Superconductivity
Effect of Underlayer Induced Charge Carrier Substitution on the Superconductivity of Ti40V60 Alloy Thin Films
Shekhar Chandra Pandey, Shilpam Sharma, Pooja Gupta et al. (+2 more)
The influence of metallic and semiconducting (V, Al, and Si) under-layer induced charge carrier substitution on the superconducting properties of the Ti40V60
alloy thin films are studied and also compared with a pristine reference film without any under-layer. All the films exhibit metallic behavior in the normal state and a superconducting transition at low temperatures, where the superconducting transition temperature is tunable between 4.77 K and 5.73 K.
Hall measurements on the films reveal that the under-layer strongly affects the charge carrier type and density, leading to a correlation between increasing carrier concentration and decreasing TC. The Si under-layer introduces the highest disorder, yet yields the highest TC. This indicates that in the Ti40V60
alloys, a moderate amount of disorder suppresses the
spin-fluctuations (inherent to the
alloy system) induced pair breaking, thereby enhancing the superconductivity. The comparable TC of the film with V under-layer and the film without under-layer, and the much smaller coherence length (~6.2 nm) as compared to the film thickness (25 nm), confirm the absence of any significant proximity effects. These findings demonstrate that under-layer engineering provides an effective route to tune the superconducting properties of Ti-V
alloy thin films.
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All authors Shekhar Chandra Pandey, Shilpam Sharma, Pooja Gupta, L. S. Sharath Chandra, M.K. Chattopadhyay
Materials Science
Magnetoelastic honeycomb fragmentation in VI$_{3}$
Enlin Shen, Tiberiu I. Popescu, Nishwal Gora et al. (+9 more)
The discovery of ordered magnetism in two-dimensional van der Waals materials at the monolayer limit challenges the Mermin-Wagner
theorem, which forbids spontaneous breaking of continuous
symmetries in two dimensions at finite temperatures. The persistence of static magnetism in low-dimensions is fundamentally influenced by
magnetic anisotropy and the local single-ion crystalline electric field. Crucially,
spin-orbit coupling connects the structural properties with
spin degrees of freedom. We investigate the
magnetic single-ion properties in the van der Waals magnet VI$_3$. Utilizing
neutron and x-ray diffraction, we map out the
symmetry breaking phase transitions and argue for a single structural transition at T$_S \sim$ 80 K, driven by an orbital degeneracy, followed by a
ferromagnetic transition at a lower temperature, T$_C \sim$ 50 K. Through a comparative analysis of samples prepared under varying conditions, we suggest that lower temperature transitions reported near $\sim$ 30 K are not intrinsic to VI$_{3}$. A group theoretical analysis suggests a structural transition from rhombohedral $R\overline{3}$ to triclinic $P\overline{1}$ or $P1$. This transition is significant as it suggests the formation of two distinct crystallographyically inequivalent V$^{3+}$ sites, each with distinct
spin-orbital properties.
Neutron spectroscopy provides evidence for dominant
magnetic exchange coupling only between
symmetry-equivalent sites in the triclinc unit
cell. We suggest this breaks up the low-temperature honeycomb VI$_3$
lattice into two interpenetrating approximately hexagonal planes resulting in a fragmentated honeycomb. Our findings highlight the critical role of magnetoelastic coupling in determining the
magnetic and structural phases in two-dimensional van der Waals magnets.
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All authors Enlin Shen, Tiberiu I. Popescu, Nishwal Gora, Guratinder Kaur, Edmond Chan, Harry Lane, Jose A. Rodriguez-Rivera, Guangyong Xu, Peter M. Gehring, Russell A. Ewings, Andy N. Fitch, Chris Stock
Mesoscale and Nanoscale Physics
High-quality and field resilient microwave resonators on Ge/SiGe quantum well heterostructures
Luigi Ruggiero, Carlo Ciacca, Pauline Drexler et al. (+5 more)
Superconducting resonators integrated with Ge
quantum wells (QWs) offer a promising platform for hybrid
quantum devices. Yet, in the most common
heterostructure architectures, they have so far been limited by sizable
photon losses. Here, we report the fabrication and characterization of microwave resonators patterned in the Al thin film of an in-situ grown
superconductor/
semiconductor hybrid
heterostructure (HS). The
semiconductor part of this hybrid HS is grown on a commercial Ge substrate. We consistently achieve internal quality factors $Q_i>1000$, surpassing previous results on Ge QW
heterostructures grown using the concept of a virtual Ge substrate on Si substrates. We reach $Q_i \approx 49000$ at single-
photon occupation and a plateau of $Q_i \approx 20000$ at sub-one
photon, an order of magnitude larger than any previously reported value of resonators on Ge QW structures at low power. We further characterize the thin Al film forming the resonator, extracting its kinetic inductance and superconducting gap, and studying its
magnetic field dependence. Notably, the resonance remains well-defined up to in-plane
magnetic fields of 850 mT. A hysteresis emerges in the out-of-plane
magnetic field dependence, for both the resonance frequency and the quality factor, indicating an interesting interplay between
vortex- and quasiparticle loss mechanisms.
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All authors Luigi Ruggiero, Carlo Ciacca, Pauline Drexler, Vera Jo Weibel, Christian Olsen, Christian Schönenberger, Dominique Bougeard, Andrea Hofmann
Materials Science
Benchmarking Universal Machine Learning Interatomic Potentials on Elemental Systems
Hossein Tahmasbi, Andreas Knüpfer, Thomas D. Kühne et al. (+1 more)
The rapid emergence of universal Machine Learning Interatomic Potentials (uMLIPs) has transformed materials modeling. However, a comprehensive understanding of their generalization behavior across configurational space remains an open challenge. In this work, we introduce a benchmarking framework to evaluate both the
equilibrium and far-from-
equilibrium performance of state-of-the-art uMLIPs, including three MACE-based models, MatterSim, and PET-MAD. Our assessment utilizes Equation-of-State (EOS) tests to evaluate near-
equilibrium properties, such as bulk
moduli and
equilibrium volumes, alongside extensive Minima Hopping (MH) structural searches to probe the global Potential Energy Surface (PES). Here, we assess universality within the fundamental limit of unary (elemental) systems, which serve as a necessary baseline for broader chemical generalization and provide a framework that can be systematically extended to multicomponent materials. We find that while most models exhibit high accuracy in reproducing
equilibrium volumes for transition metals, significant performance gaps emerge in alkali and alkaline earth metal groups. Crucially, our MH results reveal a decoupling between search efficiency and structural fidelity, highlighting that smoother learned PESs do not necessarily yield more accurate energetic landscapes.
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All authors Hossein Tahmasbi, Andreas Knüpfer, Thomas D. Kühne, Hossein Mirhosseini
Superconductivity
Composition-Based Machine Learning for Screening Superconducting Ternary Hydrides from a Curated Dataset
Kazuaki Tokuyama, Souta Miyamoto, Taichi Masuda et al. (+1 more)
We present an ensemble machine-learning approach for composition-based, structure-agnostic screening of candidate
superconductors among ternary hydrides under high pressure. Hydrogen-rich hydrides are known to exhibit high superconducting transition temperatures, and ternary or multinary hydrides can stabilize superconducting phases at reduced pressures through chemical compression. To systematically explore this vast compositional space, we construct an ensemble of 30 XGBoost regression models trained on a curated
dataset of approximately 2000 binary and ternary hydride entries. The model ensemble is used to screen a broad set of A-B-H compositions at pressures of 100, 200, and 300 GPa, with screening outcomes evaluated statistically based on prediction consistency across ensemble members. This analysis highlights several high-scoring compositional systems, including Ca-Ti-H, Li-K-H, and Na-Mg-H, which were not explicitly included in the training
dataset. In addition, feature-importance analysis indicates that elemental properties such as ionization energy and atomic radius contribute significantly to the learned composition-level trends in superconducting transition temperature. Overall, these results demonstrate the utility of ensemble-based machine learning as a primary screening tool for identifying promising regions of chemical space in superconducting hydrides.
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All authors Kazuaki Tokuyama, Souta Miyamoto, Taichi Masuda, Katsuaki Tanabe
Statistical Mechanics · Cross-listed from quant-ph
Tree tensor network states represent low-energy states faithfully
Thomas Barthel
Extending corresponding results for
matrix product states [Verstraete and Cirac, PRB 73, 094423 (2006); Schuch et al. PRL 100, 030504 (2008)], it is shown how the approximation error of tree tensor network states (TTNS) can be bounded using Schmidt spectra or Rényi
entanglement entropies of the target
quantum state. Conversely, one obtains bounds on TTNS bond dimensions needed to achieve a specific approximation accuracy. The result implies that efficient TTNS approximations exist if $\alpha<1$ Rényi
entanglement entropies for single-branch cuts obey an area law, as in ground and low-energy states of certain gapped systems on tree graphs.
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Strongly Correlated Electrons
Unveiling the Phase Diagram and Nonlinear Optical Responses of a Twisted Kitaev Chain
Ya-Min Quan, Shi-Qing Jia, Xiang-Long Yu et al. (+2 more)
Detecting Kitaev interactions in real materials remains challenge, as conventional experimental techniques often have difficulty distinguishing fractionalized excitations from other normal contributions. Terahertz two-dimensional coherent spectroscopy (2DCS) offers a novel approach for probing many-body phenomena, such as exotic excitations in
quantum magnets. Motivated by recent experiments on CoNb$_2$O$_6$ and the development of the terahertz spectroscopy in Kitaev
quantum spin liquid, we proposed a twisted Kitaev model for CoNb$_2$O$_6$ and determined the precise twist angle according to experimental specific-heat phase diagram. With this calibrated model, we found that non-rephasing diagonal and rephasing anti-diagonal signals appear in the 2DCS nonlinear response. The $x$ and $y$ components of the
spin superexchange interactions split the rephasing signals into a grid of discrete peaks. We further demonstrate that the diagonal and the discrete rephasing signals primarily originate from two-spinon and four-spinon excitation processes based on numerical projection method. These findings indicate that even weak Kitaev interactions in
quantum materials can be effectively detected via two-dimensional coherent spectroscopy .
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All authors Ya-Min Quan, Shi-Qing Jia, Xiang-Long Yu, Hai-Qing Lin, Liang-Jian Zou
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Deterministic exciton confinement in 2D semiconductors via local dielectric engineering for scalable quantum light sources
Raziel Itzhak, Alex Hayat and Ilya Goykhman
Single-
photon emitters are essential building blocks for
quantum communication and photonic
quantum technologies. However, realizing scalable, on-chip SPEs on a CMOS-compatible platform remains a significant challenge. Here, we propose and theoretically demonstrate a scalable approach to
exciton confinement in two-dimensional
semiconductors via local dielectric engineering. By introducing a high-dielectric-constant nanopillar above or beneath the 2D material, we create a spatially varying dielectric environment that can support localized
exciton states, enabling deterministic, lithography-compatible single-
photon emission without relying on strain, defects, or etching of the 2D layer. Using numerical solutions to the 2D excitonic Schrodinger equation, we quantify the resulting confinement through binding energies, wavefunction profiles, and a spatial confinement parameter. These results offer a practical and scalable route for integrating 2D-based
quantum emitters into photonic platforms, paving the way for next-generation
quantum optoelectronic devices.
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Superconductivity
A Symmetric Superconducting Dome Hosts Non-Fermi Liquid Behavior at Optimal Doping in MoS2
Qiao Chen, Chengyu Yan, Dino Novko et al. (+9 more)
The similarities between the phase diagrams of ionic
liquid-gated transition metal dichalcogenides (TMDCs) and high-temperature
superconductors have garnered considerable interest due to the presence of a superconducting dome with a non-monotonic dependence of the superconducting order parameter as a function of charge carrier density. However, the lack of a complete superconducting dome and insights into the normal state in ionic
liquid-gated TMDCs prevents a detailed mapping between the two systems. In this work, we obtain a symmetric superconducting dome that extends from deep underdoped regime all the way to deep overdoped regime in ionic
liquid gated MoS2 with a refined gating protocol. We demonstrate that the dome is anticorrelated with the
evolution of non-
Fermi liquid behavior in the normal states. The scattering rate in the non-
Fermi liquid regime can reach Planckian limit. The results may shed light on the emergence of superconductivity in TMDCs.
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All authors Qiao Chen, Chengyu Yan, Dino Novko, Changshuai Lan, Huiqin Jian, Yi Yan, Xinming Zhao, Yihang Li, Huai Guan, Bo Gao, Zhong Wan, Shun Wang
Soft Condensed Matter
Active Brownian particles in power-law viscoelastic media
David Santiago Quevedo, Monica Conte, Marjolein Dijkstra et al. (+1 more)
Many active particles are embedded in environments that exhibit viscoelastic properties. An important class of such media lacks a single characteristic relaxation timescale when subjected to a time-dependent stress. Rather, the stress response spans a broad continuum of timescales, a behavior naturally described by a scale-free, fractal-like power-law relaxation modulus. Using a generalization of the fractional Langevin equation, we investigate an active Brownian particle embedded in a power-law viscoelastic environment with translational and rotational dynamics governed by independent fractional orders. We solve the model analytically, develop a numerical scheme to validate the theoretical predictions, and provide tools that can be used in further studies. A rich variety of
diffusion regimes emerges, which modify the intermediate-time behavior of the mean squared displacement. Notably, we find that the competition between translational and rotational contributions favors a superdiffusive persistence over the standard ballistic motion, and over-stretches its characteristic timescale, fundamentally altering the standard relation between persistence and propulsion in active matter.
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All authors David Santiago Quevedo, Monica Conte, Marjolein Dijkstra, Cristiane Morais Smith
Materials Science
Turing Pattern Engineering Enables Kinetically Ultrastable yet Ductile Metallic Glasses
Huanrong Liu, Qingan Li, Shan Zhang et al. (+3 more)
Enhancing the kinetic stability of glasses often necessitates deepening thermodynamic stability, which typically compromises ductility due to increased structural
rigidity. Decoupling these properties remains a critical challenge for functional applications. Here, we demonstrate that pattern engineering in metallic glasses (MGs) enables unprecedented kinetic ultrastability while retaining thermodynamic metastability and intrinsic plasticity. Through atomistic simulations guided by machine-learning interatomic potentials and replica-exchange molecular dynamics, we reveal that clustering oxygen contents, driven by reaction-
diffusion-coupled pattern dynamics, act as localized pinning sites. These motifs drastically slow structural relaxation, yielding kinetic stability comparable to
crystal-like ultrastable glasses while retaining an energetic as-cast state. Remarkably, the thermodynamically metastable state preserves heterogeneous atomic mobility, allowing strain delocalization under mechanical stress. By tailoring oxygen modulation via
geometric patterning, we achieve an approximately 200 K increase in the onset temperature of the glass transition (Tonset) while maintaining fracture toughness akin to conventional MGs. This work establishes a paradigm of kinetic stabilization without thermodynamic compromise, offering a roadmap to additively manufacture bulk amorphous materials with combined hyperstability and plasticity.
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All authors Huanrong Liu, Qingan Li, Shan Zhang, Rui Su, Yunjiang Wang, Pengfei Guan
Quantum Gases · Cross-listed from quant-ph
Disorder-induced broadening of quantum momentum distribution
Vili Heinonen and Jani Lukkarinen
We study the long-time behavior of a non-interacting two-dimensional
quantum gas in a weak random potential with long-range correlations. Any peaked initial momentum distribution will eventually become isotropic and broaden due to scattering events with the random potential. We derive an expression for the long-time average of the momentum distribution and test it against computer simulations. We also discuss momentum isotropization and spatial
diffusion.
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Materials Science
Low temperature magneto-transport and magnetic properties of MnSb$_2$Te$_4$ single crystals
V.N. Zverev, N.A. Abdullayev, Z.S. Aliev et al. (+6 more)
The results of a comprehensive study of MnSb$_2$Te$_4$ single
crystals are presented. The structure, Raman spectra, low-temperature transport,
Hall effect, magnetization, and
magnetic susceptibility are studied. It was established that the
crystals are
ferromagnetic, with a Curie temperature ranging from 22 to 45\,K for different samples.
Hall and magnetization measurements demonstrated that the system is a soft ferromagnet, which is of interest for practical applications.
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All authors V.N. Zverev, N.A. Abdullayev, Z.S. Aliev, I.R. Amiraslanov, Z.A. Jahangirli, I.I. Klimovskikh, A.A. Rybkina, A.M. Shikin, N.T. Mamedov
Superconductivity
From Interdependent Networks to Two-Interactions Physical Systems
Yuval Sallem, Nahala Yadid, Xi Wang et al. (+5 more)
Recent advances have shown that introducing dependency interactions between two superconducting networks can trigger abrupt, hysteretic normal-
superconductor phase transitions. In this study, we demonstrate that such behavior can also arise in a single-network superconducting system that features two distinct types of interactions: short-range electrical connectivity and long-range thermal dependency. Using experimental and simulation methods, we show that when sufficient heat is dissipated within a single-layer disordered superconducting network, the system undergoes a mixed-order phase transition marked by both a discontinuous change in resistance and critical scaling behavior. We find that the emergence and characteristics of these abrupt transitions depend critically on the thermal conductivity of the underlying substrate, establishing heat flow as the origin of the unique phase transition. Additionally, both experimental and numerical results reveal long-lived transient states and scaling dynamics near the critical point, consistent with spontaneous branching processes observed in interdependent networks theory. These findings strongly demonstrate that complex critical phenomena, such as mixed-order transitions, previously attributed to structurally interdependent systems, can also arise within single-layer physical systems when dual interactions coexist. Our results broaden the scope of the theory and experiments of phase transitions in interdependent networks and suggest new ways to design and control phase changes in physical, biological, and technological systems where two interactions are present.
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All authors Yuval Sallem, Nahala Yadid, Xi Wang, Irina volotsenko, Bnaya Gross, Beena Kalisky, Shlomo Havlin, Aviad Frydman
Materials Science
Linking Thermal History to Shear Band Interaction and Macroscopic Ductility in Metallic Glasses
Lechuan Sun, Shan Zhang, Bin Xu et al. (+3 more)
Shear band propagation and interaction are critical to the mechanical performance of metallic glasses and are strongly governed by thermal history, yet their microscopic mechanisms remain unclear. Here, using molecular dynamics simulations combined with a state-of-the-art annealing protocol, we systematically investigate these behaviors in a model metallic glass across effective quenching rates spanning six orders of magnitude. Through a double-notch model, we show that the normalized interaction distance relative to the single shear band width is significantly larger in slowly quenched samples than in rapidly quenched ones. Atomic-scale analysis reveals that rapidly quenched samples exhibit a high density of pre-existing soft regions, which trigger correlated shear transformation zones through local
vortex fields, resulting in propagation path locking and weak inter-band coupling. In contrast, slowly quenched samples exhibit enhanced structural heterogeneity and a right-shifted activation energy spectrum, promoting a single large-scale
vortex field ahead of the shear band front. This field facilitates long-range stress transmission and induces shear band deflection, convergence, and coalescence, a transition resembling a "shielding effect" in fracture mechanics, where
vortex-mediated disturbances destabilize the advancing shear band front. Our findings establish a direct microscopic connection between glass stability and shear-band-mediated plasticity and suggest that regulating shear band interactions offers a promising route to enhance the room-temperature ductility of metallic glasses.
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All authors Lechuan Sun, Shan Zhang, Bin Xu, Rui Su, Yunjiang Wang, Pengfei Guan
Materials Science
Geometry, electronic structure, and optical properties of boron cages: A first-principles DFT study
Kashinath T. Chavan, Ihsan Boustani and Alok Shukla
A systematic study of the structural, electronic, and optical properties of cage-like boron clusters, with the number of constituent atoms ranging from 20 to 122, has been carried out within the framework of density-functional theory (DFT), employing 6-31G(d, p) extended basis set. The dynamic stability of the clusters is analyzed through the vibrational frequency analysis, while to study the thermodynamic stability, we computed their binding energies per atom. The results suggest that the 32- and 92-atom cages are the most stable among the small and the large structures. The optical absorption spectra of these cages is computed using the time-dependent densityfunctional theory (TDDFT), which suggests their applications in optoelectronic devices in the visible range of the spectrum.
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Materials Science
Multi-state electromagnetic phase modulations in NiCo2O4 through cation disorder and hydrogenation
Xuanchi Zhou, Xiaohui Yao, Shuang Li et al. (+5 more)
One focal challenge in engineering low-power and scalable all-
oxide spintronic devices lies in exploring
ferromagnetic oxide material with perpendicular
magnetic anisotropy (PMA) and electronic conductivity while exhibiting tunable
spin states. Targeting this need, spinel nickel cobaltite (NiCo2O4, NCO), featured by room-temperature ferrimagnetically metallic ground state with strong PMA, emerges as a promising candidate in the field of
oxide spintronics. The cation distribution disorder inherent to NCO renders competing electromagnetic states and abnormal sign reversal of anomalous
Hall effect (AHE), introducing an additional freedom to adjust electromagnetic transports. Here, we unveil multi-state electromagnetic phase modulations in NCO system through controllable cation disorder and
proton evolution, extensively expanding electromagnetic phase diagram. The cation disorder in NCO tunable by growth temperature is identified as a critical control parameter for kinetically adjusting the
proton evolution, giving rise to intermediate hydrogenated states with chemical stability. Hydrogen incorporation reversibly drives structural transformation and electromagnetic state evolutions in NCO, with rich
spin-dependent correlated physics uncovered by combining the AHE scaling relation and synchrotron-based spectroscopy. Our work not only establishes NCO as a versatile platform for discovering
spin-dependent physical functionality but also extends the horizons in materials design for state-of-the-art spintronic devices harnessing magneto-ionic control and inherent cation disorder.
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All authors Xuanchi Zhou, Xiaohui Yao, Shuang Li, Xiaomei Qiao, Jiahui Ji, Guowei Zhou, Huihui Ji, Xiaohong Xu
Materials Science
Gauge-Invariant Long-Wavelength TDDFT Without Empty States: From Polarizability to Kubo Conductivity Across Heterogeneous Materials
Christian Tantardini, Quentin Pitteloud, Boris Yakobson et al. (+1 more)
Electromagnetic response is commonly computed in two
languages: length-gauge molecular polarizabilities and velocity-gauge (Kubo) conductivities for periodic solids. We introduce a compact, gauge-invariant bridge that carries the same microscopic inputs-transition dipoles and interaction kernels-from molecules to
crystals and heterogeneous media, with explicit SI prefactors and fine-structure scaling via $(\alpha_{\rm fs})$. The long-wavelength limit is handled through a reduced dielectric
matrix that retains local-field mixing, interfaces and 2D layers are treated with sheet boundary conditions (rather than naïve ultrathin films), and length-velocity equivalence is enforced in practice by including the equal-time (diamagnetic/contact) term alongside the paramagnetic current. Finite temperature is addressed on the Matsubara axis with numerically stable real-axis evaluation (complex polarization propagator), preserving unit consistency end-to-end. The framework enables predictive, unit-faithful observables from
radio frequency to ultraviolet-RF/microwave heating and penetration depth, dielectric-logging contrast, interfacial optics of thin films and 2D sheets, and adsorption metrics via imaginary-axis polarizabilities. Numerical checks (gauge overlay and optical $(f)$-sum saturation) validate the implementation. Immediate priorities include compact, temperature- and salinity-aware kernels with quantified uncertainties and operando interfacial diagnostics for integration into multiphysics digital twins.
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All authors Christian Tantardini, Quentin Pitteloud, Boris Yakobson, Martin Andersson
Materials Science
Ultrahigh Charge-to-Spin Conversion and Tunneling Magnetoresistance in Quasi-Two-Dimensional d-wave Altermagnet
Qing Zhang, Siyun Wang, Jianting Dong et al. (+1 more)
The emergence of altermagnets has driven groundbreaking advances in spintronics. Notably, d-wave altermagnets support non-relativistic
spin transport, efficient charge-to-
spin conversion, and T-odd
spin currents. In addition, their integration as electrodes in
antiferromagnetic tunnel junctions (AFMTJs) enables a tunneling magnetoresistance (TMR) effect, allowing electrical detection of Néel vectors for next-generation
memory devices. In this work, we investigate the non-relativistic
spin transport properties of the quasi-two-dimensional (quasi-2D) d-wave altermagnet KV\textsubscript{2}Se\textsubscript{2}O and the TMR effect in KV\textsubscript{2}Se\textsubscript{2}O-based AFMTJs via first-principles calculations. Our results reveal that KV\textsubscript{2}Se\textsubscript{2}O exhibits a non-relativistic longitudinal
spin polarization and a
spin Hall angle both exceeding 60% at room temperature, while KV\textsubscript{2}Se\textsubscript{2}O-based AFMTJs achieve a
giant TMR reaching approximately $10^{12}$%, which remains robust against
Fermi level shifts. These findings highlight the anisotropic
spin polarization inherent to d-wave staggered magnetism and underscore the critical role of
Fermi surface
topology in enhancing T-odd
spin transport and the TMR effect in AFMTJs.
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All authors Qing Zhang, Siyun Wang, Jianting Dong, Jia Zhang
Materials Science
Dielectric and gate metal engineering for threshold voltage modulation in enhancement mode monolayer MoS2 field effect transistors
Lixin Liu, Han Yan, Leyi Loh et al. (+8 more)
Excellent gate electrostatics in field effect transistors (FETs) based on two-dimensional transition metal dichalcogenide (2D TMD) channels can dramatically decrease static power dissipation. Energy efficient FETs operate in enhancement mode with small and positive threshold voltage (Vth) for n-type devices. However, most state-of-the-art FETs based on monolayer MoS2 channel operate in depletion mode with negative Vth due to doping from the underlying dielectric substrate. In this work, we identify key properties of the
semiconductor/dielectric interface (MoS2 on industrially relevant high dielectric constant (k) HfO2, ZrO2 and hBN for reference) responsible for realizing enhancement-mode operation of 2D MoS2 channel FETs. We find that hBN and ZrO2 dielectric substrates provide low defect interfaces with MoS2 that enables effective modulation of the Vth using gate metals of different work functions (WFs). We use photoluminescence (PL) and synchrotron X-ray photoelectron spectroscopy (XPS) measurements to investigate doping levels in monolayer MoS2 on different dielectrics with different WF gate metals. We complement the FET and spectroscopic measurements with capacitance-voltage analysis on dielectrics with varying thicknesses, which confirm that Vth modulation in ZrO2 devices is correlated with WF of the gate metals - in contrast with HfO2 devices that exhibit signatures of Vth pinning induced by
oxide/interface defect states. Finally, we demonstrate FETs using a 2D MoS2 channel and a 6 nm of ZrO2 dielectric, achieving a subthreshold swing of 87 mV dec-1 and a threshold voltage of 0.1 V. Our results offer insights into the role of dielectric/
semiconductor interface in 2D MoS2 based FETs for realizing enhancement mode FETs and highlight the potential of ZrO2 as a scalable high-k dielectric.
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All authors Lixin Liu, Han Yan, Leyi Loh, Kamal Kumar Paul, Soumya Sarkar, Deepnarayan Biswas, Tien-Lin Lee, Takashi Taniguchi, Kenji Watanabe, Manish Chhowalla, Yan Wang
Materials Science
Microscopic and spectroscopic evidences for multiple ion-exchange reactions controlling biomineralization of CaO.MgO.2SiO2 nanoceramics
R. Vahedifard and E. Salahinejad
This study is focused on the mechanism of in vitro biomineralization on the surface of CaO.MgO.2SiO2 (diopside) nanostructured coatings by scanning electron microscopy, energy-dispersive X-ray spectroscopy and inductively coupled
plasma spectroscopy assessments. A homogeneous diopside coating of almost 2 um in thickness was deposited on a medical-grade stainless steel by coprecipitation, dipping and sintering sequences. After soaking the sample in a simulated body fluid (SBF) for 14 days, a layer with the thickness of 8 {\mu}m is recognized to be substituted for the primary diopside deposit, suggesting the mineralization of apatite on the surface. Investigations revealed that the newly-formed layer is predominantly composed of Ca, P and Si, albeit with a biased accumulations of P and Si towards the surface and substrate, respectively. The variations in the ionic composition and pH of the SBF due to the incubation of the sample were also correlated with the above-interpreted biomineralization. In conclusion, the multiple ion-exchange reactions related to Ca, Mg, Si and P were found to be responsible for the in vitro bioactivity of nanodiopside.
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Materials Science · Cross-listed from physics.med-ph
Fabrication, drug delivery kinetics and cell viability assay of PLGA-coated vancomycin-loaded silicate porous microspheres
N. Zirak, A. Maadani, E. Salahinejad et al. (+2 more)
Porous ceramic microspheres are a desirable substance for bone tissue reconstruction and delivery applications. This study focuses on Mg-Ca silicate microspheres encapsulated in biodegradable poly (lactic-co-glycolic acid) (PLGA) to serve as a biocompatible carrier for the controlled release of vancomycin hydrochloride. In this regard, diopside (MgCaSi2O6), bredigite (MgCa7Si4O16) and akermanite (MgCa2Si2O7) powders were synthesized by sol-gel and subsequent calcination methods. Then, porous akermanite, diopside and bredigite microspheres of 700-1000 um in diameter were fabricated by using carbon porogen, droplet extrusion and sintering, then loaded with the drug and eventually coated with PLGA. The bare microspheres showed a considerable burst release mode of the drug into a physiological medium, whereas PLGA coating of the microspheres reduced the burst release level. To investigate effective mechanisms governing in the drug release from the carriers, the contribution of burst, degradation, and
diffusion was analyzed by the sequential quadratic programming
algorithm method. It was found that the relative contribution of
diffusion to bioresorption is ranked as diopside > akermanite > bredigite, whereas PLGA coating dominates the
diffusion mechanism. The dental pulp stem
cells cytocompatibility MTT assay of the microspheres also showed that the drug loading deteriorates but PLGA coating improves the
cell biocompatibility significantly. Comparatively, the biocompatibility of the PLGA-coated microspheres was ranked as akermanite > diopside > bredigite, as a result of a compromise between the release of the constituting ions of the ceramic carriers and vancomycin molecules. It was eventually concluded that PLGA-coated Mg-Ca silicate microspheres are promising candidates for drug-delivery bone tissue engineering and dental bone grafting applications.
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All authors N. Zirak, A. Maadani, E. Salahinejad, N. Abbasnezhad, M. Shirinbayan
Superconductivity
Altermagnetism Induced Bogoliubov Fermi Surfaces Form Topological Superconductivity
Bo Fu, Chang-An Li and Björn Trauzettel
We propose a novel type of topological superconductivity based on Bogoliubov
Fermi surfaces (BFSs) in an altermagnetic topological
insulator proximitized by an s-wave
superconductor. The 3D altermagnetic topological
insulator is characterized by zero-energy surface states in bulk nodal-ring phases and anisotropically shifted surface Dirac cones in topological insulating phases. The altermagnetic order in combination with superconductivity gives rise to highly anisotropic superconducting gaps with
crystal-facet-dependent BFSs at the physical boundaries. These particular BFSs provide distinct platforms to realize topological superconductivity. We propose a quasi-1D nanowire in which the anisotropic BFSs experience topological phase transitions due to
quantum confinement leading to Majorana zero modes (MZMs) at its ends. We further consider
vortex phase transitions in the superconducting altermagnetic topological
insulators. Remarkably, we find that the altermagnetic order allows us to transit between two distinct type of MZMs, one type is located at the
vortex line, while the other type is located at the physical boundaries. Our work paves a new avenue utilizing altermagnetism-induced BFSs to engineer topological superconductivity through
crystal anisotropy and
quantum confinement.
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Soft Condensed Matter
Stress analysis of dilute particle suspensions in non-Newtonian fluids with efficient evaluation in the weakly non-Newtonian limit
Arjun Sharma and Donald L. Koch
We present a semi-analytical framework to compute the suspension stress in dilute particle-laden non-Newtonian fluids, separating Newtonian and non-Newtonian contributions. The ensemble-averaged stress includes both the particle-induced non-Newtonian stress (PINNS) and an interaction stresslet arising from surface tractions due to the non-Newtonian stress and its induced Newtonian flow. Using a generalized reciprocal
theorem, we express this interaction stresslet entirely in terms of the non-Newtonian stress, for a general constitutive model. For weakly non-Newtonian fluids, a regular perturbation expansion combined with the method of characteristics yields all leading-order stress contributions from the Newtonian velocity field alone, avoiding the need to solve coupled partial differential equations. This generalizes the method of Koch et al. (Phys. Rev. Fluids 1, 013301 (2016)) beyond polymeric fluids to any weakly non-Newtonian medium driven by velocity and its gradients. We apply the method to two systems: (i) spheres suspended in a fluid of smaller spheroids, where the interaction stress becomes negative for sufficiently anisotropic shapes due to orientation misalignment of the spheroids; and (ii) suspensions in weakly anisotropic nematic
liquid crystals. In the latter, assuming a uniform director field fixed by an external field, PINNS vanishes while interaction stresslets remain, either opposing or enhancing background anisotropic stress. These results demonstrate the utility of our framework in capturing first-order particle-microstructure interactions across a broad class of non-Newtonian fluids.
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Superconductivity
Superconductivity Near a Quantum Critical Point: Bounds on the Transition Temperature in the $\gamma$-Model
Ahmed Elezaby and Artem Abanov
Near a
quantum critical point (QCP) in a metal, strong
Fermion-
Fermion interactions mediated by soft collective
bosons give rise to two competing phenomena: non-
Fermi liquid behavior and superconductivity that deviates from conventional BCS and Migdal-Eliashberg theories. We consider the problem of obtaining closed-form analytical lower and upper bounds on transition temperatures for such systems. We focus mainly on a class of models known as the gamma-model, a variation of the Eliashberg theory of superconductivity where the effective interaction potential scales as V(Omega) proportional to 1/|Omega|^gamma. Building on a recent reformulation of Migdal-Eliashberg theory expressed as a classical infinite
spin chain with nonlocal interactions [1,2], and employing a linear
algebra analysis of the Hessian
matrix obtained from the free energy functional, we derive rigorous, closed-form expressions for upper and lower bounds on the superconducting transition temperature for any gamma > 0. The main result of the paper is to establish an analytical upper bound on the transition temperature in closed form. Our upper bound is significantly tighter than those currently available in the literature and demonstrates rapid convergence toward results from prior numerical studies. Also, by applying the singularity condition directly to the unbounded Hessian
matrix, our independently performed calculations confirm the lower bounds previously established in the literature [3].
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Superconductivity
Yun-Mei Li, Yongwei Huang and Kai Chang
We introduce a class of
superconductors termed "quantized quadrupole
superconductors" that support Majorana corner modes according to the bulk-corner correspondence, distinct from previous works on the second-order topological
superconductors. An intrinsic physical quantity for
superconductors, i.e., the quadrupole moment serves as the topological invariant, which is always half-quantized due to the particle-hole
symmetry. As examples, two types of mixed pairings, $d_{x^{2}-y^{2}}\pm id_{xy}$ and $d_{x^{2}-y^{2}}\pm is$, induced in the
bilayer two-dimensional electron gases with Rashba
spin-orbit coupling give the quadrupole phase. Extended discussions indicate that the nontrivial phase is robust against relative phase fluctuations in the mixed pairings and the disorders. Our schemes provide realistic platforms to implement Majorana zero modes, paving the way for studying the Majorana physics.
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Superconductivity
Taiki Matsushita, Youichi Yanase, Takeshi Mizushima et al. (+2 more)
We theoretically investigate the intrinsic (
impurity-independent)
spin Nernst effect (SNE), a
spin current generation perpendicular to temperature gradients, in
spin-triplet
superconductors. We show that, in these systems, the SNE consists of two distinct contributions: a direct quasiparticle contribution and an indirect supercurrent contribution. The quasiparticle contribution originates from the momentum space Berry
curvature generated by
spin-triplet Cooper pairs. The indirect contribution arises from a compensating supercurrent that cancels the bulk thermoelectric charge current. While this contribution vanishes when the condensate has no
spin-polarization in momentum space, it can be comparable in magnitude to the quasiparticle contribution in nonunitary
superconductors. These results demonstrate that thermoelectric
spin supercurrent must be explicitly accounted for when evaluating the SNE in nonunitary
superconductors.
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All authors Taiki Matsushita, Youichi Yanase, Takeshi Mizushima, Satoshi Fujimoto, Ilya Vekhter
Superconductivity
The Nobel Prize in physics and the contribution of Ukrainian scientists to the understanding of quantum phenomena, in particular the behavior of macroscopic systems (The 2025 Nobel Prize in Physics)
O. G. Turutanov
The Nobel Prize in Physics 2025 has been awarded to John Clarke, John Martinis, and Michel Devoret for "the discovery of macroscopic
quantum mechanical tunnelling and energy quantisation in an electric
circuit". Their achievements open up possibilities for developing the next generation of
quantum technologies, including
quantum cryptography,
quantum computers, and
quantum sensors. This article explains physical grounds of these discoveries and describes the role of earlier studies of weak superconductivity and macroscopic
quantum systems by other scientists, highlighting the contribution of researchers from the B.I. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, who obtained pioneering results in this field. The paper includes short biographies of the Nobel laureates.
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Statistical Mechanics · Cross-listed from hep-th
Entanglement of General Subregions in Time-Dependent States
Wu-zhong Guo, Song He and Tao Liu
We develop a unified framework for computing Rényi and
entanglement entropies of arbitrary spacetime intervals in time-dependent states of $(1+1)$-dimensional conformal field theories. By combining the spacetime density
matrix formalism with the replica method, we show that
entanglement entropy is well defined for both spacelike and timelike separations. Applying this framework to global quenches prepared by boundary states and to local quenches generated by operator insertions, we obtain analytic expressions for the
entanglement entropy in general spacetime configurations. The results reveal qualitative differences between spacelike and timelike intervals: the timelike
entanglement entropy is time-independent in the global quench model, depends solely on the temporal separation, and universally exhibits a constant imaginary contribution. These features are naturally explained by a generalized quasiparticle picture in which
entanglement is produced precisely when one worldline of each quasiparticle pair intersects the interval. Furthermore, we demonstrate that the linear sum rule relating time- and spacelike
entanglement persists in both global and local quenches, indicating a broader universality of spacetime
entanglement in real-time
quantum dynamics.
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Strongly Correlated Electrons
Jordan-Wigner Transformation for the Description of Strong Correlation in Fermionic Systems
Thomas M. Henderson, Guo P. Chen and Gustavo E. Scuseria
Seniority is a useful way of organizing
Hilbert space for strongly correlated systems. The exact zero-seniority wave function, doubly-occupied configuration interaction (DOCI), provides accurate results (given the right orbitals) for many strongly correlated electronic systems but has a combinatorial computational cost. In many cases, pair coupled cluster doubles provides a
polynomial-cost approximation that closely reproduces the energies of DOCI, but it breaks down in some cases and, as shown herein, it does not provide particularly good density
matrices. In this work, we demonstrate that by using the Jordan-Wigner transformation to turn the seniority zero problem back into a fermionic one, we can provide mean-field variational results of DOCI quality for the Hubbard model and a few small molecular dissociation examples, with
polynomial cost, both for the energies and for density
matrices, all while being protected from collapse. This success is rooted in the proof we provide showing that the Hartree-Fock wave function on the Jordan-Wigner–transformed
Hamiltonian transforms back to variational coupled cluster doubles in the seniority zero representation, but restricted to have determinant rather than permanent amplitude coefficients, without compromising its overall accuracy.
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