Materials Science
Molecular ink-based synthesis of Bi(SzSe1-z)(IxBr1-x) solid solutions as tuneable materials for sustainable energy applications
David Rovira, Ivan Caño, Cibran Lopez et al. (+16 more)
Quasi-one-dimensional (Q-1D) van der Waals chalcohalides have emerged as promising materials for advanced energy applications, combining tunable optoelectronic properties and composed by earth-abundant and non-toxic elements. However, their widespread application remains hindered by challenges such as anisotropic
crystal growth, composition control and lack of knowledge on optoelectronic properties. A deeper understanding of the intrinsic limitations of these materials, as well as viable defect mitigation strategies like the engineering of solid solutions, is critical. This work presents a low-temperature synthesis route based on molecular ink deposition enabling direct crystallization of tunable Bi(SzSe1-z)(IxBr1-x) solid solutions without need for binary chalcogenide precursors. This approach yields phase-pure films with precise control over morphology, composition, and crystallographic orientation. XRD analysis and DFT calculations confirm the formation of homogeneous solid solutions, while optoelectronic measurements reveal the distinct roles of halogen and chalcogen anions in tuning bandgap energy and carrier type, with Se shifting downwards the conduction band. The versatility of this synthesis technique enables morphology control ranging from compact films to rod-shaped microcrystals, expanding the functional adaptability of these materials. These findings offer a foundational framework for defect engineering and the scalable integration of chalcohalides in next-generation energy technologies, including photovoltaics, photocatalysis, thermoelectrics, and chemical sensing.
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All authors David Rovira, Ivan Caño, Cibran Lopez, Alejandro Navarro-Güell, José Miguel Asensi, Lorenzo Calvo-Barrio, Laura Garcia-Carreras, Xavier Alcobe, Luis Cerqueira, Victoria Corregidor, Yudania Sanchez, Sonia Lanzalaco, Alex Jimenez-Arquijo, Outman El Khouja, Jonathan W. Turnley, Rakesh Agrawal, Claudio Cazorla, Joaquim Puigdollers, Edgardo Saucedo
Soft Condensed Matter
Phase Transitions of Oscillating Droplets on Horizontally Vibrating Substrates
King L. Ng, Luís H. Carnevale, Michał Klamka et al. (+3 more)
Droplet deformations caused by substrate vibrations are ubiquitous in nature and highly relevant for applications such as microreactors and single-
cell sorting. The vibrations can induce droplet oscillations, a fundamental process that requires an in-depth understanding. Here, we report on extensive many-body dissipative particle dynamics simulations carried out to study the oscillations of droplets of different
liquids on horizontally vibrating substrates, covering a wide range of vibration frequencies and amplitudes as well as substrate wettability. We categorize the phases observed for different parameter sets based on the capillary number and identify the transitions between the observed oscillation phases, which are characterized by means of suitable parameters, such as the angular momentum and vorticity of the droplet. The instability growth rate for oscillation phase II, which leads to highly asymmetric oscillations and eventual droplet breakup, is also determined. Finally, we characterize the state of the droplet for the various scenarios by means of the particle-particle and particle-substrate contacts. We find a steady-state scenario for phase I, metastable breathing modes for phase II, and an out-of-
equilibrium state for phase III. Thus, we anticipate that this study provides much needed insights into a fundamental phenomenon in nature with significant relevance for applications.
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All authors King L. Ng, Luís H. Carnevale, Michał Klamka, Piotr Deuar, Tomasz Bobinski, Panagiotis E. Theodorakis
Statistical Mechanics
Velocity modulus diffusion of self-propelled spherical and circular particles: A generalized Langevin approach
Pedro J. Colmenares
This research presents a framework for describing the average velocity magnitude of an accelerated, self-propelled Brownian particle diffusing in a thermal fluid and confined by a harmonic external potential. The system is immersed in a thermal bath of harmonic oscillators at a constant temperature, where the bath constituents also interact with the external field. The dynamics are investigated for both a sphere and a disk, partitioned into two distinct
stochastic processes. The first process describes the coarse-grained, time-dependent internal self-velocity generated by a set of independent Ornstein-Uhlenbeck processes, independent of the external field. This internal mechanism provides the initial velocity for the particle to diffuse within the fluid, which is modeled via a modified generalized Langevin equation as the second process. We find that the system exhibits spontaneous fluctuations in the diffusive velocity magnitude due to the internal mechanism; however, as expected, these momentary fluctuations decay at long times. Finally, the internal propulsion velocity magnitude in spherical coordinates is derived, accompanied by simulations of the different magnitudes for both the sphere and the disk, the latter following established equations in polar coordinates.
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Other Condensed Matter
Characterization of heat transfer in 3D CMOS structures using Sideband Scanning Thermal Wave Microscopy
Valentin Fonck, Mohammadali Razeghi, Jean Spièce et al. (+5 more)
Efficient thermal management is critical for cryogenic CMOS
circuits, where local heating can compromise device performance and
qubit coherence. Understanding heat flow at the nanoscale in these multilayer architectures requires localized, high-resolution thermal probing techniques capable of accessing buried structures. Here, we introduce a sideband thermal wave detection scheme for Scanning Thermal Microscopy, S-STWM, to probe deeply buried heater structures within CMOS dies. By extracting the phase of propagating thermal waves, this method provides spatially resolved insight into heat dissipation pathways through complex multilayer structures. Our approach enables quantitative evaluation of thermal management strategies, informs the design of cryo-CMOS
circuits, and establishes a foundation for in situ thermal characterization under cryogenic operating conditions.
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All authors Valentin Fonck, Mohammadali Razeghi, Jean Spièce, Phillip Dobson, Jonathan Weaver, George Ridgard, Grayson M. Noah, Pascal Gehring
Disordered Systems and Neural Networks
Ground State Excitations and Energy Fluctuations in Short-Range Spin Glasses
C.M. Newman and D.L. Stein
We study the stability of ground states in the Edwards-Anderson Ising
spin glass in dimensions two and higher against perturbations of a single coupling. After reviewing the concepts of critical droplets, flexibilities and metastates, we show that, in any dimension, a certain kind of critical droplet with space-filling (i.e., positive spatial density) boundary does not exist in ground states generated by coupling-independent boundary conditions. Using this we show that if incongruent ground states exist in any dimension, the variance of their energy difference restricted to finite volumes scales proportionally to the volume. This in turn is used to prove that a metastate generated by (e.g.) periodic boundary conditions is unique and supported on a single pair of
spin-reversed ground states in two dimensions. We further show that any excitation above an infinite-volume ground state with a positive-density interface must have the property that its energy difference with the ground state in a restricted volume diverges as the square root of the restricted volume.
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Materials Science
First-principles calculations of thermal transport at metal/silicon interfaces: evidence of interfacial electron-phonon coupling
Michaël De San Féliciano, Christophe Adessi, Julien El Hajj et al. (+4 more)
With the increasing miniaturization of electronic components and the need to optimize thermal management, it has become essential to understand heat transport at metal/
semiconductor interfaces. While it has been recognized decades ago that an electron
phonon channel may take place at metal-
semiconductor interfaces, its existence is still controversial. Here, we investigate thermal transport at metal-silicon interfaces using the combination of first principles calculations and nonequilibrium Green's function (NEGF). We explain how to correct NEGF formalism to account for the out of
equilibrium nature of the energy carriers in the vicinity of the interface. The relative corrections to the
equilibrium distribution are shown to arise from the spectral mean free paths of silicon and may reach 15 percents. Applying these corrections, we compare the predictions of NEGF to available experimental data for Au/Si, Pt/Si and Al/Si interfaces. Based on this comparison, we infer the value of the electron
phonon interfacial thermal conductance by employing the two temperature model. We find that interfacial thermal transport at Au/Si interfaces is mainly driven by
phonon phonon processes, and that electron
phonon processes play a negligible role in this case. By contrast, for Al/Si interfaces, we show that
phonon-
phonon scattering alone can not explain the experimental values reported so far, and we estimate that the electron-
phonon interfacial conductance accounts for one third of the total conductance. This work demonstrates the importance of the electron-
phonon conductance at metal-silicon interfaces and calls for systematic experimental investigation of thermal transport at these interfaces at low temperatures. It paves the way for an accurate model to predict the conductance associated to the interfacial electron
phonon channel.
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All authors Michaël De San Féliciano, Christophe Adessi, Julien El Hajj, Nicolas Horny, François Detcheverry, Manuel Cobian, Samy Merabia
Mesoscale and Nanoscale Physics
On-chip cavity electro-acoustics using lithium niobate phononic crystal resonators
Jun Ji, Joseph G. Thomas, Zichen Xi et al. (+7 more)
Mechanical systems are pivotal in
quantum technologies because of their long coherent time and versatile coupling to
qubit systems. So far, the coherent and dynamic control of gigahertz-frequency mechanical modes mostly relies on optomechanical coupling and piezoelectric coupling to superconducting
qubits. Here, we demonstrate on-chip cavity electro-acoustic dynamics using our microwave-frequency electrically-modulated phononic-
crystal (PnC) resonators on lithium niobate (LN). Leveraging the high dispersion of PnC, our phononic modes space unevenly in the frequency spectrum, emulating atomic energy levels. Atomic-like transitions between different phononic modes are achieved by applying electrical fields to modulate phononic modes via nonlinear piezoelectricity of LN. Among two modes, we demonstrate Autler-Townes splitting (ATS), alternating current (a.c.) Stark shift, and Rabi oscillation with a maximum cooperativity of 4.18. Extending to three modes, we achieve non-reciprocal frequency conversions with an isolation up to 20 dB. Nonreciprocity can be tuned by the time delay between the two modulating pulses. Our cavity electro-acoustic platform could find broad applications in sensing, microwave signal processing, phononic computing, and
quantum acoustics.
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All authors Jun Ji, Joseph G. Thomas, Zichen Xi, Liyang Jin, Dayrl P. Briggs, Ivan I. Kravchenko, Arya G. Pour, Liyan Zhu, Yizheng Zhu, Linbo Shao
Materials Science · Cross-listed from physics.optics
Unveiling Spin Transition at Single Particle Level in Levitating Spin Crossover Nanoparticles
Elena Pinilla-Cienfuegos, Lucas Mascaró-Burguera, Ramón Torres-Cavanillas et al. (+4 more)
The ability to control and understand the phase transitions of individual nanoscale building blocks is key to advancing the next generation of low-power reconfigurable nanophotonic devices. To address this critical challenge, molecular nanoparticles (NPs) exhibiting a
spin crossover (SCO) phenomenon are trapped by coupling a quadrupole Paul trap with a multi-spectral polarization-resolved scattering microscope. This contact-free platform simultaneously confines, optically excites, and monitors the
spin transition in Fe(II)-triazole NPs in a pressure-tunable environment, eliminating substrate artifacts. Thus, we show light-driven manipulation of the
spin transition in levitating NPs free from substrate-induced effects. Using the robust
spin bistability near room temperature of our SCO system, we quantify reversible opto-volumetric changes of up to 6%, revealing precise switching thresholds at the single-particle level. Independent pressure modulation produces a comparable size increase, confirming mechanical control over the same bistable transition. These results constitute full real-time control and readout of
spin states in levitating SCO NPs, charting a route toward their integration into ultralow-power optical switches, data-storage elements, and nanoscale sensors.
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All authors Elena Pinilla-Cienfuegos, Lucas Mascaró-Burguera, Ramón Torres-Cavanillas, J. Ignacio Echavarría, Alejandro Regueiro, Eugenio Coronado, Javier Hernandez-Rueda
Strongly Correlated Electrons
Photoinduced excitonic magnetism in a multiorbital Hubbard system
Lei Geng, Sujay Ray and Philipp Werner
Multiorbital Hubbard models with Hund coupling and
crystal-field splitting exhibit an instability toward
spin-triplet excitonic order in the parameter regime characterized by strong local
spin fluctuations. Upon chemical doping, two distinct types of excitonic ferromagnetism have been reported. Using steady-state nonequilibrium dynamical mean-field theory, we demonstrate that photo-doped half-filled systems can host nonthermal counterparts of these excitonic phases and exhibit a rich phase diagram in the space of photo-doping and
crystal field splitting. Photo-doping a
spin-triplet excitonic
insulator provides a route towards nonequilibrium control of
magnetic order.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Inverse-Designed Grating Couplers with Tunable Wavelength via Scaling and Biasing
Lorenz J. J. Sauerzopf, Fabian Becker and Kai Müller
Photonic integrated
circuits are heavily researched devices for telecommunication, biosensing, and
quantum technologies. Wafer-scale fabrication and testing are crucial for reducing costs and enabling large-scale deployment. Grating couplers allow non-invasive measurements before packaging, but classical designs rely on long tapers and narrow bandwidths. In this work, we present compact, inverse-designed grating couplers with broadband transmission. We optimized and fabricated arrays of devices and characterized them with a 4f-scanning setup. The nominal design reached simulated efficiencies of 52 %, while measurements confirmed robust performance with up to 32 % efficiency at the target 1540 nm wavelength and 46 % at shifted wavelengths. Without scaling and contour biasing, the measured efficiency at the target wavelength drops to only 4.4 %. Thus, a key finding is that systematic scaling and edge biasing recover up to an eightfold improvement in efficiency. These inverse-designed grating couplers can be efficiently corrected post-design, enabling reliable performance despite fabrication deviations. This approach allows simple layout adjustments to compensate for process-induced variations, supporting wafer-scale testing, cryogenic photonic applications, and rapid design wavelength tuning.
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Quantum Gases · Cross-listed from physics.atom-ph
Long-lived giant circular Rydberg atoms at room temperature
Einius Pultinevicius, Aaron Götzelmann, Fabian Thielemann et al. (+2 more)
Stability achieved by large angular momentum is ubiquitous in nature, with examples ranging from classical mechanics, over optics and chemistry, to
nuclear physics. In atoms, angular momentum can protect excited electronic orbitals from decay due to selection rules. This manifests spectacularly in highly excited Rydberg states. Low angular momentum Rydberg states are at the heart of recent breakthroughs in
quantum computing, simulation and sensing with neutral atoms. For these applications the lifetime of the Rydberg levels sets fundamental limits for gate fidelities, coherence times, or spectroscopic precision. The quest for longer Rydberg state lifetimes has motivated the generation, coherent control and trapping of circular Rydberg atoms, which are characterized by the maximally allowed electron orbital momentum and were key to seminal experiments with single atoms and
photons. Here, we report the observation of individually trapped circular Rydberg atoms with lifetimes of more than 10 milliseconds, two orders of magnitude longer-lived than the established low angular momentum orbitals. This is achieved via Purcell suppression of blackbody modes at room temperature. We coherently control individual circular Rydberg levels at so far elusive principal
quantum numbers of up to $n=103$, and observe tweezer trapping of the Rydberg atoms on the hundred millisecond scale. Our results pave the way for
quantum information processing and sensing utilizing the combination of extreme lifetimes and
giant Rydberg blockade.
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All authors Einius Pultinevicius, Aaron Götzelmann, Fabian Thielemann, Christian Hölzl, Florian Meinert
Statistical Mechanics
Snap, Crackle, and Pop: This is why the potential of mean force clashes with the fluctuation dissipation relation
Fabian Koch, Tabita Wasmer and Tanja Schilling
We analyze the non-linear generalized Langevin equation which contains a thermodynamic force. We show that even for systems in thermal
equilibrium the presence of the thermodynamic force implies that the auto-correlation function of the fluctuating force becomes non-stationary. We further illustrate that a standard coarse-graining procedure that neglects this fact predicts waiting-time distributions incompatible with the original, microscopic process. We conclude that one needs to proceed with care when adding thermodynamic driving forces to the Langevin equation.
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Materials Science
Size-dependent transformation patterns in NiTi tubes under tension and bending: Stereo digital image correlation experiments and modeling
Aslan Ahadi, Elham Sarvari, Jan Frenzel et al. (+3 more)
The dependence of transformation pattern in superelastic NiTi tubes on tube outer diameter D and wall-thickness t is investigated through quasi-static uniaxial tension and large-rotation bending experiments. The
evolution of outer-surface strain fields is synchronized with global stress-strain and moment-
curvature responses using a multi-magnification, high-resolution stereo digital image correlation system at 0.5-2x magnifications. The transformation patterns exhibit systematic size-dependent behaviors. Under tension and for a specific D, as the diameter-to-thickness ratio D/t decreases, a decreasing number of fat/diffuse helical bands emerge, in contrast to sharp/slim bands in thin tubes. Consequently, the austenite-martensite front morphology transitions from finely-fingered to coarsely-fingered with decreasing D/t. Below a characteristic D/t, front morphology no longer exhibits patterning and phase transformation proceeds via propagation of a finger-less front. Moreover, the transformation pattern exhibits an interrelation between D and D/t, where a front possessing diffuse fingers is observed in a thin but small tube. Under bending, both the global moment-
curvature response and transformation pattern exhibit D- and D/t-dependence. While wedge-like martensite domains consistently form across all tube sizes, their growth is noticeably limited in smaller and thicker tubes due to geometrical constraints. A gradient-enhanced model of superelasticity is employed to analyze the distinct transformation patterns observed in tubes of various dimensions. The size-dependent behavior is explained based on the competition between bulk and interfacial energies, and the energetic cost of accommodating martensite fingers. By leveraging an axisymmetric tube configuration as a reference energy state, the extra energy associated with the formation of fingers is quantified.
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All authors Aslan Ahadi, Elham Sarvari, Jan Frenzel, Gunther Eggeler, Stanisław Stupkiewicz, Mohsen Rezaee-Hajidehi
Strongly Correlated Electrons
First-Order Spin-Reorientation Transition and Incomplete Softening of the Antiferromagnetic Resonance Mode in Multiferroic GdFe$_3$(BO$_3$)$_4$
I. N. Khoroshiy, S. A. Skorobogatov, S. E. Nikitin et al. (+3 more)
The multiferroic ferroborate GdFe$_3$(BO$_3$)$_4$ with huntite-type structure exhibits
magnetic ordering below T$_N$ = 38 K and contains two
magnetic subsystems associated with Gd and Fe ions. Competing anisotropies of these subsystems drive a
spin reorientation transition at T$_{SR}$ = 10.7 K, switching the ground state from easy-axis to easy-plane. Using
antiferromagnetic resonance, we investigate the
spin dynamics across this transition. The observed incomplete softening of a
magnon mode during both field- and temperature-induced
spin-reorientation transitions indicates the first-order nature of the phase transition, which is accompanied by a discontinuous jump in the effective anisotropy field. We reproduce this behavior using a simple model that attributes the jump in the anisotropy field to the presence of an effective fourth-order anisotropy constant, responsible for the discontinuous character of the transition. Remarkably, for in-plane
magnetic fields, we identify a new AFMR mode that persists from 12 K up to T$_N$. This mode likely corresponds to the dynamics of a long period incommensurate state, previously detected by resonant elastic X-ray scattering.
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All authors I. N. Khoroshiy, S. A. Skorobogatov, S. E. Nikitin, I. A. Gudim, V. R. Titova, A. I. Pankrats
Materials Science
Density functional investigations on 2D-Be2C as an anode for alkali Metal-ion batteries
Hetvi Jadav, Sadhana Matth and Himanshu Pandey
Metal-ion batteries are in huge demand to cope with the increasing need for renewable energy, especially in automobiles. In this work, we apply first-principle calculations to examine two-dimensional beryllium carbide (2D-Be2C) as a possible anode material for metal-ion (Na and K) batteries. 2D-Be2C is a
semiconductor and becomes metallic by adsorbing metal ions. Negative adsorption energy indicates stable adsorption on the monolayer of Be2C. Alkali metal
diffusion barrier and optimum path for minimum energy are studied within the framework of the climbing image nudged elastic band method. Here, six intermediate images are considered between the initial and final states. The lowest
diffusion barriers for a single adsorbed Na and K atom are 0.016 and 0.026 eV, respectively. A maximum open
circuit voltage of around 1 V is computed for K ions, whereas 0.5 V is for Na ions. Also, the maximum storage capacity of the Be2C monolayer is estimated at 1785 Ah/kg.
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Materials Science
Hexagonal BeX (X: S, Te) monolayer as potential electrode material for alkali metal-ion batteries: A DFT perspective
Hetvi Jadav, Sadhana Matth and Himanshu Pandey
Metal-ion batteries (MIBs) are essential for transitioning to a cleaner and more sustainable energy future. By employing the density functional formalism, we have investigated the hexagonal (h) monolayer of BeS and BeTe as electrode materials for alkali (Li and Na) MIBs. The structural and thermodynamic stability, adsorption of Li/Na atoms, density of states,
diffusion, and migration of atoms, as well as capacity, are systematically investigated. The structures of h-BeS and h-BeTe remain stable upon the adsorption of adatoms, resulting in improved electronic conductivity of these monolayers. The climbing image-nudged elastic band calculations estimate a low
diffusion barrier of 0.16 eV (0.01 eV) for Li (Na) in h-BeS and 0.20 eV (0.16 eV) for Li (Na) in h-BeTe. Additionally, a maximum storage capacity of 580 mAh g-1 for Li and 1305 mAh g-1 for Na in h-BeS, as well as 174 mAh g-1 for h-BeTe, is estimated for both metal ions.
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Quantum Gases
Fate and origin of the quantum Otto heat engine based on the dissipative Dicke-Hubbard model
He-Guang Xu and Shujie Cheng
The Dicke-Hubbard model, describing an ensemble of interacting atoms in a cavity, provides a rich platform for exploring collective
quantum phenomena. However, its potential for
quantum thermodynamic applications remains largely uncharted. Here, we study a
quantum Otto heat engine whose working substance is a system governed by the Dicke-Hubbard
Hamiltonian. Through the research on steady-state superradiance phase transitions, it is demonstrated that the steady-state synergistic mechanism under high and low temperature environments is the reason for the emergence of high-performance heat engines. By analyzing the influences of atom-light coupling strength, inter-cavity hopping strength and atom number on the working modes of
quantum Otto cycle, it is clarified that the effective working regions of each working mode. This work has established a close connection between superradiance phase transition and the
quantum thermodynamic applications. It not only deepens our understanding of the energy conversion mechanism in non-
equilibrium quantum thermodynamics but also lays a theoretical foundation for the future experimental design of high-performance
quantum Otto heat engines.
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Materials Science
High-performance thermochromic multilayer coatings with W-doped VO2 nanoparticles dispersed in SiO2 matrix prepared on glass at a low temperature
Jaroslav Vlcek, Michal Kaufman, Elnaz M. Nia et al. (+5 more)
We report a high-performance thermochromic VO2-based coating prepared by using a three-step process, consisting of magnetron sputter depositions of SiO2 films and V-W films and their postannealing, on standard glass at a low substrate temperature of 350 {\deg}C without opening the
vacuum chamber to atmosphere. It is formed by four layers of W-doped VO2 nanoparticles dispersed in SiO2
matrix. The coating exhibits a transition temperature of 33 {\deg}C with an integral luminous transmittance of 65.4% (low-temperature state) and 60.1% (high-temperature state), and a modulation of the
solar energy transmittance of 15.3%. Such a combination of properties, together with the low temperature during preparation, fulfill the requirements for large-scale implementation on building glass and have not been reported yet.
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All authors Jaroslav Vlcek, Michal Kaufman, Elnaz M. Nia, Jiri Houska, Jiechao Jiang, Radomir Cerstvy, Stanislav Haviar, Efstathios I. Meletis
Materials Science
Lattice dynamics in chiral tellurium by linear and circularly polarized Raman spectroscopy: crystal orientation and handedness
Davide Spirito, Sergio Marras and Beatriz Martín-García
Trigonal tellurium (Te) has attracted researchers'
attention due to its transport and optical properties, which include electrical magneto-
chiral anisotropy,
spin polarization and bulk photovoltaic effect. It is the anisotropic and
chiral crystal structure of Te that drive these properties, so the determination of its crystallographic orientation and handedness is key to their study. Here we explore the structural dynamics of Te bulk
crystals by angle-dependent linearly polarized Raman spectroscopy and
symmetry rules in three different crystallographic orientations. The angle-dependent intensity of the modes allows us to determine the arrangement of the helical chains and distinguish between crystallographic planes parallel and perpendicular to the chain axis. Furthermore, under different configurations of circularly polarized Raman measurements and
crystal orientations, we observe the shift of two
phonon modes only in the (0 0 1) plane. The shift is positive or negative depending on the handedness of the
crystals, which we determine univocally by chemical etching. Our analysis of three different
crystal faces of Te highlights the importance of selecting the proper orientation and crystallographic plane when investigating the transport and optical properties of this material. These results offer insight into the
crystal structure and
symmetry in other anisotropic and
chiral materials, and open new paths to select a suitable
crystal orientation when fabricating devices.
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Soft Condensed Matter
Salt crystallization and deliquescence triggered by humidity cycles in nanopores
Hugo Bellezza, Marine Poizat and Olivier Vincent
We study the response of materials with nanoscale pores containing sodium chloride solutions, to cycles of relative humidity (RH). Compared to pure fluids, we show that these sorption isotherms display much wider hysteresis, with a shape determined by salt crystallization and deliquescence rather than capillary condensation and Kelvin evaporation. Both deliquescence and crystallization are significantly shifted compared to the bulk and occur at unusually low RH. We systematically analyze the effect of pore size and salt amount, and rationalize our findings using confined thermodynamics, osmotic effects and classical nucleation theory.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Advanced micropillar cavities: room-temperature operation of microlasers
Andrey Babichev, Alexey Blokhin, Yuriy Zadiranov et al. (+11 more)
High-quality micropillar cavities were grown using molecular-beam epitaxy. Stable continuous-wave lasing at room-temperature was demonstrated for microlasers with
semiconductor and hybrid output mirrors. At 300 K, single-mode lasing was demonstrated for micropillars with a diameter of 5 $\mu$m at a wavelength of 960 nm, with a minimum lasing threshold of 1.2 mW and a bare quality-factor exceeding 8000.
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All authors Andrey Babichev, Alexey Blokhin, Yuriy Zadiranov, Yulia Salii, Marina Kulagina, Mikhail Bobrov, Alexey Vasiliev, Sergey Blokhin, Nikolay Maleev, Ivan Makhov, Natalia Kryzhanovskaya, Leonid Karachinsky, Innokenty Novikov, Anton Egorov
Materials Science
Influence of Hydrogen-Incorporation on the Bulk Electronic Structure and Chemical Bonding in Palladium
L. J. Bannenberg, F. García-Martínez, P. Lömker et al. (+6 more)
Palladium hydride is a model system for studying metal-hydrogen interactions. Yet, its bulk electronic structure has proven difficult to directly probe, with most studies to date limited to surface-sensitive photoelectron spectroscopy approaches. This work reports the first in-situ ambient-pressure hard X-ray photoelectron spectroscopy (AP-HAXPES) study of hydrogen incorporation in Pd thin films, providing direct access to bulk chemical and electronic information at elevated hydrogen pressures. Structural characterisation by in-situ X-ray diffraction and
neutron reflectometry under comparable conditions establishes a direct correlation between hydrogen loading,
lattice expansion, and electronic modifications. Comparison with density functional theory (DFT) reveals how hydrogen stoichiometry and site occupancy govern the density of occupied states near the
Fermi level. These results resolve long-standing questions regarding PdH and establish AP-HAXPES as a powerful tool for probing the bulk electronic structure of metal hydrides under realistic conditions.
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All authors L. J. Bannenberg, F. García-Martínez, P. Lömker, R. Y. Engel, C. Schlueter, H. Schreuders, A. Navarathna, L. E. Ratcliff, A. Regoutz
Mesoscale and Nanoscale Physics
Single femtosecond laser pulse-driven ferromagnetic switching
Chen Xiao, Boyu Zhang, Xiangyu Zheng et al. (+18 more)
Light pulses offer a faster, more energy-efficient, and direct route to
magnetic bit writing, pointing toward a hybrid
memory and computing paradigm based on
photon transmission and
spin retention. Yet progress remains hindered, as deterministic, single-pulse optical toggle switching has so far been achieved only with ferrimagnetic materials, which require too specific a rare-earth composition and temperature conditions for technological use. In mainstream ferromagnet–central to spintronic
memory and storage–such bistable switching is considered fundamentally difficult, as
laser-induced heating does not inherently break time-reversal
symmetry. Here, we report coherent magnetization switching in ferromagnets, driven by thermal anisotropy torque with single
laser pulses. The toggle switching behavior is robust over a broad range of pulse durations, from femtoseconds to picoseconds, a prerequisite for practical applications. Furthermore, the phenomenon exhibits reproducibility in CoFeB/MgO-based
magnetic tunnel junctions with a high magnetoresistance exceeding 110%, as well as the scalability down to nanoscales with remarkable energy efficiency (17 fJ per 100-nm-sized bit). These results mark a notable step toward integrating opto-spintronics into next-generation
memory and storage technologies.
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All authors Chen Xiao, Boyu Zhang, Xiangyu Zheng, Yuxuan Yao, Jiaqi Wei, Dinghao Ma, Yuting Gong, Rui Xu, Xueying Zhang, Yu He, Wenlong Cai, Yan Huang, Daoqian Zhu, Shiyang Lu, Kaihua Cao, Hongxi Liu, Pierre Vallobra, Xianyang Lu, Youguang Zhang, Bert Koopmans, Weisheng Zhao
Soft Condensed Matter
Domain Growth and Aging in a Phase Separating Binary Fluid Confined Inside a Nanopore
Saikat Basu, Suman Majumder, Raja Paul et al. (+1 more)
Hydrodynamics is known to have strong effects on the kinetics of phase separation. There exist open questions on how such effects manifest in systems under confinement. Here, we have undertaken extensive studies of the kinetics of phase separation in a two-component fluid that is confined inside pores of cylindrical shape. Using a hydrodynamics-preserving thermostat, we carry out molecular dynamics simulations to obtain results for domain growth and aging for varying temperature and pore-width. We find that all systems freeze into a morphology where stripes of regions rich in one or the other component of the mixture coexist in a locked situation. Our analysis suggests that, irrespective of the temperature the growth of the average domain size, $\ell(t)$, prior to the freezing into stripped patterns, follows the power law $\ell(t)\sim t^{2/3}$, suggesting an inertial hydrodynamic growth, which typically is applicable for bulk fluids only in the asymptotic limit. Similarly, the aging dynamics, probed by the two-time order-parameter autocorrelation function, also exhibits a temperature-independent power-law scaling with an exponent $\lambda \simeq 2.55$, much smaller than what is observed for a bulk fluid.
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All authors Saikat Basu, Suman Majumder, Raja Paul, Subir K. Das
Statistical Mechanics
Information geometry of perturbed gradient flow systems on hypergraphs: A perspective towards nonequilibrium physics
Dimitri Loutchko, Keisuke Sugie and Tetsuya J Kobayashi
This article serves to concisely review the link between gradient flow systems on hypergraphs and information geometry which has been established within the last five years. Gradient flow systems describe a wealth of physical phenomena and provide powerful analytical technquies which are based on the variational energy-dissipation principle. Modern nonequilbrium physics has complemented this classical principle with thermodynamic uncertaintly relations, speed limits,
entropy production rate decompositions, and many more. In this article, we formulate these modern principles within the framework of perturbed gradient flow systems on hypergraphs. In particular, we discuss the geometry induced by the Bregman divergence, the physical implications of dual foliations, as well as the corresponding infinitesimal Riemannian geometry for gradient flow systems. Through the geometrical perspective, we are naturally led to new concepts such as
moduli spaces for perturbed gradient flow systems and thermodynamical area which is crucial for understanding speed limits. We hope to encourage the readers working in either of the two fields to further expand on and foster the interaction between the two fields.
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Materials Science · Cross-listed from physics.bio-ph
Spatial organization of biomass controls intrinsic permeability of porous systems
Wenqiao Jiao, David Scheidweiler, Nolwenn Delouche et al. (+2 more)
Biofilms in porous media critically influence hydraulic properties in environmental and engineered systems. However, a mechanistic understanding of how microbial life controls permeability remains elusive. By combining microfluidics, controlled pressure gradient and time-lapse microscopy, we quantify how motile and non-motile bacteria colonize a porous landscape and alter its resistance to flow. We find that while both strains achieve nearly identical total biomass, they cause drastically different permeability reductions - 78% for motile
cells versus 94% for non-motile
cells. This divergence stems from motility, which limits biomass spatial accumulation, whereas non-motile
cells clog the entire system. We develop a mechanistic model that accurately predicts permeability dynamics from the pore-scale biomass distribution. We conclude that the spatial organization of biomass, not its total amount, is the primary factor controlling permeability.
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All authors Wenqiao Jiao, David Scheidweiler, Nolwenn Delouche, Alberto Guadagnini, Pietro de Anna
Strongly Correlated Electrons
Ground states of a family of frustrated spin models for quasicrystals and their approximants
Anuradha Jagannathan
Many new families of quasicrystal-forming
magnetic alloys have been synthesized and studied in recent years. For small changes of composition, the
alloys can go from quasiperiodic to periodic (approximant
crystals) while conserving most of the local atomic environments. Experiments show that many of the periodic approximants order at low temperatures, with clear signatures of
ferromagnetic or
antiferromagnetic transitions, and also in some cases undergo non-
equilibrium spin glass transitions. In contrast, the quasicrystals are mostly found to be
spin glasses. Systematically studying these
alloys could help elucidate the role played by quasiperiodicity in (de)stabilizing long range
magnetic order. In this work, we study cluster
spin models with the aim of understanding the mechanisms behind various types of long range
magnetic ordering in approximants and quasicrystals. These models embody key features of real systems, and to some extent are analytically tractable, both for periodic and quasiperiodic cases. For the quasicrystal, we describe two novel
magnetic phases with quasiperiodic ordering. Our results should serve to motivate further studies with detailed numerical explorations of this family of models.
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Materials Science
The plastic flow of polycrystalline solids
Miguel Lagos
A polycrystalline solid is modelled as an ensemble of random irregular polyhedra filling the entire space occupied by the solid body, leaving no voids or flaws between them. Adjacent grains can slide with a relative velocity proportional to the local shear stress resolved in the plane common to the two sliding grains, provided it exceeds a threshold. The local forces associated to the continuous grain shape accommodation for preserving matter continuity are assumed much weaker. The model can be solved analytically and for overcritical conditions gives two regimes of deformation, plastic and superplastic. The plastic regime, from yield to fracture, is dealt with. Applications to nickel superalloys and stainless steels give impressive agreement with experiment. Most work of the last century relies on postulating pre–existent cracks and voids to explain plastic deformation and fracture. The present model gives much better results.
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Materials Science
First-principles design of excitonic insulators: A review
H. W. Qu, H. T. Liu and Y. C. Li
The excitonic
insulator (EI) is a more than 60-year-old theoretical proposal that yet remains elusive. It is a purely
quantum phenomenon involving the spontaneous generation of
excitons in
quantum mechanics and the spontaneous condensation of
excitons in
quantum statistics. At this point, the
excitons represent the ground state rather than the conventional excited state. Thus, the scarcity of candidate materials is a key factor contributing to the lack of recognized EI to date. In this review, we begin with the birth of EI, presenting the current state of the field and the main challenges it faces. We then focus on recent advances in the discovery and design of EIs based on the first-principles Bethe-Salpeter scheme, in particular the dark-
exciton rule guided screening of materials. It not only opens up new avenues for realizing excitonic instability in direct-gap and wide-gap
semiconductors, but also leads to the discovery of novel
quantum states of matter such as half-EIs and
spin-triplet EIs. Finally, we will look ahead to possible research pathways leading to the first recognized EI, both computationally and theoretically.
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Mesoscale and Nanoscale Physics
Theoretical Investigation of Anomalous Hall and Nernst Responses in Potassium Tri Vanadium Pentantimonide
Partha Goswami
We present a theoretical study of the anomalous Nernst and
Hall conductance in the Kagome metal potassium tri vanadium pentantimonide, based on a system
Hamiltonian incorporating nearest neighbour and complex next nearest neighbour hopping, Rashba
spin orbit coupling, an exchange field induced by
magnetic proximity, and a charge density wave potential. Our analysis reveals that the Nernst conductivity exhibits a non monotonic temperature dependence. It increases with temperature, reaches a pronounced peak, and subsequently declines at higher temperatures due to thermal broadening, which diminishes the influence of Berry
curvature. Notably, small shifts in the chemical potential can lead to dramatic changes in the Nernst signal enhancing its magnitude or even reversing its sign highlighting the system sensitivity to carrier density. We further explore the anomalous
Hall behaviour within this framework. The band structure hosts multiple bands with nonzero Berry
curvature, and preliminary Chern number calculations suggest weak topological features, namely, while not fully quantized, the system exhibits significant Berry
curvature accumulation. Upon introducing momentum space winding, implemented via a momentum dependent phase in the complex hopping terms to mimic orbital
magnetic flux, we observe that two bands acquire opposite Chern numbers. The remaining bands remain topologically trivial.
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