity.
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All authors A. Paz Jalca, W. H. Painado Lozano, D. E. Gonzalez-Chavez, L. Saba, D. Pérez-Morelo, J. E. Gómez, A. Butera, A. Gutarra Espinoza, L. M. Leon Hilario, L. Avilés-Félix
Soft Condensed Matter
Dissociation Line and Driving Force for Nucleation of the Multiple Occupied Hydrogen Hydrate from Computer Simulation
Miguel J. Torrejon, S. Blazquez, Jesus Algaba et al. (+2 more)
In this work, we determine the dissociation temperature of the hydrogen (H$_2$) hydrate by computer simulation using two different methods. In both cases, the molecules of water and H$_2$ are modeled using the TIP4P/Ice and a modified version of the Silvera and Goldman models respectively, and the Berthelot combining rule for the cross water-H$_2$ interactions has been modified. The first method used in this work is the solubility method which consists in determining the solubility of H$_2$ in an aqueous phase when in contact with a H$_2$ hydrate (H–L$_{\text{w}}$) phase and when in contact with a pure H$_2$ phase (L$_{\text{w}}$–L$_{\text{H}_2}$) at different temperatures. At a given pressure value, both solubility curves intersect at the temperature ($T_3$) at which the three phases coexist in
equilibrium. Following this approach, we determine the dissociation temperature of the H$_2$ hydrate at $185\,\text{MPa}$ finding a good agreement with the data previously reported in the literature. We also analyze the effect of the multiple occupancy of the D, or small, and H, or large, cages of the sII hydrate structure. We conclude that the $T_3$ value is barely affected by the occupancy of the H$_2$ hydrate at $185\,\text{MPa}$. From the analysis of the solubility curves and performing extra bulk simulations of the three phases involved in the
equilibrium, we also determine the driving force for nucleation ($\Delta\mu^{\text{EC}}_{N}$) at $185\,\text{MPa}$ as a function of the supercooling degree and the H$_2$ hydrate occupancy. We determine that, thermodynamically, the most favored occupancy of the H$_2$ hydrate consists of 1 H$_2$ molecule in the D cages and 3 in the H cages (named as 1-3 occupancy).
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All authors Miguel J. Torrejon, S. Blazquez, Jesus Algaba, M. M. Conde, F. J. Blas
Quantum Gases · Cross-listed from nucl-th
Exploring Interplays Between $^3\text{P}_2$ Neutron Superfluid Vortices and $^1\text{S}_0$ Proton Fluxtubes in the Outer Core of Neutron Stars
Tatsuhiro Hattori and Kazuyuki Sekizawa
In the outer core of
neutron stars, $^3$P$_2$ superfluid
neutrons and $^1$S$_0$ superconducting
protons are deemed to exist, forming
quantum vortices and
magnetic fluxtubes, respectively. Those
quantum vortices and fluxtubes play an important role in explaining observed sudden changes of rotational frequency, known as
pulsar “glitches.” While the most of conventional glitch models rely on pinning/unpinning dynamics of
neutron $^1\text{S}_0$ superfluid
vortices in the inner crust, contributions of the outer core have not been ruled out. However, the latter possibility has been less explored so far and further thorough investigations are desired. In this study, we are thus developing a microscopic model based on
spin-2 Gross-Pitaevskii equation (GPE) for
neutron $^3$P$_2$ superfluid
vortices coupled with Ginzburg-Landau equation (GLE) for fluxtubes associated with superconducting $^1\text{S}_0$
protons. In this contribution, we outline our theoretical framework and report tentative results showing how shape of
quantum vortices could be affected by the presence of a
proton fluxtube.
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Strongly Correlated Electrons
Tunable Electronic Correlations in 135-Kagome Metals
Matteo Crispino, Niklas Witt, Stefan Enzner et al. (+4 more)
Kagome metals exhibit rich correlated-electron physics, yet a systematic understanding of the degree of correlation across transition-metal species remains elusive. Using density-functional theory plus multi-orbital slave-
spin mean-field theory, we investigate electronic correlations in the Ti-, V-, and Cr-based 135 compounds with Sb and Bi pnictogens. We find that the significantly stronger degree of correlation of the Cr-based materials compared to Ti and V can only be explained through the synergy of two effects: the larger electron filling of the $d$-shell and the reduced characteristic kinetic energy. We put forward that the substitution of Sb with Bi strengthens correlations in all compounds and make the prediction that the-yet-to-be-synthesized CsCr$_3$Bi$_5$ must be the most strongly correlated member of the entire family. These findings provide a quantitative, band-structure-based framework for understanding and predicting correlation strength in Kagome metals.
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All authors Matteo Crispino, Niklas Witt, Stefan Enzner, Tommaso Gorni, Luca de' Medici, Domenico Di Sante, Giorgio Sangiovanni
Materials Science
Unravelling 2,4-D – biochar interactions by molecular dynamics: adsorption modes and surface functionalities
Rosie Wood, Ondřej Mašek and Valentina Erastova
We report a molecular dynamics investigation of 2,4-dichlorophenoxyacetic acid (2,4-D) adsorption at the aqueous-biochar interface using experimentally constrained woody biochar models representative of softwood-derived biochars produced at 400, 600 and 800 ${\deg}$C. The models reproduce experimental descriptors (H/C, O/C, aromaticity, true density, and surface functionality) of their experimental counterparts, and simulations enable calculation of adsorption isotherms that align with available experimental measurements. Our results reveal that 2,4-D$^{-}$ uptake is governed by a synergy of three interaction classes: (i) ${\pi}$-${\pi}$ and ${\pi}$-Cl contacts with graphitic domains with either parallel or perpendicular
alignments, (ii) polar interactions including H-bonding to surface -OH and other oxygen-containing groups, and (iii) Na$^{+}$-mediated cation bridging that links 2,4-D$^{-}$ anion to surface oxygens, that would have an increasing relevance for biochars near or above the pH at point of zero charge. Notably, we found that low-temperature produced biochars, which retain higher densities of surface O functionalities, exhibit higher adsorption per unit surface area due to cooperative polar interactions alongside ${\pi}$-${\pi}$ binding, whereas medium-to-high temperature biochars rely more on ${\pi}$-${\pi}$ and cation-bridging mechanisms. The distinct adsorption distances measured emphasize surface heterogeneity and porosity. Taken together, these atomistic insights corroborate experimental observations and yield actionable guidance for the rational design of biochars for remediation of anionic herbicides, highlighting how surface functionality and solution chemistry can be tuned to optimize sorption. Our approach provides a general framework to interrogate pollutant-biochar interactions and to inform remediation strategies.
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Soft Condensed Matter
Scaled charges for ions: an improvement but not the final word for modeling electrolytes in water
S. Blazquez, M. M. Conde and C. Vega
In this work we discuss the use of scaled charges when developing force fields for NaCl in water. We shall develop force fields for Na$^+$ and Cl$^-$ using the following values for the scaled charge (in electron units) : 0.75, 0.80, 0.85, 0.92 along with the TIP4P/2005 model of water (for which previous force fields were proposed for q = 0.85 and q = 1). The properties considered in this work are: densities, structural properties, transport properties, surface tension, freezing point depression and maximum in density. All the developed models were able to describe quite well the experimental values of the densities. Structural properties were well described by models with charges equal or larger than 0.85, surface tension by the charge 0.92, maximum in density by the charge 0.85 and transport properties by the charge 0.75. The use of a scaled charge of 0.75 is able to reproduce with high accuracy the viscosities and
diffusion coefficients of NaCl solutions by the first time. We have also considered the case of KCl in water and the results obtained were fully consistent with those of NaCl. There is no value of the scaled charge able to reproduce all the properties considered in this work. Although certainly scaled charges are not the final word in the development of force fields for electrolytes in water its use may have some practical advantages. Certain values of the scaled charge could be the best option when the interest is to describe certain experimental properties.
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Quantum Gases
Fast collisional $\sqrt{\mathrm{SWAP}}$ gate for fermionic atoms in an optical superlattice
Rafi Weill, Jonathan Nemirovsky and Yoav Sagi
Collisional gates in optical superlattices have recently achieved record fidelities, but their operation times are typically limited by tunneling. Here we propose and analyze an alternative route to a fast $\sqrt{\mathrm{SWAP}}$ gate for two fermionic atoms in an optical superlattice based on optimized, time-dependent control of the short and long
lattice depths. The gate is implemented by transiently releasing the atoms into a quasi-harmonic confinement centered between the two sites. With an appropriately chosen contact interaction strength, a controlled collision accumulates the exchange phase required for $\sqrt{\mathrm{SWAP}}$ and generates
entanglement. We employ a continuum, time-dependent Schrödinger-equation simulation that goes beyond a two-site
Fermi–Hubbard description and
benchmark it against experimentally implemented tunneling-based protocols, reproducing the observed single-particle tunneling and
spin-exchange dynamics. For experimentally accessible
lattice depths, we find that the proposed gate operates in $\sim 21\,\mu\mathrm{s}$, more than an order of magnitude faster than tunneling-based implementations, while achieving fidelities $\gtrsim 99\%$. We further analyze sensitivity to
lattice-depth variations and show that a composite sequence improves robustness. Our results establish fast, collision-mediated entangling gates in superlattices as a promising building block for scalable neutral-atom
quantum computation.
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Disordered Systems and Neural Networks
Sparse Interactions Reshape Stability in Random Lotka-Volterra Dynamics
Mattia Tarabolo, Luca Dall'Asta and Roberto Mulet
Classical approaches to ecological stability rely on fully connected interaction models, yet real ecosystems are sparse and structured–a feature that qualitatively reshapes their collective dynamics. Here, we establish a thermodynamically exact stability phase diagram for generalized Lotka-Volterra dynamics on sparse random graphs, resolving how finite connectivity and interaction heterogeneity jointly govern ecosystem resilience. Using a small-coupling expansion of the dynamic cavity method, we derive an effective single-site
stochastic process that is solvable via population dynamics. Our approach uncovers a topological phase transition–driven purely by the finite connectivity structure of the network–that leads to multi-stability. This instability is fundamentally distinct from the disorder-driven transitions induced by quenched randomness of the couplings. Our framework overcomes the considerable computational cost of direct simulations, offering a scalable and versatile analysis of stability, biodiversity, and alternative stable states in realistic, large-scale ecological ecosystems.
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Statistical Mechanics
Structural changes in the Lennard-Jones supercooled liquid and ideal glass: an improved integral equation for the replica method
Bomont Jean-Marc, Bretonnet Jean-Louis, Costa Dino et al. (+1 more)
Framing the glass formation within standard statistical mechanics is an outstanding problem of condensed matter theory. To provide new insight, we investigate the structural properties of the Lennard-Jones fluid in the very-low temperature regime, by using a replicated version of the refined HMSA theory of the
liquid state, combined with an appropriate split of the pair potential [Bomont and Bretonnet, J. Chem. Phys. 114, 4141 (2001)]. Our scheme allows one to reach an unprecedented low-temperature domain within both the supercooled
liquid and the ideal-glass phase. Therein, a density-dependent temperature is identified, whereupon the radial distribution function experiences clear-cut structural changes, insofar as an additional peak develops in between the main and the second peaks. Such a structural feature points to a local structure of the Lennard-Jones ideal glass with an fcc-like short-range order, in the absence of any long-range order.
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All authors Bomont Jean-Marc, Bretonnet Jean-Louis, Costa Dino, Pastore Giorgio
Soft Condensed Matter
Thermally Activated Non-Affine Rearrangements in Amorphous Glass: Emergence of Intrinsic Length Scales
Avinash Kumar Jha
We present a systematic study of temperature-driven nonaffine rearrangements in a model amorphous solid across the full thermodynamic range, from a high-temperature
liquid, through supercooled and sub-glass regimes, into deep glassy states. The central result is a quantitative characterisation of the componentwise nonaffine residual displacements, obtained by subtracting local affine maps from particle displacements. For each state point the tails of the probability distributions of these nonaffine components display clear exponential decay; linear fits to the logarithm of the tail region yield characteristic nonaffine length scales {\xi}NA,x and {\xi}NA,y , which quantify the spatial extent of purely nonaffine, local rearrangements. To compare with other length scales, we compute van Hove distributions Gx(ux), Gy (uy ) which capture the full particle displacement field (coherent affine-like motion plus residuals). A robust, key finding is that the van Hove length scale consistently exceeds the filtered nonaffine length scale, i.e. {\xi}VH > {\xi}NA, across all temperatures, state points, and densities we studied. The nonaffine length {\xi}NA quantifies the distance over which complex deformation occurs, specifically nonlinear and anharmonic responses, irreversible (plastic) rearrangements, topological non-recoverable particle rearrangements, and other residual motions that cannot be represented by a local affine map. Moreover, near equality of {\xi}NA,x and {\xi}NA,y in all conditions provides further evidence that nonaffine rearrangements propagate isotropically under thermally driven deformation in contrast to externally driven shear.
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Materials Science · Cross-listed from cs.AI
Multi-AI Agent Framework Reveals the "Oxide Gatekeeper" in Aluminum Nanoparticle Oxidation
Yiming Lu, Tingyu Lu, Di Zhang et al. (+2 more)
Aluminum nanoparticles (ANPs) are among the most energy-dense solid fuels, yet the atomic mechanisms governing their transition from passivated particles to explosive reactants remain elusive. This stems from a fundamental computational bottleneck: ab initio methods offer
quantum accuracy but are restricted to small spatiotemporal scales (< 500 atoms, picoseconds), while empirical force fields lack the reactive fidelity required for complex combustion environments. Herein, we bridge this gap by employing a "human-in-the-loop" closed-loop framework where self-
auditing AI
Agents validate the
evolution of a machine learning potential (MLP). By acting as scientific sentinels that visualize hidden model artifacts for human decision-making, this collaborative cycle ensures
quantum mechanical accuracy while exhibiting near-linear scalability to million-atom systems and accessing nanosecond timescales (energy RMSE: 1.2 meV/atom, force RMSE: 0.126 eV/Angstrom). Strikingly, our simulations reveal a temperature-regulated dual-mode oxidation mechanism: at moderate temperatures, the
oxide shell acts as a dynamic "gatekeeper," regulating oxidation through a "breathing mode" of transient nanochannels; above a critical threshold, a "rupture mode" unleashes catastrophic shell failure and explosive combustion. Importantly, we resolve a decades-old controversy by demonstrating that aluminum cation outward
diffusion, rather than oxygen transport, dominates mass transfer across all temperature regimes, with
diffusion coefficients consistently exceeding those of oxygen by 2-3 orders of magnitude. These discoveries establish a unified atomic-scale framework for energetic nanomaterial design, enabling the precision engineering of ignition sensitivity and energy release rates through intelligent computational design.
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All authors Yiming Lu, Tingyu Lu, Di Zhang, Lili Ye, Hao Li
Strongly Correlated Electrons
Magnetic field and pressure tuning of the heavy fermion antiferromagnet CePdIn
Bin Shen, Feng Du, Rui Li et al. (+8 more)
Frustrated Kondo
lattices are ideal platforms for studying how both the Kondo effect and
quantum fluctuations compete with the
magnetic exchange interactions that drive
magnetic ordering. Here, we investigate the effect of tuning the heavy-
fermion compound CePdIn, which crystallizes in the geometrically frustrated ZrNiAl-type structure, using applied
magnetic fields and hydrostatic pressure. At ambient pressure, CePdIn exhibits two
magnetic transitions, one at $T_{\rm{N}} \approx 1.65$ K and another at $T_{\rm{M}} \approx 1.15$ K, which are both suppressed by applied $c$-axis fields. Upon applying pressure in zero
magnetic field, there is a non-monotonic
evolution of $T_{\rm{N}}$, which decreases to 0.8 K at 2.3 GPa, before abruptly increasing to 1.5 K at 2.6 GPa. At higher pressures, $T_{\rm{N}}$ has a weak pressure dependence, and vanishes near 5 GPa. Together with the high-pressure phase being more robust to applied fields, these results suggest two distinct
antiferromagnetic phases in CePdIn, which are separated near 2.6 GPa, and this change may be driven by the
evolution of the underlying electronic structure due to enhanced Kondo hybridization under pressure.
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All authors Bin Shen, Feng Du, Rui Li, Hang Su, Yasuyuki Shimura, Takahiro Onimaru, Kazunori Umeo, Xin Lu, Toshiro Takabatake, Michael Smidman, Huiqiu Yuan
Strongly Correlated Electrons
Light-induced trion-exciton competition revealed by ultrafast photoemission
Ittai Sidilkover, Nir Hen Levin, Yuval Nitzav et al. (+11 more)
Strong Coulomb interactions in low-dimensional
quantum materials give rise to emergent bound states such as
excitons and trions. Trions are conventionally secondary excitations, requiring both optical excitation and charge doping. In quasi-one-dimensional Ta$_2$NiS$_5$, however, an exceptionally large binding energy exceeding the single-particle band gap stabilizes an
equilibrium trion gas under surface doping alone. Here, using time- and angle-resolved photoemission spectroscopy, we show that trions can also be generated purely optically, without external charge. Following photoexcitation of pristine Ta$_2$NiS$_5$ we observe a bright, momentum-localized, in-gap feature with a slow, fluence-dependent relaxation. Rate-equation modeling identifies it as a mixed population of trions and
excitons, with the trions formed via an unconventional single-particle pathway that requires no photoexcited hole. The trion-
exciton composition is controlled by pump fluence, with trions dominating the late-time relaxation. In surface doped samples, the same model with unchanged rates reproduces the full dynamics, linking the light-induced trions to their
equilibrium counterparts through pump-induced dissociation and recapture. These results establish trARPES as a direct probe of charged quasiparticles far from
equilibrium and open routes to optical control of neutral and charged excitations in correlated materials.
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All authors Ittai Sidilkover, Nir Hen Levin, Yuval Nitzav, Shiri Gvishi, Abigail Dishi, Shaked Rosenstein, Noam Ophir, Irena Feldman, Andrei Varykhalov, Naaman Amer, Amit Kanigel, Anna Keselman, Iliya Esin, Hadas Soifer
Materials Science · Cross-listed from quant-ph
Quantum Noise Spectroscopy of Nanoscale Charge Defects in Silicon Carbide at Room Temperature
Jinpeng Liu, Yuanhong Teng, Yu Chen et al. (+11 more)
The nanoscale charge environment critically influences the performance of
semiconductor devices, yet traditional characterization techniques usually lack the spatial resolution to resolve nanoscale charge heterogeneity and identify microscopic noise sources. Here, we address this critical gap by utilizing individual PL5 color centers in commercial silicon carbide as room-temperature, broadband (near-DC to GHz)
quantum spectrometers. We report the first real-time, nanoscale observation of single-charge tunneling dynamics at room temperature in 4H-SiC by monitoring the random telegraph noise using optically detected
magnetic resonance (ODMR). This capability enables an electrical noise imaging technique that shows distinct noise variations on different wafers. Employing dynamical decoupling and $T_1$ relaxation spectroscopy, we observe correlations of noise spectral density across frequency bands and obtain the nanoscale electron paramagnetic resonance (EPR) fingerprint of
spin defects in SiC. Ultimately, through surface chemical engineering, we identify the native
oxide layer as the main source of resolved electromagnetic fluctuations. This work establishes a versatile atomic-scale metrology platform bridging
quantum sensing and
semiconductor engineering, offering critical insights for optimizing third-generation
semiconductor interfaces and advancing solid-state
quantum technologies.
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All authors Jinpeng Liu, Yuanhong Teng, Yu Chen, Yixuan Wang, Sen Luan, Chihang Luo, Jun Yin, Hao Li, Lixing You, Qiang Li, Chunming Yin, Ya Wang, Qi Zhang, Fazhan Shi
Materials Science
Chemical state detection and charge transfer in complex oxide heterostructures via in situ Auger Electron Spectroscopy
Harish Kumarasubramanian and Jayakanth Ravichandran
Understanding and controlling the chemical states both in the bulk and at the interfaces of complex
oxide thin films is essential for engineering a wide range of electronic, optical, and
magnetic functionalities, which arise through emergent phenomena such as two-dimensional electron gases, interfacial magnetism, and associated phase transitions. Here, we demonstrate the use of in situ Auger Electron Spectroscopy (AES) as a powerful tool for probing oxidation states and dynamic chemical processes during the growth of complex
oxide heterostructures. By leveraging the chemical sensitivity of AES to subtle changes in valence electron populations, we show that this technique can distinguish distinct oxidation states in multivalent perovskite manganate and vanadate systems with high fidelity during deposition. Furthermore, we show evidence for dynamic chemical phenomena, specifically charge transfer processes at the polar-nonpolar LaMnO3/SrTiO3 interface. Our results establish in situ AES as a powerful diagnostic tool for monitoring and controlling interfacial chemistry during thin film growth, offering a pathway toward the atomic-scale engineering of chemical states in functional
oxide heterostructures.
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Mesoscale and Nanoscale Physics
Hf/Zr Superlattice-Based High-ąppa} Gate Dielectrics with Dipole Layer Engineering for Advanced CMOS
Taeyoung Song, Sanghyun Kang, Yu Hsin Kuo et al. (+7 more)
Advanced logic transistors require gate dielectrics that achieve sub-nanometer equivalent
oxide thickness (EOT), suppress leakage, and satisfy three key requirements: (i) compatibility with RMG-like high-temperature processing, (ii) sufficient Vth tunability for multi-Vth design, and (iii) high device reliability. However, meeting all of these requirements simultaneously has been difficult with conventional high-k systems. In this work, we demonstrate that Hf/Zr-based gate stacks quantitatively satisfy these conditions. After a 700 C N2 anneal, the HZH superlattice achieves an EOT of 7.3 A, lower than conventional HfO2-only stacks (8.5 A) while maintaining comparable leakage.
Embedding a 3 A Al2O3 dipole within an HfO2/ZrO2/HfO2 superlattice (HZHA) breaks the conventional dipole trade-off, achieving an EOT of 8.4 A, lower than the 9.0 A of a standard HfO2/Al2O3 stack, while providing a flatband voltage shift greater than 200 mV, thereby enabling multi-Vth tuning without compromising scaling. Furthermore, under -2 V negative-bias temperature stress at 125 C for 100 s, HZHA and HA exhibit comparable flatband voltage drifts of 87 mV and 97 mV, respectively, confirming that strong Vth tunability and sub-nanometer EOT can be achieved without compromising stability. In addition to these quantitative advances, this study reveals previously unreported physical insights into dipole behavior and interfacial
diffusion in ultrathin Hf/Zr multilayers. These results establish HZHA as an RMG-compatible, Vth-tunable, low-EOT dielectric platform capable of supporting logic scaling beyond the 1 nm frontier.
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All authors Taeyoung Song, Sanghyun Kang, Yu Hsin Kuo, Jiayi Chen, Lance Fernandes, Nashrah Afroze, Mengkun Tian, Hyoung Won Baac, Changhwan Shin, Asif Islam Khan
Soft Condensed Matter
A Dynamical Trap Made of Target-Tracking Chasers
Guo-Jie Jason Gao
We propose a dynamical trapping system composed of multiple chasers subject to target-tracking forces utilizing the velocity and position information of a single escaping target. To successfully capture the target, dividing chasers into multiple groups while each group approaching its assigned destination in the proper vicinity of the target is essential. Moving direction synchronization between the target and its chasers is crucial to the capturing process, while guiding chasers to the predicted position of the target in future only improves the efficiency of capture but is not indispensable. Potential applications of our trapping system include capturing live animals such as bears invading a human residential area.
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Materials Science
Kitaev interaction and possible spin liquid state in CoI2 and Co2/3Mg1/3I2
Yaozhenghang Ma, Ke Yang, Yuxuan Zhou et al. (+1 more)
Kitaev materials are of great interest due to their potential in realizing
quantum spin liquid (QSL) states and applications in topological
quantum computing. In the pursuit of realizing Kitaev QSL, a Mott
insulator with strong bond-dependent frustration and weak
geometric frustration is highly desirable. Here we explore Kitaev physics in the van der Waals triangular antiferromagnet (AF) CoI$_2$, through the
spin-orbital states and Wannier function analyses, exact diagonalization and density
matrix renormalization group study of the electronic structure and
magnetic properties. We find that the high-
spin Co$^{2+}$ ion is in the $J_\mathrm{eff}=1/2$ state because of strong
spin-orbit coupling, and the weak trigonal elongation and
crystal field contribute to the observed weak in-plane
magnetic anisotropy. The strong $t_{2g}$-$e_g$ hopping via the strong Co 3$d$-I 5$p$ hybridization gives rise to a strong Kitaev interaction ($K_1$) at the first nearest neighbors (1NN), and the long Co-Co distance and the weak $t_{2g}$-$t_{2g}$ hoppings determine a weak Heisenberg interaction $J_1$. The resultant $|K_1/J_1|$ = 6.63 confirms a strong bond-dependent frustration, while the
geometric frustration due to the 3NN Heisenberg interaction $J_3$ gets involved, and they all together result in the experimental helical AF order in CoI$_2$. We then propose to suppress the $J_3$ using a partial Mg substitution for Co, and indeed we find that Co$_{2/3}$Mg$_{1/3}$I$_2$ has the much reduced
geometric frustration but hosts the robust bond-dependent frustration, and thus it would be a promising Kitaev material being so far closest to the QSL state.
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All authors Yaozhenghang Ma, Ke Yang, Yuxuan Zhou, Hua Wu
Strongly Correlated Electrons · Cross-listed from hep-th
On Gauging Finite Symmetries by Higher Gauging Condensation Defects
Yuan Xue, Eric Y. Yang and Zipei Zhang
Based on the work by Córdova-Costa-Hsin (arXiv:2412.16681), we propose an EFT-style, Lagrangian procedure to gauge finite 0-form
symmetries in untwisted Dijkgraaf-Witten gauge theories on closed oriented
manifolds using higher gauging condensation defects and point out its limitations. Using this proposal, we construct effective actions of untwisted Dijkgraaf-Witten theories with Heisenberg gauge group over $\mathbb{Z}_p$ and show that the braiding data from
Hopf link and the fusion rules match with the expected discrete gauge theories. We also study the symTFT implications of these effective Lagrangians and clarify their relations with higher group global
symmetries.
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Superconductivity
Effect of superconductivity by Nb and V substitution in kagome CaPd5
Dan Li, Zhengxuan Wang, Chuanguang Zhang et al. (+8 more)
Materials featuring kagome
lattices have attracted significant research interest due to their unique
geometric frustration, which gives rise to rich physical phenomena such as non-trivial
topology,
spin fluctuations, and superconductivity. In this work, using CaPd5 as the prototype structure, we discover and systematically investigate a new class of kagome
superconductors, CaMxPd5-x (M = Nb and V)
alloys. First-principles calculations confirm that these compounds are non-
magnetic metals, among which four are dynamically stable: CaNb5, CaV5, CaNb2Pd3, and CaV2Pd3. CaNb5 is identified as a strong electron-
phonon coupling (EPC)
superconductor with the highest superconducting transition temperature (Tc) of 10.1 K, which can be further increased to 12.8 K under external pressure. In contrast, CaV5, CaNb2Pd3, and CaV2Pd3 exhibit weaker EPC and correspondingly lower Tc values. Furthermore, by applying the method of
symmetry indicators, we systematically classify the topological and nodal characteristics of CaNb5, providing valuable insights for determining its superconducting pairing
symmetry. Our findings demonstrate that Nb and V substitution in kagome CaPd5 provides an effective route for designing a new type of kagome
superconductor with relatively high Tc. This study also offers new perspectives on topological superconductivity in kagome systems and establishes a useful guideline for discovering other superconducting materials with unique properties.
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All authors Dan Li, Zhengxuan Wang, Chuanguang Zhang, Chunlan Ma, Shijing Gong, Chuanxi Zhao, Shuaikang Zhang, Tianxing Wang, Xiao Dong, Wuming Liu, Yipeng An
Materials Science
The Role of THz Phonons in the Ionic Conduction Mechanism of $Li_7La_3Zr_2O_{12}$ Polymorphs
Amy K. Lin, Lauren F. Illa, Natan A. Spear et al. (+2 more)
Superionic conduction in solid-state materials is governed not only by static factors, such as structure and composition, but also by dynamic interactions between the mobile ion and the
crystal lattice. Specifically, the dynamics of
lattice vibrations, or
phonons, have attracted interest because of their hypothesized ability to facilitate fast ionic conduction. Herein, we use
laser-driven ultrafast impedance spectroscopy (LUIS) to resonantly excite
phonons using a THz field and probe ion hopping with picosecond time resolution. We apply LUIS to understand the dynamical role of
phonons in $Li_7La_3Zr_2O_{12}$ (LLZO). When in its cubic phase (c-LLZO), this garnet-type solid electrolyte has an ionic conductivity two orders of magnitude greater than its tetragonal phase (t-LLZO). Upon excitation of
phonons in the 0.5-7.5 THz range, the ionic conductivity of both polymorphs is enhanced. Furthermore, we observe a similar time decay constant of the perturbation between t-LLZO and c-LLZO despite their distinct Li sublattices and migration mechanisms. Along with Raman spectra and MD-computed vibrational density of states, these findings suggest that low-energy optical
phonons perturb the
lattice to enhance ionic conduction independently of the underlying static properties. We propose that it does so by increasing the population of
phonons which directly modulate the ion hopping pathway and by increasing the
entropy of migration thereby partially counteracting the migration barrier set by the Li sublattice. Overall, this work highlights the interplay of static and dynamic factors that enables improved ionic conductivity in both highly and poorly conducting inorganic solids alike.
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All authors Amy K. Lin, Lauren F. Illa, Natan A. Spear, Geoffrey A. Blake, Scott K. Cushing