Materials Science
Effect of crystallographic texture on dealloying kinetics and composition of nanoporous gold surface
Ezgi Hatipoğlu, Ayman A. El-Zoka, Yujun Zhao et al. (+4 more)
Nanoporous metals allow for tailoring composition and surface-to-volume ratio, both aspects critical for applications in catalysis. Here, Ag70Au30 (2 at. %) films with a face-centered cubic structure were deposited at 400{\deg}C, either {111}-textured or randomly oriented. Upon chemical dealloying, atom probe
tomography of the nanoporous structure reveals that the textured film retains a up to 2.7 times higher Ag concentration within the ligaments compared to the randomly oriented film that exhibits ligament coarsening, indicating faster dealloying kinetics. Our study highlights the potential of microstructure engineering in tailoring the properties of nanoporous metals for possible future catalytic and electrochemical applications.
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All authors Ezgi Hatipoğlu, Ayman A. El-Zoka, Yujun Zhao, Stanislav Mráz, Jochen M. Schneider, Baptiste Gault, Aparna Saksena
Statistical Mechanics
Analytic expressions for estimation of the critical properties of inhomogeneous Ising models
Vladislav Egorov and Stepan Osipov
In many applications of
spin models, the fast estimation of their critical temperatures and other physical properties is of great importance. In this work, we present the analytical expressions estimating the critical properties of inhomogeneous Ising models with
ferromagnetic interactions. The expressions were obtained within the framework of the m-vicinity method. The accuracy of the critical temperature estimations was evaluated through comparison with Monte Carlo simulations. Special
attention was given to the case when the model consists of two interacting interpenetrating homogeneous sublattices, and relationships for the compositional dependence of the critical temperature were derived.
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Materials Science
Autonomous interpretation of atomistic scattering data
Andy S. Anker, John L. A. Gardner, Louise A. M. Rosset et al. (+2 more)
Materials with bespoke properties have long been identified by computational searches, and their experimental realisation is now coming within reach through autonomous laboratories. Scattering experiments are central to verifying the atomic structures of autonomously synthesised materials. Yet, interpreting these measurements typically requires user expertise and manual processing, or machine learning (ML) models trained on predefined
datasets, limiting fully autonomous materials discovery. Here, we introduce a differentiable optimisation framework that treats scattering calculations, energetics, and chemical constraints as a unified refinement problem. Capability demonstrations across molecules,
crystal structures, nanoparticles, and amorphous matter show that this data-driven approach resolves structural degeneracies with multi-modal inputs - suggesting its usefulness for informing, and ultimately guiding, the operation of autonomous laboratories.
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All authors Andy S. Anker, John L. A. Gardner, Louise A. M. Rosset, Andrew L. Goodwin, Volker L. Deringer
Materials Science
Retardance of lab grown diamond substrates as a function of thickness: momentum-drift random walk model
Thanh Tran, Phuong Vo, Thomas Sheppard et al. (+2 more)
This work studies the correlation between mean retardance and thickness of diamond substrates grown homoepitaxially via microwave
plasma-enhanced chemical vapor deposition (MPCVD). We measure the retardance of a diamond substrate in two orientations: perpendicular and parallel to the growth direction. Our experimental results demonstrate that the correlation between mean retardance and thickness differs for these orientations. When measured perpendicular to the growth direction, the mean retardance is approximately proportional to the square root of the substrate thickness. In contrast, when measured parallel to the growth direction, we observe a generally higher mean retardance and an approximately linear correlation with thickness. This anisotropy arises not from differences in stress magnitude but from differences in the interlayer correlation of the principal stress axes, as evidenced by correlation coefficients between the azimuth angles of consecutive layers in the diamond
crystal. To simulate the integrated retardance of diamond wafers, we propose a two-dimensional random walk model with momentum drift, which captures the diamond
crystal tendency to preserve the azimuth angle across the samples. By optimizing the momentum factor, we show that the model can closely match experimental data. The momentum factor is found higher along the growth direction, which is consistent with the calculated correlation coefficients. Furthermore, both the model and experiments indicate that retardance-to-thickness ratios of thin samples converge toward similar base retardances in both orientations. These findings establish a quantitative framework for interpreting birefringence in diamond substrates, with implications for material selection and development in thermal management,
quantum sensing, high-power electronics, and optical applications.
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All authors Thanh Tran, Phuong Vo, Thomas Sheppard, Timothy Grotjohn, Paul Quayle
Materials Science
High- and medium-entropy nitride coatings from the Cr-Hf-Mo-Ta-W-N system: properties and high-temperature stability
Pavel Souček, Stanislava Debnárová, Šárka Zuzjaková et al. (+9 more)
High- and medium-
entropy nitride coatings from the Cr-Hf-Mo-Ta-W-N system were studied using ab initio calculations and experiments to clarify the role of
entropy and individual elements in phase stability, microstructure, and high-temperature behaviour. Formation energy calculations indicated that nitrogen vacancies stabilise the cubic (fcc) phase, with hafnium and tantalum acting as strong stabilisers, while tungsten destabilises the
lattice. Coatings were deposited by reactive magnetron sputtering at approx. 50C (AT) and approx. 580C (HT). All exhibited columnar fcc structures; high-temperature deposition produced denser coatings, lower nitrogen content, and larger crystallites, resulting in higher hardness and elastic modulus. Thermal stability was tested up to 1200C on Si and oxidation at 1400C on sapphire. AT coatings failed early, while most HT coatings endured. Nitrogen loss less than 10 at.% at 1000C was critical for survival. TEM revealed tungsten segregation and HfO2 formation, while fcc nitride remained dominant. Ta enrichment proved essential for superior thermal and oxidation stability.
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All authors Pavel Souček, Stanislava Debnárová, Šárka Zuzjaková, Shuyao Lin, Matej Fekete, Zsolt Czigány, Katalin Balázsi, Lukáš Vrána, Tatiana Pitoňáková, Ondřej Jašek, Petr Zeman, Nikola Koutná
Quantum Gases
From Lasers to Photon Bose–Einstein Condensates: A Unified Description via an Open-Dissipative Bose–Einstein Distribution
Joshua Krauß, Enrico Stein and Axel Pelster
Photon condensation was first experimentally realized in 2010 within a dye-filled microcavity at room temperature. Since then, interest in the field has increased significantly, as a
photon Bose-Einstein condensate (BEC) represents a prototypical driven-dissipative system. Here, we investigate how its inherent open nature influences the condensation process both quantitatively and qualitatively. To this end, we consider a mean-field model, which can be derived microscopically from a Lindblad master equation. The underlying rate equations depend on various external parameters such as emission and absorption rates of the dye molecules as well as the cavity
photon loss rate. In steady state, we obtain an open-dissipative Bose-Einstein distribution for the mode occupations. The chemical potential of this distribution depends on the occupations of the dye molecules in both their ground and excited state and must therefore be determined self-consistently. We find that the resulting
photon distribution is strongly influenced by the driven-dissipative parameters. Based on this result, we identify the main differences between a photonic BEC, an atomic BEC, and a
laser.
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Superconductivity
Superconducting Nanowire Single Photon Detectors based on NbRe nitride ultrafilms
F. Avitabile, F. Colangelo, M. Yu. Mikhailov et al. (+5 more)
The influence of the reactive DC sputtering parameters on the superconducting properties of NbReN ultrathin films was investigated. A detailed study of the current-voltage characteristics of the
plasma was performed to optimize the superconducting critical temperature, Tc. The thickness dependence of Tc for the films deposited under different conditions was analyzed down to the ultrathin limit. Optimized films were used to fabricate superconducting nanowire single
photon detectors which, at T=3.5 K, show saturated internal detection efficiency (IDE) up to a wavelength of 1301 nm and 95% IDE at 1548 nm with recovery times and timing jitter of about 8 ns and 28 ps, respectively.
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All authors F. Avitabile, F. Colangelo, M. Yu. Mikhailov, Z. Makhdoumi Kakhaki, A. Kumar, I. Esmaeil Zadeh, C. Attanasio, C. Cirillo
Strongly Correlated Electrons
Hidden phonon-assisted charge density wave transition in BaFe2Al9 revealed by ultrafast optical spectroscopy
Lei Wang, Mingwei Ma, Jiangxu Li et al. (+10 more)
The interplay between electronic and
lattice degrees of freedom is fundamental to charge density wave (CDW) formation, yet the microscopic origin often remains elusive. Here, we investigate the transient optical response of the intermetallic compound BaFe2Al9 using polarization-resolved ultrafast optical spectroscopy. We identify a discontinuous sign reversal in the transient reflectivity at Tc ~ 110 K, providing unambiguous evidence for the first-order transition. The anisotropic quasiparticle relaxation establishes the three-dimensional nature of the ordered state. Below Tc, a single coherent 1.6 THz oscillation appears abruptly and remains confined to the CDW phase. This mode exhibits weak temperature dependence with negligible softening and is absent in Raman spectra. First-principles calculations imply that it is a precursor
phonon at the CDW wave vector with strong electron-
phonon coupling. Our results indicate that the CDW in BaFe2Al9 arises from intertwined electronic and
lattice instabilities, assisted by a displacive mechanism mediated by a hidden strongly coupled
phonon, distinct from conventional amplitude-mode softening scenarios.
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All authors Lei Wang, Mingwei Ma, Jiangxu Li, Liucheng Chen, Bingru Lu, Xiang Li, Feng Jin, Elbert E. M. Chia, Jianlin Luo, Rongyan Chen, Peitao Liu, Fang Hong, Xinbo Wang
Quantum Gases · Cross-listed from quant-ph
Hybrid quantum-classical analog simulation of two-dimensional Fermi-Hubbard models with neutral atoms
Sergi Julià-Farré, Antoine Michel, Christophe Domain et al. (+11 more)
We experimentally study the two-dimensional
Fermi-Hubbard model using a Rydberg-based
quantum processing unit in the analog mode. Our approach avoids encoding directly the original
fermions into
qubits and instead relies on reformulating the original model onto a system of
fermions coupled to
spins and then decoupling them in a self-consistent manner. We then introduce the auxiliary
spin solver: this hybrid
quantum-classical
algorithm handles a free-
fermion problem, which can be solved efficiently with a few classical resources, and an interacting
spin problem, which can be naturally encoded in the analog
quantum computer. This
algorithm can be used to study both the
equilibrium Mott transition as well as non-
equilibrium properties of the original
Fermi-Hubbard model, highlighting the potential of
quantum-classical hybrid approaches to study strongly correlated matter.
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All authors Sergi Julià-Farré, Antoine Michel, Christophe Domain, Joseph Mikael, Jacques-Charles Lafoucriere, Joseph Vovrosh, Ahmed Chahlaoui, Dorian Claveau, Guillaume Villaret, Julius de Hond, Loïc Henriet, Antoine Browaeys, Thomas Ayral, Alexandre Dauphin
Materials Science
Confinement-Controlled Morphology and Stability of One-Dimensional CrI3 Nanotubes
Ihsan Caha, Aqrab ul Ahmad and Francis Leonard Deepak
Integrating monolayers derived from 2D van der Waals (vdW)
magnetic materials into next-generation technological applications remains a significant challenge due to their structural and
magnetic instability issues. Template-assisted encapsulation is a potential route for the growth of stable 2D monolayers aimed at designing novel 1D
heterostructures, opening new avenues for studying low-dimensional
quantum effects and
spin-related phenomena. In this study, we explored the diameter-dependent encapsulation of 2D CrI3
crystals using multi-walled carbon nanotubes as nanoscale host templates. Advanced microscopic analysis revealed distinct structural transitions, ranging from internal nanorod encapsulation to external shell formation, directly influenced by the host nanotube diameter. Furthermore, statistical analysis of structural morphologies indicates that CrI3 nanorods preferentially form within MWCNTs with inner diameters up to 5 nm, while single-walled CrI3 nanotubes are stabilized in CNTs with diameters up to 8 nm. For host CNTs exceeding 10 nm in diameter, CrI3 predominantly forms surface coatings rather than confined one-dimensional structures. In situ electron beam irradiation demonstrates the superior structural stability of single-walled CrI3 confined within MWCNTs, while externally coated CrI3 undergoes decomposition into metallic Cr clusters. Prolonged irradiation induces a morphological transformation of CrI3 nanotubes into nanorods. These insights lay the groundwork for engineering robust, tunable 1D
magnetic heterostructures of CrI3 for spintronic and data storage applications.
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Statistical Mechanics
Full Eigenstate Thermalization in Integrable Spin Systems
Tanay Pathak
The Eigenstate Thermalization Hypothesis (ETH) is a standard tool to understand the thermalization properties of an isolated
quantum system. Its generalization to higher order correlations of
matrix elements of local operators, dubbed the full ETH, relates the ETH free cumulants to the corresponding thermal free cumulants in the thermodynamic limit. In this work, we numerically test the full ETH predictions using exact diagonalization of two integrable
spin models: the Ising and the XXZ Heisenberg models. The differences from the behavior predicted by full ETH in chaotic systems are highlighted and contrasted along the way. We further study the out-of-time-ordered correlator (OTOC) through its approximate decomposition into contributions involving the second- and fourth-order ETH free cumulants. We find that, although the fourth-order contribution governs the late-time behavior of the OTOC in these integrable models, its dynamics differs significantly from that found in nonintegrable systems.
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Soft Condensed Matter
Dynamics of Choline Chloride based Deep Eutectic Solvents: Neutron Scattering Study
Rinesh T., H. Srinivasan, V.K. Sharma et al. (+1 more)
In this study, we investigate the microscopic
diffusion dynamics of choline chloride (ChCl) based deep eutectic solvents (DESs) to elucidate the influence of hydrogen bond donor (HBD) identity on the mobility of cholinium ions. The DES systems examined include ethaline, glyceline, and reline, comprising ChCl mixed with ethylene glycol, glycerol, and urea, respectively, in a 1:2 molar ratio. Quasielastic
neutron scattering experiments was used to probe the self-
diffusion of cholinium ions at molecular length and time scales. The dynamics were modelled as a combination of jump
diffusion of the molecular center of mass and localized translation within transient hydrogen-bond cages. Among the three systems, ethaline consistently exhibited the highest cholinium self-
diffusion coefficients across all investigated temperatures, attributed to shorter residence times and more frequent molecular jumps. In contrast, reline displayed longer residence times with significantly larger jump length, leading to a temperature-dependent dynamical crossover: While reline and glyceline exhibited comparable diffusivities at low temperatures, reline surpassed glyceline above 330 K. These findings highlight the crucial role of HBD identity in modulating microscopic
diffusion and provide valuable molecular-level insights for the rational design of DESs for targeted applications.
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All authors Rinesh T., H. Srinivasan, V.K. Sharma, S. Mitra
Mesoscale and Nanoscale Physics
Measurement of the Quantum Capacitance Between Two Metallic Electrodes
T. de Ara, B. Olivera, C. Sabater et al. (+1 more)
Two factors contribute to the electrical capacitance between two electrodes: a classical contribution, stemming from the electric field, and a
quantum contribution, governed by the Pauli exclusion principle, which increases the difficulty of adding charge to the electrodes. In metals, the high electronic Density of States (DOS) at the
Fermi energy allows the
quantum contribution to be neglected, and a classical description of the electrical capacitance between two metallic electrodes is normally used. Here, we study the
evolution of the capacitance as two metallic electrodes (Pt or Au) are approached to the limit when
quantum corrections are needed, before contact formation. At small distances, we observe that the classical increase in capacitance turns into saturation as the electrodes are approached, reaching the
quantum capacitance limit. Finally, a capacitance leakage due to
quantum tunneling is observed. Since the
quantum capacitance depends on the electronic DOS on the surface of the electrodes, we use it to probe the DOS change induced by molecular adsorption (Toluene) on the metallic surface.
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All authors T. de Ara, B. Olivera, C. Sabater, C. Untiedt
Strongly Correlated Electrons · Cross-listed from hep-th
Hayden–Preskill Model via Local Quenches
Weibo Mao and Tadashi Takayanagi
We model the Hayden–Preskill (HP) information recovery protocol in 2d CFTs via local joining quenches. Euclidean path integrals with slits prepare the HP subsystems: the message $M$, its reference $N$, the Page-time black hole $B$, the early radiation $E$, and the late radiation $R$; the remaining black hole after emitting $R$ is denoted as $B'$. The single-slit geometry provides an analytically tractable toy model, while the bounded-slit geometry more closely captures the HP setup. In the free Dirac
fermion 2d CFT, the mutual information $I(N\!:\!B')$ shows quasi-particle dynamics with partial or full revivals, whereas that in
holographic 2d CFTs, which are expected to be maximally chaotic, exhibit sharp transitions: in the bounded-slit case, when the size of the late radiation becomes comparable to that of the reference $N$, $I(N\!:\!B')$ does vanish at late time, otherwise it remains finite. This contrast between free CFTs and
holographic CFTs gives a clear characterization of the HP recovery threshold.
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Mesoscale and Nanoscale Physics
Giant and robust Josephson diode effect in multiband topological nanowires
Bao-Zong Wang, Zi-Kai Li, Zhong-Da Li et al. (+1 more)
We theoretically predict the
giant and robust Josephson diode effect in quasi-one-dimensional topological Majorana nanowires in the regime with multiple subbands, which is expected to be relevant for the real experiment. In the multiband regime, the Majorana bound states and conventional Andreev bound states can naturally coexist, and respectively contribute to the fractional and conventional parts in the Josephson effect, with the former/latter having 4$\pi$/2$\pi$-periodicity. We show that the interplay between the two types of bound modes can produce a robust and
giant diode effect in the deep topological phase regime. Notably, we unveil a novel
spin parity exchange mechanism, occurring only in the multiband regime, which leads to a robust high efficiency plateau of the
giant diode effect. This effect is a nontrivial consequence of the balanced
Fermi moment shifts of the multiple subbands in tuning the external
magnetic field. Our finding highlights the subband engineering as a powerful tool to optimize the Josephson diode effect realistically and provides a new feasible signature to identify topological phase regime in superconducting nanowires.
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All authors Bao-Zong Wang, Zi-Kai Li, Zhong-Da Li, Xiong-Jun Liu
Quantum Gases · Cross-listed from physics.atom-ph
All-optical bubble trap for ultracold atoms in microgravity
Romain Veyron, Clément Métayer, Jean-Baptiste Gérent et al. (+5 more)
In this paper, we present an all-optical method to produce shell-shaped traps for ultracold atoms in microgravity. Our scheme exploits optical double dressing of the ground state to create a short range strongly repulsive central potential barrier. Combined with a long range attractive central potential, this barrier forms the shell trap. We demonstrate that a pure spherical bubble, reaching the quasi 2D regime for standard atom numbers, could be formed from two crossed beams with a
parabolic profile. An analytical study shows that the relevant characteristics of the trap depend on the ratio of the ground and excited state polarisabilities and the lifetime of the excited state. As a
benchmark, we provide quantitative analysis of a realistic configuration for rubidium ensembles, leading to a 250 Hz transverse confinement for a 35 $\mu$m radius bubble and a trap residual scattering rate of less than 10 s$^{-1}$.
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All authors Romain Veyron, Clément Métayer, Jean-Baptiste Gérent, Ruiyang Huang, Eliott Beraud, Barry M. Garraway, Simon Bernon, Baptiste Battelier
Superconductivity
Signatures of superconducting Higgs mode in irradiated Josephson junctions
Aritra Lahiri, Juan Carlos Cuevas and Björn Trauzettel
The
Higgs mode, originally proposed in the context of superconductivity, corresponds to oscillations of the amplitude of the superconducting order parameter. Recent THz-domain optical studies have found signatures consistent with the
Higgs mode, but its unambiguous detection is still challenging. We predict that the existence of the
Higgs mode can be unambiguously revealed by standard measurements of the transport characteristics in microwave-irradiated asymmetric and transparent Josephson junctions. One signature of the
Higgs mode in a Josephson junction is the microwave-induced enhancement of the second harmonic of the
equilibrium current-phase relation (at zero DC bias voltage), whose sign differs from its expected value in the absence of the
Higgs mode. As the radiation frequency is varied, this enhancement exhibits resonant behavior when the microwave frequency is tuned across the
Higgs mass. The second signature that we propose is the enhancement of the second harmonic of the AC Josephson current at finite DC voltage bias, which can be probed in a customary analysis of the Shapiro steps in a microwave-irradiated junction.
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Statistical Mechanics · Cross-listed from hep-th
Six loop critical exponent analysis for Lee-Yang and percolation theory
J.A. Gracey
Using the recent six loop renormalization group functions for Lee-Yang and percolation theory constructed by Schnetz from a scalar cubic Lagrangian, we deduce the $\epsilon$ expansion of the critical exponents for both cases. Estimates for the exponents in three, four and five dimensions are extracted using two-sided Padé approximants and shown to be compatible with values from other approaches.
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Strongly Correlated Electrons
Liquid-gas analog multicriticality in a frustrated Ising bilayer
Yuchen Fan
We report the discovery of a multicritical point that extends the
liquid-gas paradigm to systems with competing
symmetry-breaking orders. Using large-scale Monte Carlo simulations of a frustrated
bilayer Ising antiferromagnet with tunable couplings, we map out a rich finite-temperature phase diagram hosting three ordered phases separated by both continuous and first-order transitions. By tuning the couplings, a tricritical line and a critical end-point line converge into a single multicritical line. At all points along the multicritical line,
symmetry-distinct phases exhibit identical leading critical behavior – consistent with the tricritical Ising universality class – while the subleading exponent exhibits a sharp shift from $y_g = 0.8$ to $y_g = 1$. This shift reflects an emergent $Z_2$
symmetry akin to that of the
liquid-gas critical point, but realized here at a genuine multicritical point involving simultaneous microscopic
symmetry breaking. Our results establish a universality scenario in which emergent
symmetry preserves the leading class but reorganizes subleading scaling, providing a general mechanism for
symmetry-enforced multicriticality.
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Mesoscale and Nanoscale Physics
Valley-dependent topological interface states in biased armchair nanoribbons of gapless single-layer graphene for transport applications
Zheng-Han Huang, Jing-Yuan Lai and Yu-Shu G. Wu
Valley-dependent topological physics offers a promising avenue for designing nanoscale devices based on gapless single-layer
graphene. To demonstrate this potential, we investigate an electrical bias-controlled topological discontinuity in valley polarization within a two-segment armchair nanoribbon of gapless single-layer
graphene. This discontinuity is created at the interface by applying opposite in-plane, transverse electrical biases to the two segments. An efficient tight-binding theoretical formulation is developed to calculate electron states in the structure. In a reference configuration, we obtain energy
eigenvalues and probability distributions that feature interface-confined electron eigenstates induced by the topological discontinuity. Moreover, to elucidate the implications of interface confinement for electron transport, a modified configuration is introduced to transform the eigenstates into transport-active, quasi-localized ones. We show that such states result in Fano "anti-resonances" in transmission spectra. The resilience of these quasi-localized states and their associated Fano fingerprints is examined with respect to fluctuations. Finally, a proof-of-concept band-stop electron energy filter is presented, highlighting the potential of this confinement mechanism and, more broadly, valley-dependent topological physics in designing nanoscale devices in gapless single-layer
graphene.
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Statistical Mechanics · Cross-listed from math.PR
Emergence of metastability on the hyperbolic lattice: Effects of boundary conditions
Vanessa Jacquier and Wioletta M. Ruszel
We investigate the Ising model on finite subgraphs of the
hyperbolic lattice under minus boundary conditions and in the presence of a positive external field $h$. Interpreting the boundary as frozen or cold wall conditions, we show that, for small values of $h$, the system exhibits metastable behaviour. Our result is very surprising, since non-amenable graphs, such as
hyperbolic lattices, feature exponentially growing boundaries, which typically destabilize local energy minima. In particular, we identify the unique metastable state and characterize the exit time from it. Furthermore, we establish asymptotic results for the distribution of the first hitting time and provide estimates for the spectral gap. Finally, we analyze the energy landscape and describe the nucleation mechanism for values of $h$ outside the metastable regime.
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Statistical Mechanics · Cross-listed from quant-ph
Recovery of the second law in fully quantum thermodynamics
Naoto Shiraishi and Ryuji Takagi
Quantum thermodynamics investigates how robust the second law of thermodynamics serves as the unique fundamental law in the small
quantum world. To tackle this problem, the
quantum coherence constitutes a major difficulty of investigations, which provides severe constraints hindering the recovery of a single thermodynamic potential. Here we solve this long-standing problem of
quantum information theory by revealing that the state convertibility under thermal operations is fully characterized by the second law of thermodynamics. Specifically, we prove that whether a
quantum state with
quantum coherence is convertible to another by a thermal operation with a correlated catalyst is completely determined by the free energy ordering. Unlike previous attempts, our setting does not resort to any additional external coherent assist, providing a faithful operational characterization of thermodynamic state transformation.
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Materials Science
From High-Entropy Ceramics (HECs) to Compositionally Complex Ceramics (CCCs) and Beyond
Jian Luo
Over the past decade, the field of high-
entropy ceramics (HECs) has expanded rapidly to encompass a broad range of
oxides, borides, silicides, and other ceramic solid solutions. In 2020, we proposed extending HECs to compositionally complex ceramics (CCCs), where non-equimolar compositions and the presence of long- or short-range order, although reducing configurational
entropy, create new opportunities to tailor and enhance properties, often surpassing those of higher-
entropy counterparts. Along these lines, several fundamental scientific questions arise. Is the
entropy in HECs truly high? Is maximizing
entropy always desirable? In this perspective article, I revisit key concepts and terminologies and highlight emerging directions, including dual-phase CCCs, ultrahigh-
entropy phases, and novel processing routes such as ultrafast reactive sintering. I propose that exploring compositional complexity across vast non-equimolar spaces, together with exploiting correlated disorder (coupled chemical and structural short-range order), represents a transformative strategy for designing ceramics with superior performance.
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Mesoscale and Nanoscale Physics
Engineering Magnetic States and Magnetoresistance in Bisegmented Co-Ni Jellyfish Nanowires via Interplay of Shape and Magnetocrystalline Anisotropies
M.I. Sobirov, K.A. Rogachev, M.A. Bazrov et al. (+9 more)
Expanding the spectrum of 3D
magnetic nanostructures requires mastering the interplay between different anisotropy contributions. Here, we fabricate bisegmented jellyfish nanowires with tailored arrangements of Co (strong magnetocrystalline anisotropy) and Ni (dominant shape anisotropy) segments. We uncover a unique
magnetic duality: Co segments can be tuned to exhibit either a flux-closing multidomain state or a shape-anisotropy-dominated
vortex configuration, directly governed by their geometry. This local domain structure, imaged by MFM and simulated micromagnetically, dictates the global
magnetic response-suppressing magnetostatic interactions in arrays and enabling the programming of the anisotropic magnetoresistance (AMR) in single nanowires. Our work provides a blueprint for designing functional
magnetic nanomaterials where magnetoresistive properties are engineered through strategic anisotropy control.
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All authors M.I. Sobirov, K.A. Rogachev, M.A. Bazrov, Zh. Zh. Namsaraev, I.M. Sapovskii, T.R. Rakhmatullaev, N.V. Ilin, A.O Lembikov, S.M. Pisarev, A.V. Ognev, A.S. Samardak, A.Yu. Samardak
Disordered Systems and Neural Networks · Cross-listed from physics.app-ph
Field Free Spin-Orbit Torque Controlled Synapse and Stochastic Neuron Devices for Spintronic Boltzmann Neural Networks
Aijaz H. Lone, Meng Tang, Camelia Florica et al. (+4 more)
Spintronics offers a promising approach to energy efficient neuromorphic computing by integrating the functionalities of synapses and
neurons within a single platform. A major challenge, however, is achieving field-free
spin orbit torque SOT control over both synaptic and neuronal devices using an industry-adopted spintronic materials stack. In this study, we present field-free SOT spintronic synapses utilizing a CoFeB
ferromagnetic thin film system, where asymmetrical device design and specifically added lateral notches in the CoFeB thin film facilitate effective domain wall DW nucleation, movement, and pinning and depinning. This method yields multiple analog, nonvolatile resistance states with enhanced linearity and
symmetry, resulting in programmable and stable synaptic weights. We provide a systematic measurement approach to improve the linearity and
symmetry of the synapses. Additionally, we demonstrate nanoscale
magnetic tunnel junctions MTJs that function as SOT-driven
stochastic neurons, exhibiting current-tunable, Boltzmann-like probabilistic switching behavior, which provides an intrinsic in-hardware Gibbs sampling capability. By integrating these synapses and
neurons into a Boltzmann machine complemented by a classifier layer, we achieve recognition accuracies greater than 98 percent on the MNIST
dataset and 86 percent on Fashion MNIST. This work establishes a framework for field free synaptic and neuronal devices, setting the stage for practical, materials-compatible, and all spintronic neuromorphic computing hardware.
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All authors Aijaz H. Lone, Meng Tang, Camelia Florica, Bin He, Jingkai Xu, Xixiang Zhang, Gianluca Setti
Materials Science
Co-evaporated Formamidinium tin triiodide with suppressed p-type self-doping
Junhyoung Park, Andrea Olivati, Mirko Prato et al. (+2 more)
Co-evaporation of formamidinium tin triiodide (FASnI3) precursors, without any additives or reducing
agents, leads to the growth of a highly crystalline thin film which shows a bandgap around 1.31 eV, closely matching the theoretical value predicted from the ideal single
crystal structure of FASnI3. The polycrystalline thin film presents a lower tendency of Sn2+ to Sn4+ oxidation and highly reduced tendency to self-doping, demonstrating, overall, an improved resistance to defects formation. These findings suggest solvent-free co-evaporation processes as a promising route for high quality Sn-based perovskite polycrystalline thin films.
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All authors Junhyoung Park, Andrea Olivati, Mirko Prato, Min Kim, Annamaria Petrozza
Mesoscale and Nanoscale Physics
Probing orbital currents through inverse orbital Hall and Rashba effects
E. Santos, J. L. Costa, R.L. Rodriguez-Suarez et al. (+2 more)
We report a comprehensive experimental investigation of orbital-to-charge conversion in metallic and
semiconductor materials, emphasizing the fundamental roles of the inverse orbital
Hall effect (IOHE) and the inverse orbital Rashba effect. Using
spin pumping driven by
ferromagnetic resonance (SP-FMR) and the
spin Seebeck effect (SSE), we demonstrate efficient orbital current generation and detection in YIG/Pt/NM structures, where NM is either a metal or a
semiconductor. A central finding is the dominance of orbital contributions over
spin-related effects, even in systems with weak
spin-orbit coupling. In particular, a large enhancement of the SP-FMR and SSE signals is observed in the presence of naturally oxidized Cu in different
heterostructures. Furthermore, we identify positive and negative IOHE signals in Ti and Ge, respectively, and extract orbital
diffusion lengths in both systems using a diffusive model. Our results confirm the presence of orbital transport and offer valuable insights that may guide the further development of orbitronics.
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All authors E. Santos, J. L. Costa, R.L. Rodriguez-Suarez, J. B. S. Mendes, A. Azevedo
Soft Condensed Matter
Memory behavior of a randomly driven model glass
Roni Chatterjee, Smarajit Karmakar, Muhittin Mungan et al. (+1 more)
We investigate by atomistic simulations the
memory behavior a model glass subjected to random driving protocols. The training consists of a random walk of forward and/or backward shearing sequences bounded by a maximal shear strain of absolute value {\gamma}T . We show that such a
stochastic training protocol is able to record the training amplitude. Different read-out protocols are also tested and are shown to be able to retrieve the training amplitude. We then emphasize the ten- sorial character of the
memory encoded in the glass sample and then characterize the anisotropic mechanical behavior of the trained samples.
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All authors Roni Chatterjee, Smarajit Karmakar, Muhittin Mungan, Damien Vandembroucq
Statistical Mechanics · Cross-listed from math.PR
The odometer in subcritical activated random walk
Tobias Johnson and Jacob Richey
We consider the activated random walk particle system, a model of self-organized criticality, on $\mathbb{Z}$ with i.i.d.-Bernoulli initial configuration. We show that at subcritical density, the system's odometer function, which counts the number of actions taken at each site, has a stretched exponential tail. It follows that the expected odometer at each site is finite.
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Other Condensed Matter
Spin Group Symmetry Criteria for Odd-parity Magnets
Xun-Jiang Luo, Jin-Xin Hu, Meng-Li Hu et al. (+1 more)
Odd-parity magnets (OPMs) have recently emerged as a new
magnetic class, but their general
symmetry criteria remain elusive. In this Letter, we establish these criteria through a comprehensive
spin group
symmetry analysis. Concretely, we identify eight distinct
symmetry-driven cases that support OPMs with collinear, coplanar, or noncoplanar
magnetic order. These are classified into three classes based on their
spin textures: collinear (type-I), coplanar (type-II), and noncoplanar (type-III). From the Magndata database, we identify 33 candidate OPM materials and diagnose their
spin-splitting character ($p$- or $f$-wave) by analyzing the representation of
spin textures within an emergent Laue group derived from the
spin space group, which reveals a variety of novel
spin textures. To validate the
symmetry criteria, we construct and analyze two theoretical models. Furthermore, we demonstrate that OPMs can host an intrinsic $\mathbb{Z}_2$
topology and propose a model for their realization. Our work provides a foundational framework for the future exploration of OPMs.
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All authors Xun-Jiang Luo, Jin-Xin Hu, Meng-Li Hu, K. T. Law