Polyester dendrimer decorated magnetic graphene quantum dots as a pH-sensitive nanocarrier for the delivery of silibinin as an anticancer drug

Spin models for energetics of polytypes in face-centered cubic metals

Tuning the density of paramagnetic spin centers (PSCs) in π-conjugated systems enables controllable magnetism, coherent spin transport, and molecular spin qubits, thereby opening new frontiers in metal-free quantum magnetism and spintronic technologies. Here, we investigate how key quantum-mechanical and structural parameters govern the balance between spin pairing and unpaired spin density in sp2-carbon-conjugated systems. A modified Hubbard-style Hamiltonian that incorporates electrostatic interactions and static disorder combined with combinatorial analysis and Monte Carlo simulations is employed to analyze how spin density can be tuned in linear polymers, two-dimensional (2D) Lieb-type monolayers, and π-stacked 2D Lieb lattices. We find that the interplay among spin-spin repulsion, spin-anion attraction, anion-anion repulsion, π-connectivity, building-block design, and pore geometry collectively determines whether systems favor spin pairing or stabilize unpaired PSCs. Our results show that 2D π-stacked systems can intrinsically suppress spin pairing, thereby enabling enhanced PSC densities relative to 2D monolayers and 1D linear polymers, consistent with experimental observations. Overall, these findings establish a series of robust design principles that can be used to tune PSC concentrations for applications ranging from isolated spin qubits to collective magnetic and spin-transport networks, thereby advancing the rational design of quantum-coherent, metal-free π-conjugated materials.

We study pattern formation within the J1-J3 - spin model on a two-dimensional square lattice in the case of incompatible (ferromagnetic) boundary conditions on the spin field. We derive the discrete-to-continuum Γ-limit at the helimagnetic/ferromagnetic transition point, which turns out to be characterized by a singularly perturbed multiwell energy functional on gradient fields. Furthermore, we study the scaling law of the discrete minimal energy. The constructions used in the upper bound include besides rather uniform or complex branching-type patterns also structures with vortices. Our results show in particular that in certain parameter regimes the formation of vortices is energetically favorable.

Synthetic antiferromagnetic (SAF) skyrmions have emerged as promising candidates for next-generation high-speed and highly integrated spintronic devices owing to their exceptional properties, such as high driving velocity, nanoscale dimensions, and the absence of the skyrmion Hall effect. In this work, we report the experimental observation of the topological Hall effect in both compensated and non-compensated SAF skyrmion systems based on the [Pt/Co/Ru]2 trilayer. The antiferromagnetic skyrmions are further demonstrated to be robust in these SAFs under zero field. Our first-principles calculations, atomistic spin model simulations, and transmission electron microscopy measurements show that the observed topological Hall Effect is related to the skyrmion structures in the Ru and Pt layers, which are induced by the magnetic proximity effect and atomic diffusion. This work examines the role of the magnetic proximity effect in the topological Hall effect of SAF skyrmions in these systems.

Thermal tensor network approach for spin-lattice relaxation in quantum magnets

Nitrogen-vacancy (NV) centers in diamond are utilized extensively as quantum sensors for imaging fields at the nanoscale. The ultrahigh sensitivity of NV magnetometers has enabled the detection and spectroscopy of individual electron spins, with potentially far-reaching applications in condensed matter physics, spintronics, and molecular biology. However, the surfaces of these diamond sensors naturally contain electron spins, which create a background signal that can be hard to differentiate from the signal of the target spins. In this study, we develop a surface modification approach that eliminates the unwanted signal of these so-called dark electron spins. Our surface passivation technique, based on coating diamond surfaces with a thin titanium oxide ( Ti O 2 ) layer, reduces the dark spin density. The observed reduction in dark spin density aligns with our findings on the electronic structure of the diamond- Ti O 2 interface. The reduction, from a typical value of 2000 μ m − 2 to a value below that set by the detection limit of our NV sensors ( 200 μ m − 2 ), results in a twofold increase in Hahn-echo coherence time of near surface NV centers. Furthermore, we derive a comprehensive spin model that connects dark spin relaxation with NV coherence, providing additional insights into the mechanisms behind the observed spin dynamics. Our findings are directly transferable to other quantum platforms, including nanoscale solid-state qubits and superconducting qubits.

Abstract Two-dimensional (2D) magnets host a wide range of exotic magnetic textures, whose low-energy excitations and finite-temperature properties are typically described by effective spin models based on Heisenberg-like Hamiltonians. A key challenge in this framework is the reliable determination, from ab initio calculations, of exchange parameters and their anisotropic components, crucial for stabilising long-range order. Among the strategies proposed for this task, the energy-mapping method, based on total-energy calculations within Density Functional Theory (DFT), is the most widely adopted, but typically requires laborious, multi-step procedures. To overcome this limitation, we introduce AMaRaNTA (Automating Magnetic paRAmeters iN a Tensorial Approach), a computational package that systematically automates the energy-mapping method, through its “four-state” formulation, to extract exchange and anisotropy parameters in 2D magnets. In its current implementation, AMaRaNTA returns the nearest-neighbour exchange tensor, complemented by scalar parameters for second- and third-nearest-neighbour exchange interactions as well as single-ion anisotropy. Together, these provide a minimal yet sufficient set of parameters to capture magnetic frustration and anisotropies, essential for stabilising several observed magnetic states in 2D materials. Applied to a representative subset of the Materials Cloud 2D Structure database, AMaRaNTA demonstrates robust and reproducible screening of magnetic interactions, with clear potential for high-throughput simulations.

Dipoles in triangular optical ladders constitute a flexible platform for the study of the interplay between geometric frustration and long-range anisotropic interactions, and in particular for the observation of the spontaneous onset of chirality. Frustration magnifies the effect of the dipolar interactions in itinerant polarized dipolar bosons. As a result, the dipole-induced transition between a chiral superfluid and a nonchiral two-component superfluid may be observed for current state-of-the-art temperatures even for the weak intersite interaction characterizing magnetic atoms in standard optical lattices. On the other hand, pinned spin- 1 / 2 dipoles, which we discuss in the context of polar molecules in two rotational states, realize frustrated dipolar XXZ spin models. By controlling the external electric field strength and orientation, these systems can explore a rich ground-state landscape including chiral and nematic phases, as well as intriguing chiral dynamics.

New technologies for the production of man-made cellulose fibers are being developed to produce fibers sustainably for various textile applications. The Ioncell® process uses an ionic liquid in which cellulose is dissolved to form a spinning solution. This spinning solution is spun into an aqueous coagulation bath using dry-jet wet spinning technology to produce Ioncell fibres. In order to develop a sustainable and economically viable process, the ionic liquid must be efficiently recycled in the process. Organic compounds resulting from degradation reactions of the cellulosic materials used for fiber production might accumulate in the ionic liquid over time and reduce its dissolution power. This study aimed to tentatively identify the main carbohydrate transformation products from aqueous ionic liquid solution. In addition to the actual coagulation bath sample, carbohydrate transformation reactions were studied using model samples. The main monomeric carbohydrate constituents of a hardwood pulp, glucose and xylose, were mixed with an ionic liquid and water and heated to 90°C for 8h to accelerate the transformation reactions. Most of the original monosaccharides were converted into other compounds, so that after the heat treatment only 11wt% of the glucose and 1.1wt% of the xylose remained. The liquid chromatography/time-of-flight mass spectrometry analyses revealed that both the spin bath sample and model samples contained mainly hydroxycarboxylic acids and carboxylic acids. The superbase of ionic liquid catalyzed the alkaline transformation reactions of carbohydrates.

We demonstrate here that a chain of bilayer graphene quantum dots (BLGQDs) can realize topological quantum matter by effectively simulating a spin-1 chain that hosts the Haldane phase within a specific range of parameters. We describe a chain of BLGQDs with two electrons per dot using an atomistic tight-binding model combined with exact diagonalization to solve the interacting few-electron problem. Coulomb interactions and valley-mixing effects are treated within a single microscopic framework, allowing us to systematically investigate spin and valley polarization transitions as functions of interaction strength and external tuning parameters. We calculate the low energy states for single and double QDs as a function of the number of electrons, identifying regimes of highly correlated multielectron states. We confirm the presence of a spin-1 ground state for two electrons. Then, we explore two coupled QDs with four electrons and extend the analysis to QD arrays. Using a mapping of the BLGQD chain to an effective bilinear-biquadratic (BLBQ) spin model, we demonstrate that BLGQD arrays can work as a quantum simulator for one-dimensional spin chains with emergent many-body topological phases.

We measured the thermal conductivity of the rare-earth orthoferrites, RFeO_{3}, where R=Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb from 3 to 300K and see an anomalous strong suppression for TmFeO_{3} over most of the temperature range. Using a Debye thermal transport model, we demonstrate that this suppression is due to resonant scattering between phonons and the Tm^{3+} 4f singlet crystal field levels. The implications of these results are discussed in the context of thermal conductivity studies in quantum magnets.

Breakdown of the thermodynamic limit in quantum spin and dimer models

Abstract Quantum phase transitions are an established setting for emergent phenomena driven by strong electronic correlations, including strange metals and unconventional superconductivity. These have been explored extensively in Kondo lattice materials tuned to an antiferromagnetic quantum critical point (QCP), but superconductivity emerging near ferromagnetic quantum criticality is not yet observed, and the conditions under which it occurs in proximity to ferromagnetism are undetermined. Here, we report a new setting for superconductivity in the ferromagnetic Kondo-lattice material Ce5CoGe2, where there is a ferromagnetic ground state at ambient pressure, which evolves to antiferromagnetism under applied pressures. The antiferromagnetic transition is suppressed to a zero-temperature QCP, which is accompanied by strange-metal behavior. Superconductivity does not occur at the QCP, but instead appears at pressures beyond the magnetic instability. These findings suggest that Ce5CoGe2 represents a distinct class of correlated materials exhibiting a unique scenario for the emergence of superconductivity, likely associated with unconventional pairing mechanisms beyond spin-fluctuations.

Understanding the interplay between nonstabilizerness and entanglement is crucial for uncovering the fundamental origins of quantum complexity. Recent studies have proposed entanglement spectral quantities, such as antiflatness of the entanglement spectrum and entanglement capacity, as effective complexity measures, establishing direct connections to stabilizer Rényi entropies. In this work, we systematically investigate quantum complexity across a diverse range of spin models, analyzing how entanglement structure and nonstabilizerness serve as distinctive signatures of quantum phases. By studying entanglement spectra and stabilizer entropy measures, we demonstrate that these quantities consistently differentiate between distinct phases of matter. Specifically, we provide a detailed analysis of spin chains including the XXZ model, the transverse-field XY model, its extension with Dzyaloshinskii-Moriya interactions, as well as the Cluster Ising and Cluster XY models. Our findings reveal that entanglement spectral properties and magic-based measures serve as intertwined, robust indicators of quantum phase transitions, highlighting their significance in characterizing quantum complexity in many-body systems.

Lignin, a crucial renewable biomass component, represents a high-value pathway for achieving efficient biomass utilization. However, its complex and stable structure hinders the development of effective lignin depolymerization catalysts. In this study, the water-soluble H3PMo12O40 was combined with [Bmim]+ to form hydrophobic [Bmim]3PMo, which was supported on ZrO2 at various weight ratios to prepare [Bmim]3PMo@ZrO2 catalysts. These catalysts demonstrate excellent activity in lignin oxidative depolymerization, selectively producing monomeric phenolics (methyl vanillate, vanillin, methyl syringate, syringaldehyde). The 40 wt % [Bmim]3PMo@ZrO2 catalyst achieves optimal performance with 88.5% lignin conversion and 12.4 wt % phenolic yield. Two-dimensional nuclear magnetic resonance heteronuclear single quantum coherence (2D HSQC NMR) analysis confirms that the catalyst effectively cleaves the critical β-O-4 linkages in lignin. Furthermore, [Bmim]3PMo@ZrO2 has excellent reusability with stable performance over five cycles. These findings establish [Bmim]3PMo@ZrO2 as a promising lignin valorization candidate, inspiring efficient catalyst design for producing high-value aromatic compounds.

Restoring thermalization in long-range quantum magnets with staggered magnetic fields

A clean interface between two Weyl semimetals features a universal, field-linear tunnel magnetoconductance of ( e 2 / h ) N ho per magnetic flux quantum, where N ho is the number of chirality-preserving topological interface Fermi arcs. In this work we show that the linearity of the magnetoconductance is robust with respect to interface disorder. The slope of the magnetoconductance changes at a characteristic field strength B arc —the field strength for which the time taken to traverse the Fermi arc due to the Lorentz force is equal to the mean inter-arc scattering time. For fields much larger than B arc , the magnetoconductance is unaffected by disorder. For fields much smaller than B arc , the slope is no longer determined by N ho but by the simple fraction N L N R / ( N L + N R ) , where N L and N R are the numbers of Weyl-node pairs in the left and right Weyl semimetal, respectively. We also consider the effect of spatially correlated disorder potentials, where we find that B arc decreases exponentially with increasing correlation length. Our results provide a possible explanation for the recently observed robustness of the negative linear magnetoresistance in grained Weyl semimetals.

Abstract Motivated by the search for unconventional orders in frustrated quantum magnets, we present a multi-method investigation into the nature of the quantum phase diagram of the spin-1/2 Heisenberg model on the maple-leaf lattice with three symmetry-inequivalent nearest-neighbor interactions. It has been argued that the parameter regime with antiferromagnetic couplings on hexagons J h and ferromagnetic couplings on triangles J t and dimer J d bonds is potentially host to a cornucopia of emergent phases with unconventional orders. Our analysis indeed identifies an extended region where any conventional dipolar magnetic order is absent. A hexagonal singlet state is found in the region around J d = J t = 0, while a dimerized hexagonal singlet order of a lattice nematic character appears proximate to the phase boundary with the c120° antiferromagnetic order. Interestingly, upon traversing the bulk of the paramagnetic (PM) region, we find a variety of distinct correlation profiles, which are qualitatively different from those of the hexagonal singlet and dimerized hexagonal singlet orders but feature no appreciable spin-nematic response, while the boundary with the ferromagnetic phase shows evidence of spin-nematic order. This PM region is thus likely host to an ensemble of nonmagnetic phases, which could putatively include quantum spin liquids. Our phase diagram is built from a complementary application of state-of-the-art implementations of the cluster mean-field and pseudo-fermion functional renormalization group approaches, together with an unconstrained Luttinger–Tisza treatment of the model providing insights from the semi-classical limit.

A fundamental question in condensed matter physicsconcerns how topological electronic states are influenced by many-body correlations, and magnetic Weyl semimetals represent an important material platform to address this problem. However, the magnetic structures realized in these materials are limited, and in particular, no clear example of an undistorted helimagnetic state has been definitively identified. Here, we report clear evidence of a harmonic helimagnetic cycloid with an incommensurate magnetic propagation vector Q in the Weyl semimetal GdAlSi via resonant elastic X-ray scattering, including rigorous polarization analysis. This cycloidal structure is consistent with the Dzyaloshinskii-Moriya interaction prescribed by the polar crystal structure of GdAlSi. Upon applying a magnetic field, the cycloid undergoes a transition to a novel multi-Q state. This field-induced, noncoplanar texture is consistent with our numerical spin model, which incorporates theDzyaloshinskii-Moriya interaction and, crucially, anisotropic exchangeinteractions. The perfectly harmonic Weyl helimagnet GdAlSi serves as a prototypical platform to study electronic correlation effects in periodically modulated Weyl semimetals.