Mesoscale and Nanoscale Physics · Cross-listed from physics.chem-ph
Singlet Fission among two Single Molecules
Sumanta Paul, Oleksandr Yampolskyy, Zehua Wu et al. (+2 more)
Singlet fission (SF) is a photophysical process where a singlet excitation generates two triplet excited states, enhancing
exciton multiplication potentially useful for
solar energy conversion. Since SF typically outcompetes radiative decay, single molecule studies of SF have remained elusive. Here, we present single molecule spectroscopy of a terrylenediimide (TDI) dimer at room and cryogenic temperatures. By analysing the stream of
photons emitted by single dimers, the rates of formation and decay of SF-born triplet states were determined. We report considerable static and dynamic heterogeneities of the SF process which are reflected in broad rate distributions as well as the occasional occurrence of delayed fluorescence and rate fluctuations during
spin evolution. Cryogenic experiments point to the formation of a coherent multiexciton superposition state which decays into the singlet
exciton from which a correlated triplet pair evolves. Our results establish single molecule spectroscopy as a new avenue into mechanistic details of the SF process which often are drowned by ensemble av-eraging.
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All authors Sumanta Paul, Oleksandr Yampolskyy, Zehua Wu, Klaus Müllen, Thomas Basché
Soft Condensed Matter
On the problem of simple shear of an incompressible viscoelastic solid under finite deformations
Vladislav V. Kozhukhov
In the framework of a viscoelastic material model, whose constitutive relation is given by a one-parameter family of Gordon-Schowalter derivatives, the problem of simple shear under acceleration and random velocity motion is considered. For motion with acceleration, the presence of non-zero normal stresses is discovered, which corresponds to the Poynting effect previously discovered for this material. A problem in which the shear rate was determined as a linear function of a random variable given from a normal distribution was studied. Within the framework of the methodology proposed by V.A. Lomakin, an analytical solution of the problem is constructed. A significant dependence of the dispersion of the stress tensor components on the choice of the objective derivative was found.
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Quantum Gases · Cross-listed from nucl-th
Local Quantum Cooling for Large Fermi Systems with Pairing
J. E. Alba-Arroyo, Daniel Pęcak, Michael McNeil Forbes et al. (+1 more)
We present a framework for local
quantum cooling that can be efficiently applied to large-scale
Fermi systems. The method introduces local Hermitian operators as a cooling potential while strictly preserving the unitarity of time
evolution. Our formulation scales favorably with system size and can be seamlessly integrated into time-dependent density-functional theory frameworks. We demonstrate that energy cooling arises from the damping of particle currents and pairing-field fluctuations. Furthermore, we develop a variant of the scheme that allows the particle number to vary in time, enabling controlled density scans. The method is generic and versatile, as illustrated by applications to
spin-imbalanced
unitary Fermi gases and to
nuclear matter in the
neutron-
star crust. The framework can be naturally extended to include
stochastic noise, providing a foundation for studying thermalization in strongly interacting
Fermi superfluids.
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All authors J. E. Alba-Arroyo, Daniel Pęcak, Michael McNeil Forbes, Gabriel Wlazłowski
Mesoscale and Nanoscale Physics
Magnetic topological textures in nonorientable surfaces
Carlos Saji, Mario A. Castro, Vagson L. Carvalho-Santos et al. (+3 more)
Topological
magnetic textures confined to two-dimensional (2D) non-orientable
manifolds exhibit behaviors absent in planar systems. We investigate bimerons on Möbius surfaces and show that the lack of global orientation alters conservation laws, yielding geometry-dependent
topology and dynamics. Micromagnetic simulations reveal that the helical twist and non-orientable geometry reshape the effective topological charge and stabilize
chiral configurations imposed by the surface. Under
spin-polarized currents, bimerons display unconventional transport: the transverse response is locally reversed or globally suppressed due to charge inversion along the
manifold. Moreover, we establish an Aharonov-Bohm effect associated with the magnonic modes of the texture; in particular, the translational Goldstone mode implies that a bimeron on a Möbius strip should exhibit path-dependent
quantum interference. These results identify a geometry-driven regime of magnetization dynamics and provide a route to
curvature-engineered spintronic functionalities.
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All authors Carlos Saji, Mario A. Castro, Vagson L. Carvalho-Santos, Eduardo Saavedra, Alvaro S. Nunez, Roberto E. Troncoso
Materials Science
Crossover Dynamics of Non-Fickian Ionic Diffusion in Solids
Gangbin Yan, Pierfrancesco Ombrini, Zhichu Tang et al. (+14 more)
Ionic
diffusion in solids is central to energy storage, electronics, and catalysis, yet its chemical origins are difficult to resolve because conventional
diffusion models struggle with effects of confinement, crystallographic disorder,
lattice distortions, and coupling to electronic or phononic carriers. These challenges are especially pronounced in battery materials, where ionic and electronic motion occur together, complicating interpretation of electrochemical measurements. Here we use tracer exchange as a direct, non-electrochemical probe to reveal distinct ion-transport regimes in the one-dimensional conductor olivine Li_xFePO4 (0 <= x <= 1). Lithium isotope exchange validates single-file
diffusion governed by strong ion-ion correlations, where 1D confinement suppresses bypassing and preserves spatial order. Kinetic Monte Carlo simulations and chronoamperometry quantify both Faradaic and non-Faradaic surface exchange, identifying electron transport, rather than Li+ mobility, as the rate-limiting step for electrochemical reaction. In addition, Li-Na exchange exhibits apparent superdiffusion, with rates that increase with Na content. Simulations attribute this behavior to surface-exchange limitations and Na-induced
lattice strain that enhances cross-channel Li+ hopping and drives a crossover from 1D to quasi-2D transport. Four-dimensional STEM, in situ synchrotron XRD, X-ray absorption spectroscopy, and Mossbauer spectroscopy confirm that
lattice softening and concerted polaron motion contribute to the observed dynamics. These results establish tracer exchange as a powerful tool for probing coupled ion-electron transport and provide chemical insight into how
lattice mechanics and multicomponent exchange shape ionic
diffusion in solids.
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All authors Gangbin Yan, Pierfrancesco Ombrini, Zhichu Tang, Shakul Pathak, Maoyu Wang, Barbara Lavina, Alexandros Vasileiadis, Suin Choi, Mingzhan Wang, Dongchen Ying, Qizhang Li, Esen E. Alp, Hua Zhou, Martin Z. Bazant, Qian Chen, Marnix Wagemaker, Chong Liu
Materials Science
To crack, or not to crack: How hydrogen favors crack propagation in iron at the atomic scale
Aleksei Egorov, Lei Zhang, Erik van der Giessen et al. (+1 more)
Steel is a key structural material because of its considerable strength and ductility. However, when exposed to hydrogen, it is prone to embrittlement. Mechanistic understanding of the origin of hydrogen embrittlement is hampered by the lack of reliable interatomic potentials. Here, we perform large-scale molecular dynamics simulations of crack propagation after having developed and validated an efficient yet density-functional-theory-accurate machine-learning potential for hydrogen in iron. Simulations based on our potential reveal that in the absence of H, iron is intrinsically ductile at finite temperatures with crack-tip blunting assisted by dislocation emission. By contrast, minute (part-per-million) hydrogen concentrations can switch the crack-tip behavior from ductile blunting to brittle propagation. Detailed analysis of our molecular dynamics results reveals that the combination of fast hydrogen
diffusion and diminished surface energy is at the origin of embrittlement. Our results set the stage for a modified Griffith's criterion for hydrogen-induced brittle fracture, which closely captures the simulations and that can be used to assess embrittlement in iron-based
alloys.
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All authors Aleksei Egorov, Lei Zhang, Erik van der Giessen, Francesco Maresca
Materials Science · Cross-listed from eess.SY
Sensitivity increase of 3D printed, self-sensing, carbon fibers structures with conductive filament matrix due to flexural loading
Matei Drilea, Alexander Dijkshoorn, Gusthavo Ribeiro Salomão et al. (+2 more)
The excellent structural and piezoresistive properties of continuous carbon fiber make it suitable for both structural and sensing applications. This work studies the use of 3D printed, continuous carbon fiber reinforced beams as self-sensing structures. It is demonstrated how the sensitivity of these carbon fiber strain gauges can be increased irreversibly by means of a pretreatment by pre-stressing the sensors with a large compressive bending load. The increase in the gauge factor is attributed to local progressive fiber failure, due to the combination of the thermal residual stress from the printing process and external loading. The coextrusion of conductive filament around the carbon fibers is demonstrated as a means of improving the reliability, noise and electrical connection of the sensors. A micrograph of the sensor cross section shows that the conductive filament contacts the various carbon fiber bundles. All-in-all, the use of pre-stressing carbon fiber strain gauges in combination with coextrusion of conductive filament hold promises for 3D printed structural sensors with a high sensitivity.
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All authors Matei Drilea, Alexander Dijkshoorn, Gusthavo Ribeiro Salomão, Stefano Stramigioli, Gijs Krijnen
Materials Science
Observation of magnetically coupled electro-optic effect in LiNbO3/LiTaO3 at room temperature
Yalong Yu, Hengwei Zhang, Xiaoyan Liu et al. (+1 more)
The magnetoelectric coupling effect serves as a crucial bridge between electrical and
magnetic order parameters in condensed matter physics, forming the physical basis for the development of next-generation low-power information storage and sensing technologies. However, material systems exhibiting this effect at room temperature are extremely rare, and the coupling strength is typically very weak, which has long hindered the practical application of such phenomena despite their rich tunability. Here, we break this by reporting a pronounced magnetoelectric phenomenon,the magnetically coupled EO effect in the classic ferroelectric optical materials LiNbO3 and LiTaO3. We trace its origin to an unexpected source,the problematic direct current drift,a major reliability issue in photonic integrated
circuits. We unambiguously demonstrate that this drift stems not from mobile ions but from defect-bound unpaired electrons, whose slow polarization relaxation is quenched upon the
magnetic-field-induced formation of a room-temperature skyrmion states, as directly visualized by Lorentz transmission electron microscopy. This collective
spin ordering not only solves the decades-old drift problem but also transforms the defect states into a magnetically responsive platform, exhibiting an efficiency up to 34 pm/V in LiNbO3 and 15 pm/V in LiTaO3-an orders-of-magnitude enhancement over conventional room-temperature magnetoelectric responses and even surpassing the materials' intrinsic Pockels coefficients. We also measured the
magnetic response of this additional electro-optical effect and found that under the condition of applying a
magnetic field of 0.1 T, an electro-optical coefficient adjustment of about 8 pm/V can be achieved (0.008 pm/V/Oe), which is equivalent to 30% of the electro-optical coefficient of LiNbO3 itself.
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All authors Yalong Yu, Hengwei Zhang, Xiaoyan Liu, Tao Chu
Strongly Correlated Electrons
Hund's coupling driven nature of magnetism in negative charge transfer material, $\mathrm{SrCoO_3}$
Jyotsana Sharma, Shivani Bhardwaj and Sudhir K Pandey
In this work, we investigate the microscopic origin of magnetism in $\mathrm{SrCoO_3}$ by incorporating electronic correlations within the dynamical mean-field theory (DMFT) framework. We note a remarkable agreement of the calculated
magnetic observables ( saturation magnetization $\sim$2.4 $\mu_B$;
magnetic transition temperature, $T_c$$\sim$350 K) with the experimental results. The system exhibits Hund's coupling-induced strong quasiparticle mass enhancements of upto $m^*/m$ $\sim$7 for Co 3$d$ states, with the largest renormalization occurring in the majority
spin $t_{2g}$ orbitals, marking the onset of orbital-selectivity. Our results reveal a Stoner-$like$ collapse of exchange splitting that drives the loss of long-range
ferromagnetic order at $T_c$. The breakdown of
Fermi-
liquid behavior down to $T$$\sim$100 K suggests a suppressed coherence scale. Local
magnetic moment originates from a mixed-
spin configuration formed through dynamical fluctuation between intermediate-
spin and high-
spin states. Large charge fluctuations ($\langle$$\Delta$N$^2$$\rangle$$\sim$0.6) together with heavy quasiparticles establish the correlation effects regime, governed predominantly by Hund's physics in $\mathrm{SrCoO_3}$.
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Disordered Systems and Neural Networks · Cross-listed from q-bio.NC
Random matrix theory of sparse neuronal networks with heterogeneous timescales
Thiparat Chotibut, Oleg Evnin and Weerawit Horinouchi
Training recurrent neuronal networks consisting of excitatory (E) and inhibitory (I) units with additive noise for working
memory computation slows and diversifies inhibitory timescales, leading to improved task performance that is attributed to emergent marginally stable
equilibria [PNAS 122 (2025) e2316745122]. Yet the link between trained network characteristics and their roles in shaping desirable dynamical landscapes remains unexplored. Here, we investigate the Jacobian
matrices describing the dynamics near these
equilibria and show that they are sparse, non-Hermitian rectangular-block
matrices modified by heterogeneous synaptic decay timescales and activation-function gains. We specify a random
matrix ensemble that faithfully captures the spectra of trained Jacobian
matrices, arising from the inhibitory core - excitatory periphery network motif (pruned E weights, broadly distributed I weights) observed post-training. An analytic theory of this ensemble is developed using statistical field theory methods: a Hermitized resolvent representation of the spectral density is processed with a supersymmetry-based treatment in the style of Fyodorov and Mirlin. In this manner, an analytic description of the spectral edge is obtained, relating statistical parameters of the Jacobians (sparsity, weight variances, E/I ratio, and the distributions of timescales and gains) to near-critical features of the
equilibria essential for robust working
memory computation.
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Statistical Mechanics
Universal splitting of phase transitions and performance optimization in driven collective systems
Gustavo A. L. Forão, Jonas Berx, Tan Van Vu et al. (+1 more)
Spontaneous
symmetry breaking is a hallmark of
equilibrium systems, typically characterized by a single critical point separating ordered and disordered phases. Recently, a novel class of non-
equilibrium phase transitions was uncovered [Phys. Rev. Res. 7, L032049 (2025)], showing that the combined effects of simultaneous contact with thermal baths at different temperatures and external driving forces can split the conventional order-disorder transition into two distinct critical points, determined by which ordered state initially dominates. We show the robustness of this phenomenon by extending a minimal interacting-
spin model from the idealized case of simultaneous bath coupling to a finite-time coupling protocol. In particular, we introduce two protocols in which the system interacts with a single bath at a time: a
stochastic protocol, where the system randomly switches between the baths at different temperatures, and a deterministic protocol where the coupling alternates periodically. Our analysis reveals two key results: (i) the splitting of phase transitions persists across all coupling schemes – simultaneous,
stochastic, and deterministic – and (ii) different optimizations of power and efficiency in a collectively operating heat engine reveal that both the
stochastic and deterministic protocols exhibit superior global performance at intermediate switching rates and periods when compared to simultaneous coupling. The global trade-off between power and efficiency is described by an expression solely depending on the temperatures of thermal reservoirs as the efficiency approaches to the ideal limit.
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All authors Gustavo A. L. Forão, Jonas Berx, Tan Van Vu, Carlos E. Fiore
Statistical Mechanics
From Frequency Dependent Specific Heat to Fictive Temperature of a Glassy Liquid
Biman Bagchi
Upon rapid quenching of temperature of a glass forming
liquid, the system falls out of
equilibrium due its finite relaxation time. Additionally, the relaxation becomes progressively slower with time. The created nonequilibrium state of the glassy system is conveniently described by introducing a fictive temperature which provides the instantaneous state of the nonequilibrium system. The fictive temperature $T_{f} (t)$ is time dependent. During cooling, the fictive temperature is higher than the actual temperature. After the cooling or quenching has ceased, the fictive temperature approaches the final temperature at a rate that depends on the relaxation properties of the
liquid. In this work we use linear response theory to connect the time dependence of the fictive temperature to
memory function which is shown to be related to the frequency dependent specific heat which itself depends on the fictive temperature $T_{f} (t)$. Thus, one requires { \it a self-consistent calculation} to capture the interdependence of relaxation rate and structural response function. We present a numerical calculation where we apply our relations to silica where the relaxation function that describes the frequency dependent specific heat and is modeled as a stretched exponential William-Watts (WW) function, while the relaxation time is modeled as a Vogel-Fulcher-Tammann (VFT). We calculate the fictive temperature self-consistently. $T_{f}(t)$ exhibits the fall out from actual temperature as time (t) progresses.
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Strongly Correlated Electrons
Basis Adaptive Algorithm for Quantum Many-Body Systems on Quantum Computers
Anutosh Biswas, Sayan Ghosh, Ritajit Majumdar et al. (+3 more)
We introduce a Basis Adaptive (BA)
algorithm for hybrid
quantum-classical simulation of correlated
quantum many-body systems. Starting from a small set of physically motivated bitstrings, the
algorithm iteratively applies a single-step first-order Trotterized
circuit on a
quantum processor, filters the sampled configurations by enforcing $U(1)$
spin conservation and
lattice reflection
symmetry, and classically diagonalizes the
Hamiltonian in the resulting reduced
Hilbert space. This design avoids the variational optimization overhead of VQE, the deep coherent
circuits required by QPE, and the
symmetry-violating subspaces that arise in SKQD. The ground-state energy error is bounded analytically by $\sqrt{8}\,\|H\|\left(1-\sqrt{\alpha_{D_T}}\right)^{1/2}$, where $\alpha_{D_T}$ is the probability weight captured by the $D_T$ sampled basis states. This bound connects
algorithm performance directly to ground-state sparsity and explains the observed accuracy hierarchy across different phases. Benchmarked on the
spin-$1/2$ Heisenberg XXZ chain (up to $N=62$
qubits on the IBM Heron processor), the
algorithm achieves a $3.5\%$ energy error in the gapped Neel phase ($\Delta=2.0$) and below $0.5\%$ at the
ferromagnetic boundary ($\Delta=-1.0$). The accuracy degrades to $28.7\%$ in the strongly quasi-long-range-ordered regime ($\Delta=0.5$).
Spin-
spin correlation functions are reproduced across all regimes, confirming that
symmetry-filtered real-time sampling provides a practical and noise-resilient pathway to ground-state properties on near-term
quantum hardware.
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All authors Anutosh Biswas, Sayan Ghosh, Ritajit Majumdar, Mostafizur Rahaman Laskar, Nicholas Bronn, Manoranjan Kumar
Mesoscale and Nanoscale Physics
Anomalous topological phases in a Chern insulator connected to leads in a cylindrical geometry
Satyam Sinha, Rekha Kumari, Junaid Majeed Bhat et al. (+3 more)
The observed robustly quantized
Hall conductance in
quantum Hall systems and Chern
insulators (CI) is normally understood in terms of the bulk
topology of isolated systems, not coupled to leads. It is assumed that the leads act as inert reservoirs. Within a model of a CI coupled to leads with a cylindrical geometry, we show that this is not always true. We identify the
Hall conductance with a boundary invariant, the winding number of the phase of the reflection coefficient. We find anomalous topological phases where the boundary invariant is not the same as the bulk Chern number, even in the limit of weak lead coupling.
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All authors Satyam Sinha, Rekha Kumari, Junaid Majeed Bhat, Abhishek Dhar, Diptiman Sen, R. Shankar
Superconductivity
Discriminating Gap Symmetries of Superconducting La$_3$Ni$_2$O$_7$
Zhan Wang, Yuxin Wang, Kun Jiang et al. (+2 more)
The discovery of high-T$_c$
superconductor in Ruddlesden-Popper nickelate materials represented by La$_3$Ni$_2$O$_7$ has opened new directions in the quest for unconventional superconductivity. A central unresolved issue concerns the pairing
symmetry of the superconducting order. In this paper, we model the superconducting order of La$_3$Ni$_2$O$_7$ using the established
Fermi surface structure together with phenomenological pairing functions belonging to $s_\pm$ and $d$-wave
symmetry classes, which are the leading possibilities in the current debate. We compute several experimentally accessible observables-including tunneling density of states, point contact spectroscopy, superfluid density, and Raman spectroscopy-each of which exhibits distinct characteristics for different gap
symmetries. These quantities provide a concrete and experimentally testable route for identifying the pairing
symmetry of La$_3$Ni$_2$O$_7$ and for clarifying the microscopic nature of nickelate superconductivity.
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All authors Zhan Wang, Yuxin Wang, Kun Jiang, Jiangping Hu, Fu-Chun Zhang
Mesoscale and Nanoscale Physics
Fast wave transport in two-dimensional $\mathcal{PT}$-symmetric lattices
Sayan Jana and Lea Sirota
We present a theoretical investigation of wave dynamics in two-dimensional non-Hermitian $\mathcal{PT}$-symmetric
lattices, where onsite, as well as inter-site control couplings are employed. Our analysis shows that these couplings can be tuned to achieve a direction-sensitive group velocity enhancement beyond what is possible in the uncontrolled (Hermitian) counterpart, while ensuring that the wave packet
evolution remains bounded and dynamically stable. We derive a dedicated relation between the control parameters, providing a systematic condition under which stability is guaranteed. We then study the topological properties of the non-Hermitian system at hand, and use an experimental-ready topoelecric metamaterial platform to demonstrate the non-Hermitian couplings realization, and the resulting wave dynamics. This framework paves the way to designing stable and fast wave transport in planar non-Hermitian media.
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Statistical Mechanics · Cross-listed from hep-th
Universal Supercritical Behavior in Global Monopole-Charged AdS Black Holes
Ankit Anand and Shoucheng Wang
We analytically investigate the Widom line and universal supercritical crossover for charged AdS black holes threaded by a global monopole. We compute thermodynamic variables in both the extended and canonical ensembles. We derive the scaled variance $\Omega$ using the Gibbs free energy and locate the Widom line as the extrema of this. Using mean-field expansion of the equation of state near criticality, we obtain closed-form expressions for the Widom line and the two branching crossover lines $L^\pm$. We show that the monopole parameter shifts the critical parameters but does not change the mean-field universal scaling: the leading linear term and the nonanalytic correction remain universal in both ensembles. We also numerically verify this using the supercritical crossover lines $L^\pm$ and show the universal scaling laws and the complete supercritical phase diagrams.
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Other Condensed Matter
Electrical Readout Strategies of GFET Biosensors for Real-World Requirements
Michael Geiwitz, Owen Rivers Page, Marina E. Nichols et al. (+5 more)
Graphene Field-Effect Transistors (GFETs) are increasingly employed as biochemical sensors due to their exceptional electronic properties, surface sensitivity, and potential for miniaturization. A critical challenge in deploying GFETs is determining the optimal electrical readout strategy. GFETs are typically operated with either of two modalities: one measuring current in real time (amperometric) and the other monitoring the change in voltage for charge neutrality (potential potentiometric). Here, we undertake a systematic study of the two modalities to determine their relative advantages/disadvantages towards guiding the future use of GFETs in sensing. We focus on viral
proteins in wastewater, given the
matrix's complexity and the growing interest in the field of wastewater surveillance. Our results show that transconductance offers far superior limits of detection (LOD) but suffers from limited reproducibility, a narrower dynamic range, and is ineffective for some viral
proteins. In comparison, we find that Dirac point tracking offers higher reproducibility and superior robustness, but at a higher LOD. Interestingly, both techniques exhibit similar sensitivity, highlighting the importance of the aptamers employed. Systematic experiments also help explain differences in dynamic range and limited functionality in detecting some
proteins, resulting from hidden electrophoresis, and shifting the high transconductance point away from the active region. Thus, our findings provide crucial considerations for designing and operating resilient
graphene biosensors suitable for real-time pathogen monitoring in environmental scenarios.
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All authors Michael Geiwitz, Owen Rivers Page, Marina E. Nichols, Tio Marello, Catherine Hoar, Deji Akinwande, Michelle M. Meyer, Kenneth S. Burch
Materials Science
Plasma engineered Hydroxyl Defects in NiO a DFTSupported-Spectroscopic Analysis of Oxygen Hole States and Implications for Water Oxidation
Harol Moreno Fernandez, Mohammad Amirabbasi, Crizaldo Jr. Mempin et al. (+8 more)
Controlling
lattice oxygen reactivity in earth abundant OER catalysts requires precise tuning of defect chemistry in the
oxide lattice. Here, we combine DFT+U calculations with
plasma assisted synthesis to show how O2 and H2O in the discharge govern vacancy formation, electronic structure, and catalytic predisposition in NiO thin films. Oxygen rich
plasmas generate isolated and clustered Ni vacancies that stabilize oxygen ligand hole states and produce shallow O 2p Ni 3d hybrid levels, enhancing Ni O covalency. In contrast, introducing H2O during growth drives local hydroxylation that compensates vacancy induced Ni3+ centers, restoring Ni2+ like coordination, suppressing deep divacancy derived in gap states, and introducing shallow Ni O H derived valence-band tails. EXAFS confirms that hydroxylation perturbs only the local environment while preserving the medium-range NiO
lattice, and Ni L-edge spectroscopy shows a persistent but redistributed ligand-hole population. These complementary vacancy and hydroxylation driven pathways provide a
plasma controlled route to pre define electronic defect landscapes in NiO and to tune its activation toward OER relevant NiOOH formation.
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All authors Harol Moreno Fernandez, Mohammad Amirabbasi, Crizaldo Jr. Mempin, Andrea Trapletti, Garlef Wartner, Marc F. Tesh, Esmaeil Adabifiroozjaei, Thokozile A. Kathyola, Carlo Castellano, Leopoldo Molina Luna, Jan P. Hofmann
Mesoscale and Nanoscale Physics
Electrically Tuneable Variability in Germanium Hole Spin Qubits
Edmondo Valvo, Michele Jakob, Patrick Del Vecchio et al. (+2 more)
Hole
spin qubits in planar germanium
heterostructures are frontrunners for scalable
semiconductor quantum computing. However, their current performance is mostly limited by large dot-to-dot variability that leads to uncontrolled
qubit energies and random tilts in the
spin quantization axis. Here, we propose a systematic and local method to engineer the
spin qubit response by imprinting a controlled anisotropy in the
quantum dot confinement, enabling on-demand electric g-tensor control. In particular, we find that both the
quantum-dot size and asymmetry allow electrical tuning of the g-tensor and significantly suppress magnitude and angular variability of the
spin response for selected
magnetic field directions. We confirm this behavior by analyzing single-disorder realizations and statistical ensembles in state-of-the-art strained and unstrained germanium channels, showing that the latter provides an optimal path for $g$-tensor engineering. Our results provide practical design principles for on-demand control of the
spin response and mitigating variability, paving the way towards large-scale germanium-based
quantum computers.
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All authors Edmondo Valvo, Michele Jakob, Patrick Del Vecchio, Maximilian Rimbach-Russ, Stefano Bosco
Quantum Gases
Probing the Crossover between Dynamical Phases with Local Correlations in a Rydberg Atom Array
Xiaofeng Wu, Xin Wang, Sixun Jia et al. (+1 more)
The experimental detection of non-
equilibrium quantum criticality remains a challenge, as traditional signatures like dynamical
quantum phase transitions rely on hard-to-measure global properties. Here, we demonstrate that local connected correlation functions provide a superior, practical means to directly probe the dynamics of
magnetic order in a quenched Rydberg atom array. Using a Magnus expansion formalism, we derive analytic expressions for these correlations that capture a smooth crossover from
antiferromagnetic to
ferromagnetic dominance. Our analytic results, which reveal the critical parameter relationship $U_{c}(\delta)$, are validated against exact numerical simulations and exhibit robustness to finite-size effects. By shifting the focus from global singularities to local correlations, our protocol establishes a direct and feasible path to observe the rich critical dynamics in scalable
quantum simulators.
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All authors Xiaofeng Wu, Xin Wang, Sixun Jia, Bo Xiong
Soft Condensed Matter
A geometric approach to predicting plasticity in disordered solids
Long-Zhou Huang, Xu Yang, Min-Qiang Jiang et al. (+2 more)
It was recently shown that
vortex-like topological defects with negative winding number in the vibrational modes of a two-dimensional glass under quasistatic shear correlate strongly with plastic events, offering a promising route to predict them. However, many of these
vortices, a number that actually grows quadratically with mode frequency, are entirely unrelated to plasticity and arise simply from the underlying plane-wave structure of the modes. This raises doubts about the fundamental relevance of such defects to plastic rearrangements and limits their predictive power. Here, we introduce a geometrical filter based on the Nye dislocation density that, when applied to the vibrational modes, removes these spurious defects and reveals the true plastic precursors. Using simulations of a two-dimensional model glass, we show that this filtered approach consistently outperforms the conventional
vortex-based method, particularly at small strains and when focusing on genuine plastic stress drops, offering a more robust tool to predicting plasticity in glasses from their undeformed initial state.
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All authors Long-Zhou Huang, Xu Yang, Min-Qiang Jiang, Yun-Jiang Wang, Matteo Baggioli
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Mid-circuit logic executed in the qubit layer of a quantum processor
Cameron Jones, Piper Wysocki, MengKe Feng et al. (+16 more)
Practical
quantum computers need to continuously exchange data between classical and
quantum subsystems during a computation. Mid-
circuit measurements of a
qubits state are transferred to the classical electronics layer, and their outcome can inform feedforward operations that close the loop back to the
quantum layer. These operations are crucial for fault-tolerant
quantum computers, but the
quantum-classical loop must be completed before the
qubits decohere, presenting a substantial engineering challenge for full-scale systems comprising millions of
qubits. Here we perform the first mid-
circuit measurements in a system of silicon
spin qubits, and show that feedforward operations can be performed without needing to route information to the classical layer. This in-layer approach leverages a backaction-driven control technique that has previously been considered a source of error. We
benchmark our in-layer strategy, together with the standard FPGA-enabled approach, and analyse the performance of both methods using gate set
tomography. Our results provide the first step towards moving resource-intensive classical processing into the
quantum layer, an advance that could solve key engineering challenges, and drastically reduce the power budget of future
quantum computers.
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All authors Cameron Jones, Piper Wysocki, MengKe Feng, Gerardo A. Paz-Silva, Corey I. Ostrove, Tuomo Tanttu, Kenneth M. Rudinger, Samuel K. Bartee, Kevin Young, Fay E. Hudson, Wee Han Lim, Nikolay V. Abrosimov, Hans-Joachim Pohl, Michael L. W. Thewalt, Robin Blume-Kohout, Andrew S. Dzurak, Andre Saraiva, Arne Laucht, Chih Hwan Yang
Disordered Systems and Neural Networks
The generalized density of states in a one-dimensional Ising model with ferrromagnetic and antiferromagnetic interactions
Boris Kryzhanovsky and Vladislav Egorov
Expressions for the density of states $D(E)$, where $D(E)$ is the number of states of energy $E$, are well known. The present paper offers the expressions for generalized density of states $D_N(E,m)$, where $D_N(E,m)$ is the number of states with energy $E$ and magnetization $m$ in a one-dimensional $N$-
spin chain. The expressions obtained here can be considered as reference ones, since all the main characteristics were obtained without them: using the transfer
matrix technique or using well-known expressions for the density of states $D(E)=\sum_m{D_N(E,m)}$. Nevertheless, the knowledge of quantity $D_N(E,m)$ helps to understand the model properties and allows the analysis of the temporal behavior of magnetization $m=m(\tau)$. In particular, we demonstrate that in a one-dimensional model spontaneous magnetization can be observed at a non-zero temperature. However, the spontaneous magnetization can randomly change its sign, which results in the magnetization averaged over a very long observation period becoming zero $\langle m(\tau)\rangle$.
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