Abstract The investigation of superconducting and magnetic properties in alkali-metal-intercalated aromatic hydrocarbon compounds has been an active frontier in condensed matter physics. Herein, potassium- and rubidium-intercalated 1,4-di(4-pyridyl)benzene molecular crystals were successfully synthesized via a high-vacuum annealing technique. Magnetic measurements reveal that both intercalated crystals exhibit typical Curie paramagnetic behavior in the temperature range of 1.8–300 K. Combined experimental measurements and theoretical calculations confirm that the two synthesized compounds are paramagnetic semiconductors. The magnetic moment of approximately 0.30 μ B per molecule is attributed to the transfer of valence electrons from alkali metals to the π -molecular orbital of 1,4-di(4-pyridyl)benzene. Further theoretical calculations predict that the cesium-intercalated system exhibits characteristics of a paramagnetic semiconductor, whereas the sodium-intercalated system demonstrates a non-magnetic metallic state. This study provides new experimental and theoretical insights for understanding the electronic structure and magnetic properties of aromatic intercalation compounds, and reveals the critical role of intercalant selection in regulating their physical properties.

Hopf terms are topological theta terms that are associated with a host of interesting physics, including anyons, statistical transmutation, chiral edge states, and the spin quantum Hall effect. Here, we show that Hopf terms can appear in two-dimensional metals without spin-orbit coupling in the vicinity of spin-ordered phases. In their vicinity, their spinlike order parameters have a finite amplitude, but fluctuating orientation. When both a magnetic and a spin loop-current order parameter fluctuate in the system, we show that the phase is governed by the Hopf term and realizes a Hopf symmetry protected topological phase. This phase is protected by the unbroken SU ( 2 ) spin rotation symmetry, is gapped in the bulk, has chiral gapless edge states, and its spin-Hall conductance is quantized. Lattice models that realize this phase are introduced. In addition, we provide an elementary proof that the θ angle of the Hopf term must be quantized to multiples of π in nonrelativistic systems, thereby precluding anyonic skyrmions in condensed matter systems.

Rare-earth high-entropy oxides (RE-HEOs) represent a distinct class of entropy-stabilized ceramics in which multiple lanthanide cations occupy a common crystallographic sublattice, generating strong chemical disorder, lattice distortion, and complex defect landscapes. Unlike transition-metal-based high-entropy oxides, RE-HEOs are governed by localized 4f electronic states, weak crystal-field coupling, and variable redox chemistry, leading to emergent structural, electronic, magnetic, and optical phenomena that challenge conventional solid-state descriptions. This review provides a physics-oriented analysis of RE-HEOs, focusing on the thermodynamic foundations of configurational entropy stabilization, the interplay between enthalpy, entropy, and kinetic trapping, and the consequences of severe chemical disorder for crystal structure and phase stability. We review how lattice distortion, oxygen vacancy disorder, and cation randomness modify phonon spectra, ionic transport pathways, and electronic structures, with particular emphasis on the role of localized 4f states, defect-induced in-gap levels, and disorder-broadened excitation spectra. Spectroscopic manifestations of disorder including crystal-field relaxation, line broadening, lifetime modification, and energy transfer processes are discussed within a unified framework linking local symmetry breaking to macroscopic response. We further discuss the optoelectronic properties of RE-HEOs, including photoluminescence from intra-4f transitions, upconversion mechanisms, and disorder-induced modifications of radiative lifetimes and quantum efficiency. The application landscape spans both energy conversion (electrocatalysis, solid oxide fuel cells, thermal barrier coatings) and optoelectronic technologies (phosphors, scintillators, optical thermometry, and anti-counterfeiting). Likewise, we assess theoretical and computational approaches, including density functional theory with strong correlation corrections, statistical thermodynamics, and emerging machine-learning models, highlighting their ability and current limitations in capturing disorder-driven physics in multi-component oxides. Finally, we identify open questions central to condensed-matter physics, including the nature of entropy-stabilized metastability, the limits of band theoretical descriptions in highly disordered 4f systems, and the role of configurational entropy in tuning electron-phonon and defect interactions. By consolidating experimental and theoretical insights, this review establishes RE-HEOs as a platform for exploring disorder-dominated solid-state physics beyond conventional crystalline oxides.

Dirac-like band crossings are paradigms in condensed-matter systems to emulate high-energy physics phenomena. They are associated with two aspects: gap and tilting. The ability to design a sign-changing gap gives rise to band topology, whereas the tilting of band crossings, which is a gateway for large gravitylike effects remains uncharted. In this work, we introduce an experimental platform to realize tilted Dirac-like microwave cone in large-scale superconducting circuit lattices. The direction and magnitude of the tilt can be controlled by engineering the axially preferred second-neighbor coupling. We demonstrate three lattices with 731-site L C resonator featuring tilt values of up to 59% of relative difference in the opposite-direction group velocities. This is obtained by reconstructing the density of states (DOS) of measured microwave resonance frequencies. Harnessing the tilt of Dirac-like band crossings lays the foundation for weaving the fabric of an emergent solid-state spacetime.

Recent theoretical analyses show that spin current can be induced by the baryon chemical potential gradient ∇ μ B which becomes sizable in the fireballs created in heavy-ion collisions (HIC) at a beam energy of O ( 10 ) GeV. This spin transport phenomenon can be considered as the cousin effect of the spin-Hall effect (SHE) in condensed matter systems with ∇ μ B playing the role of the analogous electric field. In this letter, we study this important mechanism, which we call “baryonic SHE” or ∇ μ B -induced polarization ( ∇ μ B -IP), for differential spin polarization generation that has not been systematically explored before. We predict the signature of the baryonic SHE in HIC using a ( 3 + 1 ) D viscous hydrodynamic model MUSIC with a multiphase transport initial condition. We propose to use the second Fourier coefficients of the net spin polarization of Λ hyperon as sensitive probes for the baryonic SHE. Those baryonic SHE observables show a qualitative difference in sign and beam energy dependence for the situations with and without the baryonic SHE. Future experimental observation of these distinct qualitative features would provide strong evidence for the existence of this “baryonic SHE” in the hot and dense quantum chromodynamics matter.

Abstract The non-trivial magnetoresistance in anomalous Hall systems (AH-MR) plays a crucial role in understanding electron dynamics in condensed matter systems. Unlike conventional Hall resistance reflecting the cyclotron motion of electrons under magnetic fields, anomalous Hall magnetoresistance typically stems from Berry-curvature-induced anomalous velocity or electron scattering events in anomalous Hall systems. Therefore, multiple parameters—such as carrier density, electrical conductivity, and anomalous Hall conductivity—offer the capability for tailoring AH-MR associated phenomena including quantum anomalous Hall effect, colossal magnetoresistance and topological phase transition. However, the high-dimensional nature for these parameters hinders the global understanding of AH-MR and related electronic transport behavior. Here we employ machine learning algorithms to architect AH-MR phase diagrams by analyzing over 2000 000 AH-MR curves generated from a two-band model with five adjustable parameters. We found these curves can be clustered into 13 distinct AH-MR states using the mean-shift algorithm and established topological networks to describe transitions between them, offering designing transition paths to switch AH-MR states by tuning selected electronic parameters. Our experimental AH-MR results on gated Fe5GeTe2 nanoflakes—serving as a validation dataset—verify the reliability of the obtained topological relationships and landscape phase diagrams. Such machine-learning-assisted approach of high-dimensional data processing offers a powerful methodology for investigating spin-dependent transport phenomena.

Abstract Parameter-dependent quantum systems often exhibit energy degeneracy points, whose comprehensive description naturally leads to the application of methods from singularity theory. A prime example is an electronic band structure where two energy levels coincide in a point of momentum space. It may happen, and this case is the focus of our work, that three or more levels coincide at a parameter point, called multifold degeneracy. Upon a generic perturbation, such a multifold degeneracy point is dissolved into a set of Weyl points, that is, generic twofold degeneracy points. In this work, we provide an upper bound to the number of Weyl points born from the multifold degeneracy point. To compute this upper bound, we describe the geometric degeneracy variety in the space of complex matrices. We compute its multiplicity at certain singular points corresponding to a multifold degeneracy, and the multiplicity of holomorphic map germs with respect to this variety. Our work covers physics and mathematics aspects in detail and attempts to bridge the two disciplines and communities. For self-containedness, we survey examples of multifold degeneracies in quantum systems and condensed-matter physics, as well as the established tools of local algebraic geometry that we use to identify the upper bound.

Magnetic/superconducting heterostructures represent a frontier in condensed matter physics, offering pathways to realize unconventional pairing mechanisms such as topological superconductivity, spin-triplet pairing, and Majorana zero modes for fault-tolerant quantum computing. In this work, we integrate the magnetic van der Waals material MnBi2Te4 (MBT) with a superconducting NbN thin film, achieving ultralow-disorder interfaces through Ti buffer layer engineering. Temperature- and field-dependent critical currents, extracted from differential resistance spectra, reveal robust coupling between the MnBi2Te4 and the superconducting order of NbN, enabling proximity-induced superconductivity within MnBi2Te4. Notably, the proximity-induced critical currents remain invariant under in-plane field rotation, in contrast to the anisotropic response observed in pristine NbN. Moreover, the hysteretic behavior observed in the interfacial magnetoresistance curves confirms the proximity-induced spin polarization at the MBT interface, which is consistent with Andreev reflection results. These findings demonstrate a platform for fabricating high-quality heterointerfaces and enable targeted exploration of exotic quantum states.

Quantum geometry, a quantum mechanical quantity comprised of Berry curvature and quantum metric, describes the geometric structure of the electronic bands in solids. The correlation between nontrivial quantum geometry and quantum materials leads to new findings in condensed matter systems. Here we demonstrate that altermagnets, with spontaneously broken time-reversal -half-lattice-translation and parity-time symmetry, host both -odd and -even quantum geometric quantities that simultaneously manifest themselves despite the vanishing net magnetization. Consequently, giant room-temperature third-order electrical transport responses with sizable quantum geometric contributions are observed in (101)-oriented RuO2 thin films, an altermagnetic candidate; in particular, the third-order Hall effect is intimately correlated with altermagnetic order and can serve as a promising tool for detecting the Néel vector. Our work not only supports the existence of altermagnetism in 8-nm-thick RuO2 thin films, but also shows altermagnets as a versatile platform for exploring quantum geometry and constructing quantum electronic and spintronic devices.

Particulate nitrate (NO3-) over North China is commonly treated as a purely secondary product in chemical transport models (CTMs), yet persistent low bias suggests a missing source. Here, we quantified plume primary NO3- (P-NO3-, filterable + condensable) over North China by integrating a sector-specific emissions framework, oxygen-isotope constraints, and WRF-CMAQ sensitivity simulations for January and August 2019. We compiled a China-specific source-profile database for filterable P-NO3- and constructed a comprehensive condensable particulate matter (CPM) inventory across 9 anthropogenic sectors. The plume P-NO3- emissions were dominated by the condensable fraction (91.5%) and industrial and power sources (92.5%). Adding CPM in CMAQ increased near-surface pNO3- by 0.98 ± 0.48 μg m-3 (10.1 ± 4.8%) in the summer and 0.99 ± 0.45 μg m-3 (4.6 ± 1.7%) in the winter, improving model performance with the response primarily expressed as enhanced emissions rather than aerosol chemistry. Similarly, a Bayesian δ18O model using a low-δ18O plume end member (20.2 ± 7.8‰) yields plume P-NO3- contributions of 13.1 ± 4.0% (summer) and 4.5 ± 2.0% (winter) and showed that omitting this end member systematically overestimated NO3- to the ·OH+NO2 pathway. These findings highlighted CPM-driven plume P-NO3- as a missing source that should be explicitly represented in inventories, CTMs, and NO3- mitigation strategies.

Dimensionality is a fundamental concept in physics, which plays a hidden but crucial role in various domains, including condensed matter physics, relativity and string theory, statistical physics, etc. In quantum physics, reducing dimensionality usually enhances fluctuations and leads to novel properties. Owing to these effects, quantum simulators in which dimensionality can be controlled have emerged as a new area of interest. However, such a platform has only been studied in specific regimes and a universal phase diagram is lacking. Here, we produce an interacting atomic quantum simulator with continuous tunability of anisotropy and temperature, and probe the universal phase diagram of dimensional crossover. At low temperatures, we identify the regimes from quantum three to zero dimensions. By increasing temperature, we observe the non-trivial emergence of a thermal regime situated between the quantum zero and integer dimensions. We show that the quantum-to-thermal transition falls into four different universality classes depending on the dimensionality. Surprisingly, we also detect a fifth type where the high-dimensional quantum system can reach the thermal phase by crossing a low-dimensional quantum regime. Our results provide a crucial foundation for understanding the projective condensed matter structures in unconventional dimensions.

Purpose . To experimentally investigate the velocity and acceleration of water droplets rising in a volume of magnetic fluid under the influence of a non-uniform magnetic field generated by a combined magnet system, which includes a ring permanent magnet placed on top of a solenoid. Methods . The experiments were conducted using a setup developed by the authors. Data collection was carried out employing standard measuring equipment. The magnetic field strength was recorded using a TPU-01 teslameter equipped with a Hall probe, which ensures high measurement accuracy. The magnetic field topology was numerically simulated using the FEMM finite element package integrated into the interactive MathLab environment. This software platform was utilized for the calculation, subsequent processing, and visualization of the magnetic field distribution generated by the combined magnet system. Image processing of the moving non-magnetic inclusions was performed using specialized software developed by the authors in the NI LabVIEW environment. The theoretical interpretation of the experimental data was based on the principles of condensed matter physics. Results . During the experiments, the dependences of the coordinate, velocity, and acceleration of disperse systems based on magnetic fluid and water on the parameters of the non-uniform magnetic field generated by the combined magnet system were obtained. Computer simulation in FEMM made it possible to evaluate the field topology affecting water droplets in the bulk of the magnetic fluid and to compare the calculated data with experimental results. It was found that the experimental and theoretical results are in good agreement. Conclusion. The obtained results demonstrate the fundamental possibility of controlling the dynamics of magnetic fluid media using the non-uniform magnetic field generated by the combined magnet system. This paves the way for the development of adjustable dispensers and systems for generating active droplets.

Abstract The concept of hybrid quasiparticles has emerged as a cornerstone of modern condensed matter physics, offering powerful means to control material properties and engineer new functionalities. Among these, the magnon polarons (MPs), a mixed state arising from the strong coupling between magnons (spin wave excitation) and phonons (lattice vibration), have recently garnered significant attention. This review article comprehensively investigates recent advancements in the field of MPs. We begin by elucidating the fundamental magnetoelastic coupling mechanisms that underlie the formation of MPs. A detailed account of the primary experimental techniques, including inelastic neutron scattering and light scattering, are provided, highlighting their unique roles in probing the spectral and spatial properties of MPs. Furthermore, we explore the profound implications of the formation of MPs on spin and heat transport phenomena, such as the spin pumping, spin Seebeck effect, and spin Peltier effect. We then present a panorama of material systems where MPs have been experimentally observed, ranging from rare-earth iron garnets to antiferromagnets, multiferroic materials, and van der Waals magnets. Finally, we discuss emerging devices, applications and future research directions, underscoring the potential of MPs as integral components in next-generation spintronic and quantum information devices.

Topological quasiparticle excited states, magnetotransport, spin Hall effect, and superconductivity in solid-state materials have consistently been the four key issues in condensed matter physics. In this work, we theoretically demonstrate that monolayer provides an effective platform to explore these intertwined phenomena through its unique electronic topology. First-principles calculations reveal a type-II Dirac point near the Fermi level of the electronic band structure of monolayer , which is split into two pairs of Weyl points with topological charges of in the presence of spin-orbit coupling. Robust edge states along the (100) direction confirm its topologically nontrivial nature. Remarkably, the system exhibits negative magnetoresistance below the temperature of 30 K with a significant Hall conductance and a predicted superconducting transition at 1.5 K, which are induced both by phonon softening and van Hove singularities. These theoretical findings establish the monolayer as a prototypical two-dimensional material for investigating type-II Dirac physics and the interplay of topological states, magnetotransport, andsuperconductivity.

In this study, an efficient method is presented for the analysis of the Klein-Gordon (KG) and Sine-Gordon (SG) equations with initial value problems. KG and SG equations are hyperbolic partial differential equations that possess the capability to model phenomena in both quantum and classical mechanics, as well as solitons and condensed matter physics. KG equation represents a relativistic wave equation while SG equation represents the d’Alembert operator with a nonlinear sine term of the dependent variable. The proposed method is based on applying the coupling of Aboodh transformation and Adomian decomposition method (ADM) to partial differential equations and this study is limited to KG and SG equations. The non-linear term is replaced by Adomian polynomials for the index n. The elements of the dependent variable are substituted within the recurrence relation by their respective Aboodh transform components corresponding to the same index. Consequently, the nonlinear problem is addressed in a direct manner, devoid of any linearization or discretization processes. Illustrations are presented to demonstrate the efficacy and veracity of the method. A comparison of the findings with the precise solution indicates that the method proved to be efficient because the results are in closed agreement with the exact solution (errors = 0 with just 5–6 terms). The study concludes that this method can be applied to a variety of linear and nonlinear partial differential equation because Aboodh Adomian Decomposition Method (AADM) provides accurate numerical solutions for linear and nonlinear problems, and can be extended to solve other problems arising in applied science.

The Qianlong Stone Classics are the largest and best-preserved ensemble of officially commissioned stone inscriptions of Confucian classics extant, yet their stele bases are currently threatened by salt efflorescence. Fluctuations in ambient temperature and humidity contribute significantly to this deterioration. Taking Stele 17 as a representative case, this study assesses the risks of surface condensation and moisture-induced salt phase transitions through integrated temperature–humidity monitoring, infrared thermography, and soluble salt analysis. The risk of condensation remains low under typical conditions, as the stele base surface temperature exceeds the dew point by at least 0.5 °C. However, risks of salt deliquescence and hydration are substantial. The stone surface contains elevated levels of soluble salts, including four highly soluble species (sodium sulfate, calcium nitrate, sodium nitrate, and sodium chloride) and one moderately soluble species (calcium sulfate). Deliquescence phase transition humidities are approximately 50.5% for calcium nitrate, 74.3% for sodium nitrate, and 75.4% for sodium chloride, while sodium sulfate exhibits a hydration phase transition near 81%. Exhibition Hall humidity fluctuates around these critical thresholds, driving repeated dissolution–crystallization and hydration–dehydration cycles that progressively erode the stone microstructure. These hygrothermal cycles exhibit pronounced seasonal patterns, with frequent air-conditioning operation in summer amplifying thermal and humidity impacts. This study elucidates an air-moisture-driven salt deterioration mechanism distinct from classical capillary rise, clarifies the persistent progression of efflorescence in transitional seasons, and provides a scientific basis for optimizing environmental control strategies.

Polar nanoregions (PNRs) are central to understanding the exceptional dielectric and piezoelectric properties of relaxor ferroelectrics and are key to advancing dielectrics for high-energy storage. However, direct real-space imaging of their formation and evolution remains a major challenge in condensed matter physics. Here, we report the real-space mappings of both PNRs and chemically ordered regions (CORs) in the prototypical relaxor Pb(Mg1/3Nb2/3)O3 and their temperature dependence using convergent-beam electron diffraction combined with four-dimensional scanning transmission electron microscopy. The results reveal that CORs, with sizes of 2–5 nm, remain static with temperature and act to suppress PNR growth. In contrast, PNRs evolve from isolated 2–5 nm regions at room temperature to interconnected structures ∼10 nm in size at low temperatures, indicative of a percolation transition. These observations support the random-field model, in which PNRs emerge from a paraelectric matrix and their growth and collective interactions are constrained by random local fields associated with CORs.

Multiferroic coupling represents a major research frontier in condensed matter physics and materials science, given its importance for both fundamental studies and device applications. While current investigations predominantly focus on magnetoelectric effects, coupling with ferroelastic order remains an outstanding challenge, especially for controlling it. Here, we report a magnetically switchable ferroelasticity effect in a 2D antiferromagnetic multiferroic lattice, where magnetization reorientation is coupled to reversible switching of ferroelastic polarization. The underlying physics originates from an intriguing spin-lattice coupling induced by zigzag antiferromagnetic exchange, which produces an anisotropic exchange field and leads to lattice distortion. This spin-lattice coupling gives rise to 120° ferroelasticity, enabling robust magnetic control of ferroelastic order. Using first-principles calculations, we further validate this effect in multiferroic monolayer FePS3. Our findings open a new pathway for the design of multiferroics with magnetically controllable properties.

Realizing topological phases in strongly correlated materials has become a major impetus in condensed matter physics. Although many compounds are now classified as topological insulators, f-electron systems provide an especially fertile platform for emergent heavy-fermion phenomena driven by the interplay of topology and many-body effects. In this study, we examine the crystalline topology of a new RAsS series (R = Y, La, Sm), revealing a structural variant from previous reports. We demonstrate that YAsS and SmAsS host hourglass fermions protected by glide symmetry. SmAsS notably exhibits a strong effective-mass enhancement, placing it alongside SmB6 and YbB12 as a material that exemplifies how the Kondo effects pin the correlated f-electron states near the Fermi energy and, consequently, renormalize the energy and mass scales of topological surface states without destroying their crystalline protection. This tunability establishes SmAsS as a bridge between weakly correlated topological materials and Kondo insulators. To capture these features, we construct a minimal model incorporating f-electron degrees of freedom, which reproduces the observed topological properties and predicts that the surface states survive in the correlated regime, albeit shifted in energy. Our work thus introduces a new family of correlated topological materials and forecasts the robustness of their surface states under Kondo correlations.

Superconductivity, characterized by dissipationless current flow with flux expulsion or quantization, is usually suppressed when the magnetic field or the temperature is sufficiently high. However, in rare instances, superconductivity can reappear upon increasing the temperature or magnetic field, a phenomenon known as reentrant superconductivity. It usually emerges from competing orders in strongly correlated materials. Here we demonstrate reentrant superconductivity as a function of both temperature and magnetic field, tuned by radio-frequency power in a relatively simple system: granular aluminum, which exhibits the properties of a naturally occurring Josephson junction array. At low temperatures, giant Shapiro steps emerge, exhibiting characteristics of a single Josephson junction. Coherent phase locking across the array's multiple junctions amplifies the quantized voltage, enabling tunability at radio frequencies, as observed in artificially designed Josephson arrays. We show that our system can be tuned from a coherent superconducting (stiff-phase) to an insulating (phase-fluctuating) state using radio-frequency power. We propose that radio-frequency power modulates the Josephson coupling energy, . Remarkably, at elevated temperatures, the screening of the electron charge suppresses the charging energy, causing superconductivity to reappear. This many-body effect cannot be described within a single junction framework and involves many-body correlations. Our system can therefore be tuned to observe both the single-junction regime and many-body correlation effects, serving as a quantum simulator for complex phenomena in condensed matter physics.