Materials Science
Resistive switching and long-range filaments in metal/DMSO liquid systems for three-dimensional, multi-terminal connection schemes with on demand dynamic reconfigurability
Roshani Madurawala, Kerstin Meurisch, Louis Joswig et al. (+5 more)
The human
brain, with its energy-efficient and massively parallel architecture seamlessly integrates
memory and computation. Its
topology and functionality serve as the inspiration for the field of neuromorphic computing. Realizing
brain-like hardware requires the integration of fundamental properties such as synaptic plasticity, self-organization, hierarchical and modular structures, as well as three-dimensional connectivity. Current challenges lie in developing
liquid based neuromorphic material systems with facile fabrication, three-dimensional processing, and
brain-like conductivity. This work presents ionotronic systems - i.e., systems that incorporate the movement of both electrons and ions - to obtain dynamically reconfigurable conductive filaments. Our method employs an electrolyte where an anode reservoir produces ions in-situ, enabling electrode-dependent tunability and sustained operation without ion depletion. This manuscript presents four ionotronic systems. Each system grows
brain inspired three-dimensional wires contacting two or more electrodes exhibiting resistive switching at connection on a micrometer scale as well as a nanometer scale, demonstrating hierarchical organization and functionality. Furthermore, these conducting filaments are capable of being disrupted by an external electric field or dissolved over time in the ionotronic system, emulating blooming and
pruning aspects of plasticity.
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All authors Roshani Madurawala, Kerstin Meurisch, Louis Joswig, Anna Lina Wyschkon, Maik-Ivo Terasa, Sören Kaps, Alexander Vahl, Rainer Adelung
Mesoscale and Nanoscale Physics
Photonic spin Hall effect dependent on Landau level transitions in monolayer WTe2
Qiaoyun Ma, Hui Dou, Yiting Chen et al. (+2 more)
Landau level (LL) engineered photonic
spin Hall effect (PSHE) holds great promise for nanoscale manipulation and steering of magneto-optical transport in two-dimensional atomic systems. Herein, we theoretically investigate PSHE modulated by LL transitions {\delta}n = n'-n =-2, 0, +2 (where n and n' indicate the LL indexes of valence and conduction bands, respectively) in monolayer WTe2. Results show that PSHE tuned by {\delta}n =-2, 0, +2 has completely different dependent behaviors on LLs, incident angle of incident
photons, and
magnetic induction intensity. These discrepancies are ascribed to
Hall-conductivity-incurred
Hall angle {\Theta} because the variation tendency of photonic
spin Hall shifts is similar to that of {\Theta} with changing the LL index.
Giant PSHE with the largest in-plane displacement of more than 400 times of incident wavelength is obtained at the transition |n=55>->|n'=57>. Remarkably enhanced PSHE occurs at near-zero
Hall angles. In-plane and transverse
spin-dependent displacements give their respective extremum values at the same incident angles when the {\Theta} is near to zero, and their incident-angle deviation will become larger and larger as the |{\Theta}| increases. This unambiguously confirms the strong influence of
Hall angle in the PSHE, shedding important insights into the fundamental properties of
spin-orbit interaction of light in time-reversal
symmetry breaking
quantum systems.
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All authors Qiaoyun Ma, Hui Dou, Yiting Chen, Guangyi Jia, Xinxing Zhou
Disordered Systems and Neural Networks
Stochastic Dynamics of Skyrmions on a Racetrack: Impact of Equilibrium and Nonequilibrium Noise
Anton V. Hlushchenko, Mykhailo I. Bratchenko and Aleksei V. Chechkin
Current-driven motion of domain walls and skyrmions is central to the operation of non-volatile
magnetic memory devices. Racetrack
memory requires current densities high enough to generate velocities above 50 m/s, but such conditions also enhance
spin-current noise. We develop a theoretical framework based on the
stochastic Thiele equation to analyze the effects of
equilibrium (thermal) and nonequilibrium (
spin-current) fluctuations on skyrmion dynamics. From this approach, we derive
diffusion coefficients and mean-squared displacements that quantify
stochastic motion under both noise sources. Micromagnetic simulations and analytical results demonstrate that
spin-current noise dominates skyrmion dynamics in typical racetrack structures up to room temperature. We further address the first-passage-time problem, obtaining the mean first-passage time and its standard deviation along and across the racetrack. These results quantify how random displacements affect skyrmion propagation and detection, providing insights into error sources in high-speed racetrack
memory devices.
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Materials Science
Excitonic optical interface for GHz-THz collective excitations in a van der Waals magnet
Sophie Bork, Richard Leven, Vincent Wirsdörfer et al. (+9 more)
Collective
spin and
lattice excitations in
quantum materials span energy scales from GHz to THz, yet establishing a unified optical interface for these modes remains a central challenge. Here we show that excitonic resonances in the van der Waals antiferromagnet CrSBr provide a broadband optical interface for such excitations. Using femtosecond broadband transient reflectivity, we resolve coherent GHz
magnon and THz
phonon modes that modulate the dielectric response over a wide spectral range. Despite their distinct microscopic origin and frequency scales, both excitations give rise to the same emergent optical signature: a resonance at 1.46 eV that is absent in steady-state spectra and exhibits a characteristic {\pi}-phase inversion, identifying it as a discrete excitonic transition. We attribute this behaviour to
boson-driven modulation of the dielectric response, which transiently transfers spectral weight from a nominally dark
exciton into an observable channel without requiring a finite
equilibrium oscillator strength. Supported by many-body calculations, we assign this feature to a higher-energy
exciton with distinct momentum and orbital character and strongly suppressed optical
matrix elements. These results establish excitonic resonances in van der Waals magnets as a platform for interfacing collective excitations across GHz, THz and optical frequency scales.
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All authors Sophie Bork, Richard Leven, Vincent Wirsdörfer, Alessandro Ferretti, Rafael R. Rojas-Lopez, Mattia Benini, David Maximilian Janas, Umut Parlak, Alberto Brambilla, Alexey V. Scherbakov, Swagata Acharya, Mirko Cinchetti
Superconductivity
Ta-based Josephson junctions using insulating ALD TaN tunnel barriers
Ekta Bhatia, Jack Lombardi, Tuan Vo et al. (+16 more)
Josephson junctions form the core
circuit element in superconducting
quantum computing
circuits, single flux
quantum digital logic
circuits, and sensing devices such as SQUIDs. Aluminum
oxide has typically been used as the tunnel barrier. Its formation by exposure to low oxygen pressures at room temperature for short periods of time makes it susceptible to aging and limits the thermal budget of downstream processes. In this paper, we report the first demonstration of {\alpha}-Ta/insulating TaN/a-Ta
superconductor/
insulator/
superconductor Josephson junctions fabricated on 300 mm wafers using CMOS-compatible processes. The junctions were fabricated on high-resistivity silicon substrates using standard processes available at 300 mm scale, including 193 nm optical lithography, ALD of TaN in a cluster tool, and chemical mechanical planarization to enable highly planar interfaces. Junction areas ranging from 0.03 um2 to 9 um2 with ALD TaN thickness between 2 nm and 7 nm were characterized. A critical current density of 76 uA/um2 was observed in junctions using 4 nm ALD TaN in the tunnel barrier. The dependence of Jc on ALD TaN layer thickness is analyzed, and the influence of junction geometry, packaging, and temperature on I-V characteristics is discussed. Junctions were retested after a period of 4 months to quantify junction aging. The potential of this novel material system and a 300 mm superconducting junction process flow to fabricate thermally and environmentally stable junctions is discussed. The
vision of a Superconducting
Quantum Process Design Kit for a Multi-Project Wafer program to enable rapid development and proliferation of superconducting
quantum and digital digital logic systems is presented. This work represents the first step towards establishing such a
Quantum Foundry, providing access to high quality
qubits and single-flux
quantum logic
circuits at 300 mm wafer scale.
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All authors Ekta Bhatia, Jack Lombardi, Tuan Vo, Michael Senatore, Alexander Madden, Soumen Kar, Hunter Frost, Stephen Olson, Jakub Nalaskowski, John Mucci, Brian Martinick, Ilyssa Wells, Thomas Murray, Kevin Musick, Corbet S. Johnson, Stephen McCoy, Daniel L. Campbell, Matthew D. LaHaye, Satyavolu S. Papa Rao
Strongly Correlated Electrons
Xiang Li, Xiangjian Qian and Mingpu Qin
In this work, we investigate the Kitaev honeycomb model employing the recently developed Clifford
Circuits Augmented
Matrix Product States (CAMPS) method. While the model in the gapped phase is known to reduce to the toric code model - whose ground state is entirely constructible from Clifford
circuits - we demonstrate that the very different gapless
quantum spin liquid (QSL) phase can also be significantly disentangled with Clifford
circuits. Specifically, CAMPS simulations reveal that approximately two-thirds of the
entanglement entropy in the isotropic point arises from Clifford-
circuit contributions, enabling dramatically more efficient computations compared to conventional
matrix product state (MPS) methods. Crucially, this finding implies that the Kitaev QSL state retains significant Clifford-simulatable structure, even in the gapless phase with non-abelian anyon excitations when time reversal
symmetry is broken. This property not only enhances classical simulation efficiency significantly but also suggests substantial resource reduction for preparing such states on
quantum devices. As an application, we leverage CAMPS to study the Kitaev-Heisenberg model and determine the most accurate phase boundary between the anti-
ferromagnetic phase and the Kitaev QSL phase in the model. Our results highlight how Clifford
circuits can effectively disentangle the intricate
entanglement of Kitaev QSLs, opening avenues for efficiently simulating related and similar strongly correlated models.
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Mesoscale and Nanoscale Physics
Escaping AB caging via Floquet engineering: photo-induced long-range interference in an all-band-flat model
Aamna Ahmed, Mónica Benito and Beatriz Pérez-González
Flat-band
lattices hosting compact localized states are highly sensitive to external modulation, and the tailored design of a perturbation to imprint specific features becomes relevant. Here we show that periodic driving in the high-frequency regime transforms the all-flat-band diamond chain into one featuring two tunable quasi-flat bands and a residual flat band pinned at $E=0$. The interplay between
lattice geometry and the
symmetries of the driven system gives rise to drive-induced tunneling processes that redefine the interference conditions and open a controllable route to escaping Aharonov-Bohm caging. Under driving, the diamond chain effectively acquires the geometry of a dimerized
lattice, exhibiting charge oscillations between opposite boundaries. This feature can be exploited to generate two-particle
entanglement that is directly accessible experimentally. The resulting drive-engineered quasi-flat bands thus provide a versatile platform for manipulating
quantum correlations, revealing a direct link between spectral fine structure and dynamical
entanglement.
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Statistical Mechanics · Cross-listed from physics.flu-dyn
Numerical Simulation of the Cleaning Process of Microchannel by an External Flow
Boris S. Maryshev and Lyudmila S. Klimenko
This paper describes the problem of drift of solid non-interacting particles in a microchannel, which can stick to its walls under the action of the van der Waals forces and break away from the wall due to thermal noise and viscous stresses arising from the flow. The pressure drop is given between the channel inlet and outlet. At the initial moment of time, the channel walls are contaminated with adhered particles, i.e. the walls are uneven, which affects the formation of the flow structure through the channel. Over time, under the action of viscous stresses and thermal noise, the particles break away from the channel walls, causing its cleaning. The interaction of the detached particles with the flow is taken into account in the Stokes approximation. In addition, the model takes into account random particle motion caused by
diffusion. The problem is solved numerically within the framework of the random walk model. The
evolution of the
liquid flow in the channel during its cleaning is obtained: stream function, pressure, and vorticity fields. The dependencies of the volume occupied by settled particles, the flow rate through the channel and the channel gap on time are determined for different values of the interaction force between particles and channel wall. The estimations of the channel cleaning time are obtained and discussed. The possibility of control the cleaning process by the modulation of
liquid flux through the channel is investigated. It is shown that resonance phenomena can be observed. The dependencies of cleaning time on the modulation amplitude and frequency is obtained and studied. It is shown that changing the modulation parameters leads to a significant change in the cleaning time and helps control the cleaning process.
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Mesoscale and Nanoscale Physics
Nonlinear Hall responses in tunable nodal Dirac semimetals
Akash Dey
We investigate the nonlinear
Hall responses in tunable two-dimensional Dirac materials. In particular, we study
quantum geometry-driven second and third-order nonlinear responses in a time-reversal symmetric Dirac semimetal that can host single-node, double-node, and nodal-ring depending on the model parameters. We find that the second-order
Hall (SOH) response, which originates from the Berry
curvature dipole, is enhanced in the single-node semimetallic phase as compared to the double-node case when inversion
symmetry is broken. In contrast, the SOH response vanishes in the nodal-ring semimetal as the inversion
symmetry is retained. Notably, the third-order
Hall response due to Berry connection polarizability becomes much larger in the nodal-ring Dirac semimetal, especially when the
Fermi energy lies near the band edge, than in the single- and double-node Dirac semimetals. The reason for this contrasting behavior is attributed to the distinct distribution of the Berry connection polarizability in the Brillouin zone.
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Materials Science
Drastic reduction of the slow scintillation component in highly luminescent Ce3+ and Mg2+ doped Lu2.5Gd0.5Ga2Al3O12 garnet powders
Lenka Prouzová Procházková, Eliška MÜllerová, Jan Bárta et al. (+4 more)
This paper deals with the photochemical preparation of nanomaterials with garnet structure. Ce3+ and Mg2+ doped Lu2.5Gd0.5Ga2Al3O12 powders were prepared by using UV irradiation of aqueous solutions with low-pressure mercury lamps and subsequent calcination of the solid products. The synthesis was optimized and gives access to a range of doping which is very hard to achieve with single
crystal growth from melt. The effect of Ce and Mg concentration on the structural and luminescence properties was studied. Garnets were analyzed using X-ray fluorescence (XRF) and X-ray powder diffraction (XRPD) and their luminescence properties under optical and X-ray
photon excitations were investigated. XRF and XRD show that the samples are sufficiently chemically pure and phase-pure and their elemental composition corresponds with expectations.
Laser-induced breakdown spectroscopy confirmed that Mg concentrations in Mg-codoped samples are slightly lower than the nominal. Luminescence spectra show typical emission maxima of 5d-4f Ce3+ transition and 4f-4f Gd3+ transition. The effects of the concentration of Ce3+ and Mg2+ on the RL intensity, light yields and decays were observed.
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All authors Lenka Prouzová Procházková, Eliška MÜllerová, Jan Bárta, Estelle Homeyer, Alena Zavadilová, Christophe Dujardin, Václav čuba
Materials Science
High-pressure melting and elastic behavior of vanadium and niobium based on ab initio and machine learning molecular dynamics
Hao Wang, Dan Wang, Long Hao et al. (+2 more)
Under high pressure, the group-VB transition metals vanadium (V) and niobium (Nb) exhibit simple
crystal structures but complex physical behaviors, such as anomalous compression-induced softening and heating-induced hardening (CISHIH). Meanwhile, the impact of
lattice thermal expansion-induced softening at elevated temperatures on HIH is yet to be investigated. Therefore, this study utilized ab initio (AIMD) and machine learning molecular dynamics (MLMD) to investigate the melting and abnormal mechanical softening-hardening behaviors of V and Nb under high pressure. Simulations reveal that the high-temperature Pnma phase of Nb reported in previous experimental studies is highly susceptible to mechanical instability and reverts to the body-centered cubic (BCC) phase. This discovery prompted a revised determination of the high-pressure melting line of Nb. The melting temperature of Nb significantly exceeds the existing theoretical and experimental estimate compared with that of V. AIMD simulations demonstrate that atomic thermal displacements have a greater influence on the HIH of V and Nb than pure electron temperature effects. In addition, the temperature-dependent anomalous elastic properties of V and Nb were investigated within a pressure range of 0-250 GPa using MLMD. The mechanical properties of V and Nb transitioned from HIH to heating-induced softening, elucidating the competition between thermal-expansion-induced softening and HIH. This study advances fundamental understanding of V and Nb physics, providing crucial theoretical foundations for establishing accurate equations of state and constitutive models for these metals.
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All authors Hao Wang, Dan Wang, Long Hao, Jun Li, Hua Y. Geng
Mesoscale and Nanoscale Physics
Microwave spectroscopy of few-carrier states in bilayer graphene quantum dots
Max J. Ruckriegel, Christoph Adam, Rebecca Bolt et al. (+8 more)
Bilayer graphene is a maturing material platform for gate-defined
quantum dots that hosts long-lived
spin and valley states. Implementing solid-state
qubits in
bilayer graphene requires a fundamental understanding of such confined electronic systems. In particular, states of two and three carriers, for which the exchange interaction between particles plays a crucial role, are a cornerstone for
qubit readout and manipulation. Here we report on the spectroscopy of few-carrier states in
bilayer graphene quantum dots, using
circuit quantum electrodynamics (cQED) techniques that offer substantially improved energy resolution compared to standard transport techniques. Measurements using a superconducting high-impedance resonator capacitively coupled to the double
quantum dot reveal dispersive features of two and three electron states, enabling the detection of Pauli
spin and valley blockade and the characterization of the
spin-orbit gap at zero
magnetic field. The results deepen our understanding of few-carrier
spin and valley states in
bilayer graphene quantum dots and demonstrate that cQED techniques are a powerful state-selective probe for
semiconductor nanostructures.
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All authors Max J. Ruckriegel, Christoph Adam, Rebecca Bolt, Chuyao Tong, David Kealhofer, Artem O. Denisov, Mohsen Bahrami Panah, Kenji Watanabe, Takashi Taniguchi, Thomas Ihn, Klaus Ensslin
Disordered Systems and Neural Networks · Cross-listed from physics.optics
Largest eigenvalue statistics of wavefront shaping in complex scattering media
Grégory Schehr and Hasan Y{\i}lmaz
In wavefront shaping, light, sound, and other waves are focused through complex scattering media onto one or more target positions, and the resulting intensity enhancement is quantified by the enhancement factor. While reproducible enhancement is crucial in experiments, the fluctuations of the enhancement factor remain largely unexplored. Here, we combine experiments, numerical simulations, and exact random-
matrix theory to determine its full distribution for multi-target focusing. Exact finite-size random-
matrix predictions accurately describe both the mean enhancement factor and its fluctuations beyond the asymptotic Marčenko-Pastur regime, whenever long-range mesoscopic correlations are negligible (e.g., in weakly scattering media or when only a limited number of input channels is controlled). In contrast, strongly scattering media exhibit
giant enhancement-factor fluctuations that increasingly exceed these parameter-free predictions as the number of controlled input channels increases. These findings establish the enhancement factor not only as a measure of focusing performance, but also as a sensitive statistical observable that provides a simple and experimentally accessible probe of long-range mesoscopic correlations.
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Statistical Mechanics
On the nature of the spin glass transition
Gesualdo Delfino
We recently showed that the two-dimensional Ising
spin glass allows for a line of renormalization group fixed points which explains properties observed in numerical studies. We observe that this exact result corresponds to enhancement to a one-generator continuous internal
symmetry. This finally explains why no finite temperature transition to a
spin glass phase is observed in two dimensions. In more than two dimensions, instead, the continuous
symmetry can be broken spontaneously and yields a
spin glass order parameter which, for fixed temperature and disorder strength, takes continuous values in an interval. Such a feature is shared by the order parameter of the known mean field solution of the model with infinite-range interactions, which corresponds to infinitely many dimensions.
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Soft Condensed Matter
Noninvasive rheological inference from stable flows in confined tissues
Marc Karnat, Gautham Hari Narayana, Sudheer Kumar Peneti et al. (+8 more)
Quantifying the in-plane rheology of epithelial monolayers remains challenging due to the difficulty of imposing controlled shear. We introduce a self-driven, rheometer-like assay in which collective migration generates stationary shear flows, allowing rheological parameters to be inferred directly from image sequences. The assay relies on two sets of ring-shaped fibronectin patches, micropatterned in arrays for high-throughput imaging. Within isolated rings, the epithelial tissue exhibits persistent rotation, from which we infer active migration stresses and substrate friction. Within partially overlapping rings, the tissue exhibits sustained shear, from which we infer the elastic and viscous responses of the
cells. The emergence of a Maxwell-like viscoelastic relation – characterized by a linear relationship between mean
cell deformation and neighbor-exchange rate – is specifically recapitulated within a wet vertex-model framework, which reproduces experimental measurements only when intercellular viscous dissipation is included alongside substrate friction. We apply our method to discriminate the respective roles of two myosin~II isoforms in tissue mechanics. Overall, by harnessing self-generated stresses instead of externally imposed ones, we propose a noninvasive route to rheological inference in migrating epithelial tissues and, more generally, in actively flowing granular materials.
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All authors Marc Karnat, Gautham Hari Narayana, Sudheer Kumar Peneti, Victoria Guglielmotti, Qazi Saaheelur Rahaman, Shreyansh Jain, Benoît Ladoux, Shao-Zhen Lin, Sham Tlili, René-Marc Mège, Jean-François Rupprecht
Mesoscale and Nanoscale Physics
Valley physics in the two bands $\mathbf{k}\cdot\mathbf{p}$ model for SiGe heterostructures and spin qubits
Tancredi Salamone, Biel Martinez Diaz, Jing Li et al. (+2 more)
We discuss the choice and implementation of inter-valley potentials in the so-called two bands $\mathbf{k}\cdot\mathbf{p}$ model for the opposite $X$, $Y$ or $Z$ valleys of silicon. We focus on the description of valley splittings in Si/SiGe
heterostructures for
spin qubits, with a particular
attention to
alloy disorder. We demonstrate that the two bands $\mathbf{k}\cdot\mathbf{p}$ model reproduces the valley splittings of atomistic tight-binding calculations in relevant
heterostructures (SiGe spikes, wiggle wells...), yet at a much lower cost. We show that the model also captures the effects of valley-orbit mixing and yields the correct inter-valley dipole
matrix elements that characterize manipulation, dephasing and relaxation in
spin/valley
qubits. We simulate a realistic Si/SiGe
spin qubit device as an illustration, and discuss electron-
phonon interactions in the two bands $\mathbf{k}\cdot\mathbf{p}$ model. Beyond
spin qubits, this model enables efficient simulations of SiGe
heterostructure devices where
spin and valley physics are relevant.
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All authors Tancredi Salamone, Biel Martinez Diaz, Jing Li, Lukas Cvitkovich, Yann-Michel Niquet
Materials Science
Structural evolution of iron oxides melts at Earth's outer-core pressures
Céline Crépisson, Mila Fitzgerald, Domenic Peake et al. (+32 more)
Oxygen and other light elements comprise up to 5 wt% of the Earth's outer-core, and may significantly influence its physical properties and the operation of the geodynamo. Here we report in situ x-ray diffraction measurements of Fe, Fe + 4.5 FeO (atomic proportion), and Fe2O3 melts at 177-438 GPa, achieved using
laser-driven shock compression at an x-ray free-electron
laser. The melts exhibit Fe-O coordination numbers between 4.0(0.4) and 4.5(0.4), indicating predominantly four-fold coordination environments. These coordination states are significantly smaller than those of Fe-bearing lower-mantle phases such as bridgmanite and ferropericlase. Shorter Fe-Fe interatomic distances in compressed iron
oxide melts drive the denser packing relative to ambient melts, while the structural differences between Fe + 4.5 FeO and Fe2O3 melts under shock indicate that the oxidation state modulates oxygen solubility in
liquid Fe. At around 177 GPa (380 km below the core-mantle boundary), Fe2O3 melts exhibit higher Fe-O coordination, suggesting that local variations in oxygen content could contribute to the stratification in the uppermost outer-core inferred from seismological and geomagnetic observations.
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All authors Céline Crépisson, Mila Fitzgerald, Domenic Peake, Patrick Heighway, Thomas Stevens, Adrien Descamps, David McGonegle, Alexis Amouretti, Karim K. Alaa El-Din, Michal Andrzejewski, Sam Azadi, Erik Brambrink, Carolina Camarda, David A. Chin, Samuele Di Dio Cafiso, Ana Coutinho Dutra, Hauke Höppner, Kohdai Yamamoto, Zuzana Konôpkovà, Motoaki Nakatsutsumi, Norimasa Ozaki, Danae N. Polsin, Jan-Patrick Schwinkendorf, Georgiy Shoulga, Cornelius Strohm, Minxue Tang, Harry Taylor, Monika Toncian, Yizhen Wang, Jin Yao, Gianluca Gregori, Justin S. Wark, Karen Appel, Marion Harmand, Sam M. Vinko
Mesoscale and Nanoscale Physics
Conservation in High-field Quantum Transport
Mukunda P. Das and Frederick Green
We give a short overview of the role of microscopic conservation in charge transport at small scales, and at driving fields beyond the linear-response limit. As a practical example we recall the measurement and theory of interband coupling effects in a
quantum point contact driven far from
equilibrium.
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Soft Condensed Matter
Comparing the Mechanical and Thermodynamic Definitions of Pressure in Ice Nucleation
Pablo Montero de Hijes, Kaihang Shi, Carlos Vega et al. (+1 more)
Crystal nucleation studies using hard-sphere and Lennard-Jones models have shown that the pressure within the
nucleus is lower than that in the surrounding
liquid. Here, we use the mechanical route to obtain it for an ice
nucleus in supercooled water (TIP4P/Ice) at 1 bar and 247 K. From this (mechanical) pressure, we obtain the interfacial stress using a thermodynamic definition consistent with mechanical arguments. This pressure is compared with that of bulk ice at equal chemical potential (thermodynamic pressure), and the interfacial stress with the interfacial free energy. Furthermore, we investigate these properties on the basal plane. We find that, unlike in hard-sphere and Lennard-Jones systems, mechanical and thermodynamic pressures agree for the
nucleus, and the interfacial stress and free energy are comparable. Yet the basal interface displays an interfacial stress nearly twice its interfacial free energy, suggesting that this agreement may be system dependent, underscoring the limitations of mechanical routes to solid-
liquid interfacial free energies.
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All authors Pablo Montero de Hijes, Kaihang Shi, Carlos Vega, Christoph Dellago
Materials Science
Photoluminescence Quenching in WSe$_2$ via p-Doping Induced by Functionalized Rylene Dyes
Ana M. Valencia, Theresa Kuechle, Maximiliam Tomoscheit et al. (+6 more)
Hybrid
heterostructures combining transition metal dichalcogenides (TMDs) with light-harvesting dyes are promising materials for next-generation optoelectronics. Yet, controlling and understanding interfacial charge transfer mechanisms in these complex systems remains a major challenge. Here, we investigate the microscopic origin of photoluminescence (PL) quenching in $\text{WSe}_2$ functionalized with a novel, strongly electron-deficient perylene monoimide dye, $\text{CN}_4\text{PMI}$. Experimentally, the hybridization induces a $\sim$97% PL quenching in $\text{WSe}_2$, confirming substantial static charge transfer and increased $p$-doping from the dye. To isolate the dominant electronic mechanism, we investigate from first principles various interface morphologies, including differing molecular orientations and layer thicknesses. Our density-functional theory results confirm that $\text{CN}_4\text{PMI}$ acts as a strong electron acceptor, inducing $p$-doping and forming a type-II level
alignment with all considered configurations, giving rise to a small or vanishing band gap. Based on these findings, we attribute the observed PL suppression in $\text{WSe}_2$ to these strong electronic interactions with the dye. Our study provides a clear and validated strategy for tailoring the electronic structure of TMDs through targeted, electron-deficient organic functionalization.
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All authors Ana M. Valencia, Theresa Kuechle, Maximiliam Tomoscheit, Sarah Jasmin Finkelmeyer, Olga Utismenko, Kalina Peneva, Martin Presselt, Giancarlo Soavi, Caterina Cocchi
Soft Condensed Matter
How elasticity affects bubble pinch-off
Coen I. Verschuur, Alexandros T. Oratis, Vatsal Sanjay et al. (+1 more)
The pinch-off of bubbles in viscoelastic
liquids is a fundamental process that has received little
attention compared to viscoelastic drop pinch-off. While these processes exhibit qualitative similarities, the dynamics of the pinch-off process are significantly different. When a drop of a dilute
polymer solution pinches off, a thread is known to develop that prevents breakup due the diverging
polymer stresses. Conversely, our experiments reveal that this thread is absent for bubble pinch-off in dilute
polymer solutions. We show that a thread becomes apparent only for high
polymer concentrations, where the pinch-off dynamics become very sensitive to the size of the needle from which the bubble detaches. The experiments are complemented by numerical simulations and analytical modeling using the Oldroyd-B model, which capture the dilute regime. The model shows that
polymer stresses are still singular during bubble pinch-off, but the divergence is much weaker as compared to drop pinch-off. This explains why, in contrast to droplets, viscoelastic bubble-threads do not appear for dilute suspensions but require large
polymer concentrations
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All authors Coen I. Verschuur, Alexandros T. Oratis, Vatsal Sanjay, Jacco H. Snoeijer
Strongly Correlated Electrons
Finite-temperature stability of skyrmion crystals in frustrated magnets: Role of sixfold anisotropy and uniform spin mode in momentum space
Kazuki Okigami and Satoru Hayami
We study the finite-temperature stability of skyrmion
crystals in frustrated magnets by analyzing the momentum-space exchange interaction of a classical Heisenberg model on a triangular
lattice. Our analysis identifies two key momentum-space features that play a crucial role in stabilizing the skyrmion
crystal phase. The first is the sixfold anisotropy in the momentum-space exchange interaction, which acts as a locking potential favoring triple-$Q$ skyrmion
crystals. Monte Carlo simulations reveal that a larger anisotropy tends to enhance the stability region of the skyrmion
crystal in the temperature–
magnetic-field phase diagram. The second factor is the momentum-space energy related to the uniform
spin mode, which correlates with the emergence of the skyrmion
crystal phase at finite temperatures. These results provide a further understanding of the stabilization mechanism of the skyrmion
crystal phase in frustrated magnets and will be useful for the design of skyrmion-hosting materials.
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Superconductivity
Percolative Pathway to Stripe Order in KTaO3-Based Superconductivity
Zhihao Chen, Chun Sum Brian Pang, Meng Yang et al. (+8 more)
The sensitivity of low dimensional
superconductors to fluctuations gives rise to emergent behaviors beyond the conventional Bardeen Cooper Schrieffer framework. Anisotropy is one such manifestation, often linked to spatially modulated electronic states and unconventional pairing mechanisms. Pronounced in plane anisotropy recently reported at KTaO3 based
oxide interfaces points to the emergence of a stripe order in superconducting phase, yet its microscopic origin and formation pathway remain unresolved. Here, we show that controlled interfacial disorder in MgO/KTaO3(111)
heterostructures drives a percolative
evolution from localized Cooper-pair islands to superconducting puddles and eventually to stripes. The extracted stripe width matches the
spin precession length, suggesting a self organized modulation governed by
spin orbit coupling and
lattice-
symmetry breaking. These findings identify disorder as both a tuning parameter and a diagnostic probe for emergent superconductivity in two dimensional
quantum materials.
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All authors Zhihao Chen, Chun Sum Brian Pang, Meng Yang, Yuxin Wang, Kun Jiang, Bruce A. Davidson, Ilya Elfimov, George A. Sawatzky, Andrea Damascelli, Ke Zou, Zhi Gang Cheng
Materials Science
Unusual Thermally Induced Blueshift and Emission Amplification of Mn2+ ions Enable Filter-Free Luminescent Thermal Imaging
Y. Abe, M. Szymczak, J. Zeler et al. (+1 more)
The shift from point-based thermal sensing to filter-free thermal imaging requires luminescent thermometers that exhibit pronounced and thermally driven spectral changes within spectral regions matching the sensitivity profiles of the R, G, and B channels of a digital camera. In this work, we introduce such a system, enabled by the synergistic interplay between (i) thermal redistribution among the vibronic components of the 4T1 excited state of Mn2+ ions and (ii) thermally assisted population of this state via optical trap sites. These combined processes result in a simultaneous thermal enhancement and blueshift of the Mn2+ emission band associated with the 4T1 -> 6A1 electronic transition. Consequently, the emission intensity recorded in the G channel increases with temperature, while the luminescence signals detected in the B channel exhibit a corresponding decrease. As demonstrated, Ca19Zn2(PO4)14:Mn2+, Ce3+ supports not only sensitive filter-free thermal imaging, but also two additional ratiometric readout schemes: one based on the intensity ratio of Ce3+ and Mn2+ emissions, and another based on two distinct spectral regions of the Mn2+ emission band, yielding maximum relative sensitivities of 0.42% K^-1 and 2.7% K^-1, respectively. This approach introduces a unique thermometric strategy that enables simple, robust, and cost-effective two-dimensional thermal imaging without the need for optical filters or specialized instrumentation.
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All authors Y. Abe, M. Szymczak, J. Zeler, L. Marciniak
Materials Science
Phase Field Study of Exchange Coupling of Hard/Soft Ferrite on Magnetic Permeability
Xinyu Xu, Wenqin Yue, Yueli Yu et al. (+2 more)
Effective modulation of
magnetic permeability plays a vital role in the development of high-performance inductors. Here, phase-field simulations of hard/soft ferrite composites (BaM/NiZn) clarify how exchange coupling and microstructure impact
magnetic permeability. We show that particle size, volume fraction, and orientation of the hard phase can effectively control the transition from collinear to non-collinear coupling, with a critical exchange size r_cr approximately 12 nm. Increasing the hard-phase fraction deepens the anisotropy energy well and monotonically suppresses permeability. In contrast, rotating the BaM easy axis to 90 degrees relative to the applied field produces a strong enhancement: at a 10 nm radius and eta = 0.1 volume fraction, the effective permeability can be more than 30 times larger than in the parallel configuration and then saturates for larger particles. This study establishes a microstructure-permeability-based physical framework for designing hard/soft
magnetic composite systems.
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All authors Xinyu Xu, Wenqin Yue, Yueli Yu, Yongke Yan, Liwei D. Geng
Statistical Mechanics
A Single–Index Theory of Optimal Branching: Murray Laws, Gilbert Networks, and Young–Herring Junctions
Justin Bennett
Murray-type flux-radius laws, Gilbert-type concave transport costs, and Young-Herring triple-junction angle balances are usually treated as separate theories. This work shows that, within a natural class of quadratic, scale-free ledgers for branched networks, all three are different faces of a single structure controlled by one dimensionless index chi. Each edge carries a flux Q, an effective radius r, and a per-length ledger P(Q,r) encoding transport dissipation and structural burden. Under locality, evenness in Q, linear-response (quadratic) dependence, and an exact homogeneity ansatz in (Q,r), any admissible ledger reduces in the scale-free regime to the two-term form P(Q,r) = a Q^2 r^{-p} + b r^m. Local optimality then implies simultaneously: (i) a flux-radius power law with generalized Murray closures at degree-3 nodes; (ii) a Young-Herring-type vector balance with radius weights r^m and a fixed symmetric Y-junction angle; and (iii) an effective flux-only cost of Gilbert/branched-transport type with exponent beta. The exponents alpha and beta, the symmetric angle, and the split between transport and structural cost are all set by chi = m/(m+p) = beta/2. A
rigidity theorem shows conversely that any quadratic ledger that yields power-law optimal radii and power-law flux-only cost on an open scaling cone must belong to this two-term family and obey the same Murray-Gilbert-Young dictionary. Examples for Poiseuille, diffusive, and geophysical trees illustrate how chi can be inferred from geometry and used as a falsifiable order parameter for scale-free branching architectures.
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Soft Condensed Matter · Cross-listed from physics.flu-dyn
Probing superhydrophobic surface topography using droplet adhesion
Pawan Kumar, Marta Krasowska and Joseph D. Berry
Understanding contact line dynamics on superhydrophobic surfaces with microscopic structures is essential for designing materials with reduced drag, anti-icing, self-cleaning, and anti-fouling properties. Using numerical simulations, we demonstrate that forces on droplets receding over structured surfaces are governed by microscale deformations near the contact line. We present and experimentally validate an expression demonstrating that adhesion force increases logarithmically with pillar area fraction at constant droplet volume and pillar surface chemistry. Furthermore, we establish that the average tensile force measured in direct force measurements provides a more reliable indicator of surface structure than the commonly used maximum force. This newfound insight enables precise quantification of superhydrophobic surface structure using a droplet probe.
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Soft Condensed Matter · Cross-listed from physics.flu-dyn
Simulating droplet adhesion on superhydrophobic surfaces
Pawan Kumar and Joseph D. Berry
A numerical model is proposed to simulate the adhesion, compression, and subsequent detachment of a micro-liter droplet from a superhydrophobic surface composed of chemically homogeneous pillars arranged in a periodic fashion, replicating a typical force probe microscopy experiment. We observe that as the droplet is pulled away from the surface, the net vertical force varies in a typical sawtooth manner with peculiar peaks and troughs, characteristic of the surface. The force first reaches a maximum before the droplet detaches from the surface with a comparatively lower force. The force variation predicted by the numerical model is in good agreement with the experimental results of Kumar et al. [1]. We also studied the effect of evaporation on the variation in the adhesion force by simulating an evaporating droplet on a superhydrophobic surface. For an evaporating droplet, the numerically predicted maximum and detachment force magnitudes are in good agreement with those obtained experimentally when we take into account the change in the droplet weight as it evaporates. The proposed method will be useful for the quantitative analysis and design of a variety of superhydrophobic surfaces and will pave the way for more accurate surface characterization based on droplet adhesion force measurements.
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Superconductivity
Visualization of Current-Driven Vortex Formation in High-$T_c$ Cuprate Superconductors
Shunsuke Nishimura, Takeyuki Tsuji, Takayuki Iwasaki et al. (+3 more)
Type-II
superconductors exhibit hysteretic behavior due to the presence of
quantum vortices, and the order in which temperature and external field are varied plays a decisive role. Here we take current, rather than
magnetic field, as the external drive. We image the
magnetic field of a high-$T_c$ cuprate
superconductor strip after cooling. We confirm that even in zero
magnetic field, current-biased cooling nucleates
vortices within the strip. With a small external
magnetic field, the distribution is polarized opposite to the Lorentz-force direction. These behaviors follow from the self-consistent relation between current and local field in steady flux flow. Our findings show that current history is encoded as
vortices. This reveals self-field effects that influence dc measurements and glassy transitions under drive.
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All authors Shunsuke Nishimura, Takeyuki Tsuji, Takayuki Iwasaki, Mutsuko Hatano, Kento Sasaki, Kensuke Kobayashi
Materials Science
Pseudopotentials for Orbital-Free DFT: Capturing Nonlocality and Correcting Functional Approximants
Valeria Rios-Vargas, Ezekiel Oyeniyi, Xuecheng Shao et al. (+4 more)
Developing reliable pseudopotentials for orbital-free density functional theory (OF-DFT), especially for transition metals, remains a significant challenge. In this study, we provide a theoretical framework for analyzing pseudization strategies for OF-DFT calculations. From the analysis arises a proposed pseudization method which involves constructing local pseudopotentials by targeting existing Kohn-Sham DFT pseudopotentials through an optimized effective potential procedure. We produce four distinct sets of local pseudopotentials and evaluate their accuracy and transferability on the transition metal elements. Our results indicate a substantial improvement over previously available pseudopotentials. Although current OF-DFT functionals still only reach a qualitative accuracy for transition metals, our newly developed pseudopotentials provide a rigorous framework for further methodological advancements.
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All authors Valeria Rios-Vargas, Ezekiel Oyeniyi, Xuecheng Shao, Wala Fathelrahman Ibrahim Elsayed, Sunday Joseph Ogenyi, Alex Okello, Michele Pavanello