Music recommendation has been a core area of interest within the recommender systems community since its early days. With the rise of music streaming platforms, algorithmic recommendations have become central to the music industry. However, critical challenges remain concerning the design, evaluation, and societal impact of music recommender systems. This fourth edition of the Music Recommender Systems Workshop (MuRS) centers on the growing influence of generative content on music recommendation. The rapid influx of AI-generated music transforms the streaming ecosystem, raising critical questions about discoverability, authenticity, and the curational role of recommender systems. The challenges and opportunities associated with AI-generated content extend beyond music and recommender systems, demanding transparent, fair, and accountable recommendation frameworks that reflect the interests of the diverse set of stakeholders.

We investigate Higgs criticality in candidate U(1) Dirac spin liquids across a family of depleted triangular lattices: the triangular, kagome, and maple-leaf geometries. For each, we identify the symmetry-allowed spinon-pairing channel connecting the U(1) state to a proximate \($\mathbbZ_2$\) spin liquid, deriving the corresponding quantum electrodynamics \($(\mathrmQED_3)$\)-Higgs theory. While the triangular and kagome lattices share a low-energy description with \($N_f=4$\) Dirac fermions, the maple-leaf lattice yields an analogous theory with \($N_f=12$\) and a distinct nodal structure where the Dirac cones can move along high-symmetry lines in momentum space instead of gapping out. Using a large-\($N_f,b$\) expansion, we compute critical exponents and the scaling dimensions of the symmetry-allowed Yukawa couplings. Although Higgs-field fluctuations and a large fermion flavor number strongly suppress the Yukawa coupling---pushing the maple-leaf lattice closer to stability than its counterparts---we find that the coupling remains relevant at leading order in all three cases, substantially reducing its scaling dimension on the maple-leaf lattice and asymptotically breaking Lorentz and conformal invariance. Ultimately, our results provide a unified framework demonstrating how the interplay between fermion flavor count and nodal geometry dictates the fate of the \($\mathrmQED_3$\)-Higgs transition.

ABSTRACT Transverse thermoelectrics (TEs), enabling interconversion between orthogonal heat and electric currents, offers unique advantages in device geometry and design flexibility. Yet, achieving large transverse TE signals at room temperature remains challenging. Here, we establish a cooperative framework in which the goniopolar effect and the anomalous Nernst effect jointly enhance the transverse TE response in kagome magnets. We demonstrate that kagome lattice-derived electronic structures intrinsically yield axis-dependent polar Seebeck coefficients arising from flat bands and van Hove singularities (VHSs), while broken time-reversal symmetry induces topological band splitting that generates large net Berry curvature within the same energy window. Combining transport measurements, DFT calculations and real-space thermal imaging, we demonstrate a room-temperature record cooperative transverse TE signal of 15.6 µV/K in the kagome ferromagnet MgMn6Sn6 among metallic systems. Our findings establish a cooperative framework linking the anomalous Nernst and goniopolar effects and provide a widely applicable design strategy for achieving large transverse TE response in kagome magnets.

Exfoliation and cleavage create two-dimensional (2D) materials and surfaces with physical and chemical properties distinct from their bulk parents. The rising class of non-van der Waals (non-vdW) 2D materials derived from non-layered crystals provides a fascinating platform, expanding the landscape of low-dimensional materials. Current computational models, however, provide limited guidance: existing descriptors are largely tailored to vdW layered systems. Here, we introduce a general framework predicting crystal cleavage and exfoliable 2D subunits directly from bulk structures. At its core is a universal eXfoliation and Cleavage Potential (XCP) enabling large-scale screening of diverse materials at negligible computational cost. Applying this approach, we obtain 44,030 cleavable surfaces and candidate non-vdW 2D materials from which we investigate -- according to our criteria -- 2531 likely exfoliable ones using high-throughput density functional theory. A large fraction of these candidates is found to be dynamically and thermodynamically stable, while showing negligible overlap with existing 2D materials databases. Our study thus opens a systematic route to explore and design 2D materials with high chemical and structural diversity.

Living materials such as membranes, cytoskeletal assemblies, cell collectives, and tissues can often be described as active solids---materials that are energized from within, with elastic response about a well-defined reference configuration. These materials often live in complex and curved manifolds, yet most descriptions of active solids are flat. Here, we explore the interplay between curvature and nonreciprocal elasticity via a covariant effective theory on curved manifolds in combination with numerical simulations. We find that curvature spatially patterns activity, gaps the spectrum, modifies exceptional points, and introduces non-Hermitian defect modes. Together, these results establish a foundation for hydrodynamic and rheological models on curved manifolds, with direct implications for living matter and active metamaterials.

Programmable quantum simulators based on neutral atom arrays today offer powerful platforms for studying strongly correlated phases of quantum matter. Here, we employ the projective symmetry group framework to describe the symmetry fractionalization patterns in a topologically ordered \\($\$\)\\\backslashmathbb\Z\\\\_\2\\\($\$\)quantum spin liquid (QSL) synthesized in such a Rydberg array on the ruby lattice. By systematically comparing the static structure factors of all possible mean-field Ansätze against density-matrix renormalization group calculations, we identify a promising candidate for the precise \\($\$\)\\\backslashmathbb\Z\\\\_\2\\\($\$\)QSL realized microscopically. We also present detailed analyses of the dynamical structure factors as a reference for future experiments and showcase how these spin correlations can differentiate between varied QSL Ansätze.

The bismuth-rich subiodides Bi[IrBi6I12], Ag3[IrBi6I12], and BixCu3–3x[IrBi6I12] were synthesized by high-temperature reactions in sealed silica ampules and characterized by powder and single-crystal X-ray diffraction, differential scanning calorimetry, energy-dispersive X-ray spectroscopy, and density functional theory (DFT) calculations. All three compounds contain cuboctahedral [IrBi6I12]3− cluster anions composed of an iridium-centered bismuth octahedron with iodide-bridged edges, but differ markedly in the occupation of the octahedral voids of the underlying rock-salt-related packing. In Bi[IrBi6I12], the clusters are linked by Bi3+ cations into infinite chains. Ag3[IrBi6I12] adopts a rock-salt-related superstructure with a high degree of occupation of octahedral voids by Ag+ and thus represents the most densely interconnected member of this cluster family known so far. At room temperature, the silver substructure is strongly disordered and gives rise to an ionic conductivity of 1.05 × 10−4 S cm−1, whereas at 100 K a commensurately modulated fivefold superstructure reveals long-range silver ordering. Attempts to prepare the corresponding copper compound “Cu3[IrBi6I12]” were unsuccessful; instead, a phase with a homogeneity range, BixCu3–3x[IrBi6I12] with x ≥ 0.5, was obtained, in which Bi3+ is replaced by Cu+ distributed over trigonal-planar and tetrahedral sites in and around the corresponding octahedral voids. Electron-counting considerations and DFT-based bonding analyses consistently support an electron-precise 18-electron configuration for iridium in [IrBi6I12]3−. DFT calculations identify Bi[IrBi6I12] and Ag3[IrBi6I12] as narrow-gap semiconductors.

\($\mathrmTaSb_2$\), a member of the \($\mathrmTmPn_2$\) family of materials, hosts the very rare dual topological phase---weak topological insulating state and topological crystalline insulating state along different crystallographic orientations. So far, studies on the electronic structure of \($\mathrmTmPn_2$\) compounds have focused on their overall electronic structure and the bulk open-orbit Fermi surfaces. Using angle-resolved photoemission spectroscopy, density functional theory calculations, and transport measurements, we distinguish the intertwined bulk and surface states on the weakly topological \($(20\overline1)$\) plane of \($\mathrmTaSb_2$\). We identify multiple electron- and holelike bulk bands, yielding a near-perfect carrier compensation. Crucially, we observe open-orbit FSs near \($\overlineM$\) and parallel to \($\overline\mathrm\ensuremath\Gamma\ensuremath-\overlineY$\) direction that are entirely of surface origin. The surface states also exhibit band crossing at \($\ensuremath\sim0.6\phantom\rule0.16em0ex\mathrmeV$\) below Fermi level at the time-reversal invariant momentum \($\overlineM$\), indicating nontrivial band topology. Consistent with this, magnetotransport measurements display weak antilocalization, establishing \($\mathrmTaSb_2$\) as a platform for spin-polarized topological transport on a weakly topological surface.

We map the complete classical phase diagram of the spin Hamiltonian describing pyrochlore rare-earth magnets with all symmetry-allowed nearest-neighbor bond-dependent anisotropic two-spin interactions. We provide a simple derivation of the organization of spins into tensor degrees of freedom describing the multipole moments of a tetrahedron, whose components correspond to irreducible representations (irreps) of the tetrahedral symmetry group \($T_d$\). By parametrizing the Hamiltonian directly in terms of the energies of the individual irreps, we perform an exhaustive search of all possible irrep degeneracies (collisions) which may host stable classical spin liquids arising at classical multicritical points. We find four one-parameter families of models along which three phases are degenerate, all four of which merge at the Heisenberg antiferromagnetic point and its dual, and we give a complete three-dimensional picture of the phase diagram showing all of the phases and their intersections. The appearance of two copies of a single irrep implies an extra degenerate locus which pierces the phase boundaries at special points, yielding two additional isolated triple points. We demonstrate that one-parameter families of Hamiltonians are characterized by a topological invariant describing how the ground-state spin configuration winds when adiabatically transported around this degenerate locus, analogous to a diabolical locus in quantum field theory. We provide a comprehensive catalog of all flat-band degeneracies in the phase diagram and discuss the mechanisms that may allow for or impede the realization of a variety of classical spin liquids described by tensor gauge fields exhibiting nodal line singularities and concomitant multifold pinch points. Last, we provide a list of all cases where three irreps are degenerate above the ground state, which may lead to interesting features in the spin wave spectrum within each ordered phase.

ABSTRACT Misfit layer compounds (MLCs) are a versatile platform for exploring the electronic phase diagram of two-dimensional (2D) materials beyond the limits of conventional gating techniques. This work demonstrates the precise tunability of electron doping in \\($\rm NbSe\_2\$\) monolayers through chemical alloying within the rocksalt layer of \\($(\textLa\_x\textPb\_1-x\textSe)\_1.14(\textNbSe\_2)\_2\$\) heterostructures. By combining first-principles density functional theory (DFT) calculations with angle-resolved photoemission spectroscopy (ARPES), we prove that the rocksalt unit acts as a universal electron donor. We show that varying the La/Pb ratio results in a rigid Fermi level shift, still preserving the \\($\rm NbSe\_2\$\) electronic structure. Crucially, photon-energy-dependent ARPES confirms that the \\($\rm NbSe\_2\$\) layers nearly maintain their intrinsic 2D character and orbital identity within the three-dimensional misfit. This study establishes MLCs as a reliable platform for engineering emergent states in 2D transition metal dichalcogenides through precise stoichiometric control.

Nanoscrolls, radial superlattices formed by rolling up a nanomembrane, exhibit distinct electronic and magneto-transport properties compared to their flat counterparts. In this study, we theoretically demonstrate that the conductance can be precisely enhanced N times by rolling up graphene into an N-turn nanoscroll and applying a longitudinal magnetic field. This tunable positive magnetoconductance, which can persist even in non-ideal nanoscrolls, stems from the topological winding number of a carbon nanoscroll that is activated by the magnetic flux. Its maximum value increases solely with the scroll winding number (the number of turns). By integrating material geometry and topology, our work opens the door to artificially creating, customizing, and designing topological materials in rolled-up graphene-like systems.

Recommendation and personalization research is no longer confined to computer science. Relevant questions are actively explored across disciplines including information systems, communication science, management, cognitive science, psychology, education, media studies, marketing, and the social sciences, often grounded in distinct theories, methods, and evaluation traditions. “Beyond Algorithms: A Workshop on the Interdisciplinarity of Recommender Systems” (BEYOND 2026) aims to create a dedicated space at ACM RecSys 2026 to connect these perspectives. The workshop highlights how insights from adjacent fields can complement, extend, and sometimes challenge computing-centric approaches. It explicitly welcomes contributions studying recommendation, personalization, and related phenomena outside core computing venues, as well as integrative work that bridges computational and non-computational approaches. Through presentations and interactive discussions, we aim to surface diverse theoretical frameworks, methodological traditions, and evaluation paradigms. Our goal is to foster dialogue across disciplinary boundaries, make disciplinary assumptions explicit, and identify shared research challenges and opportunities for collaboration. By strengthening ties between the RecSys community and neighboring research traditions, BEYOND 2026 seeks to broaden participation and visibility for interdisciplinary research and to position RecSys as a hub for both technical innovation and cross-disciplinary exchange.

Superconducting diodes that support nonreciprocal supercurrent flow in principle constitute attractive, nondissipative, circuit elements for superconducting electronics. But their realization faces fundamental challenges, as conventional Josephson tunnel junctions are inherently reciprocal. The so far existing approaches to break the reciprocity typically involve magnetism or spin-orbit coupling, which often increase the device complexity and limit the reproducibility. Here, we demonstrate an alternative dynamical route to supercurrent nonreciprocity based on parametric driving. By applying a frequency-modulated supercurrent amplitude, we show that effective higher-order, nonharmonic terms are generated in the current-phase relation. Leveraging strong mathematical similarities with the Kapitza pendulum, we show that these terms dynamically break the reciprocity. This establishes the concept of a Kapitza supercurrent diode and demonstrates that nonreciprocal superconducting transport can be engineered by a nonequilibrium driving the conventional Josephson tunnel junctions. We propose two implementations of such a Kapitza supercurrent diode---via gate-controlled superconducting interferometers or flux-driven double-loop SQUIDs---to achieve nonreciprocal supercurrent transport within experimentally accessible frequencies \($\ensuremath\omega/2\ensuremath\pi\ensuremath\sim1$\) to 10 GHz.

Superlattice engineering in van der Waals (vdW) heterostructures (e.g., by moiré engineering) provides a powerful platform for designing electronic bands and realizing correlated and topological quantum phenomena. Here, we pioneer a scheme to tailor superpotentials based on intrinsic substrate electronic orders. We show that this establishes a robust, self-aligned, and highly versatile route to band-structure control, as we demonstrate in graphene by engineering two distinct, nearly commensurate superlattices using the charge density waves (CDWs) of 1T-NbSe2. In these superlattices, the graphene's Dirac cones are folded either to the \\($\Gamma\$\)-point or to the K-points of the mini-Brillouin zone (mBZ). Using scanning tunneling microscopy, we observe that the \\($\Gamma\$\)-folded system preserves \\($C\_3\$\) symmetry, while the K-folded system exhibits symmetry breaking. Combining density functional theory with an interlayer interaction model, we reveal that this difference is not electronically driven but originates from a structural instability. Our work establishes superlattice engineering for designer quantum states and unveils a structural mechanism for controlled emergent symmetry breaking.

We investigate thermal and nonlocal electrical transport in four-terminal Josephson junctions formed by a normal region coupled to two transverse chiral superconducting leads, supporting phases characterized by Chern numbers \($\mathcalC=0,\phantom\rule0.16em0ex1$\), and 2. For \($\mathcalC=1$\), we identify the conditions under which a single chiral Majorana mode, with equal superposition of electrons and holes, produces a robust half-integer quantized thermal conductance and a zero nonlocal electrical conductance. Thermal conductance quantization occurs near a superconducting phase difference \($\ensuremath\pi$\), but only in the low-doping regime of the central region and in the intermediate- to long-junction limits. At finite Zeeman fields, the thermal response broadly follows the topology of the isolated superconducting leads for the \($C=1$\) phase while, in the \($\mathcalC=2$\) phase, the thermal conductance generally deviates from quantization, depending on the momentum-space location of the Majorana modes. Our results establish clear criteria for probing chiral Majorana modes in Josephson junctions and highlight the essential role of momentum-space structure, finite-size geometry, and sample parameters in thermal transport.

We investigate the emergence of altermagnetic (AM) phases on the square-kagome lattice. Our analysis reveals that matrix element effects due to an orthogonal sublattice weight decomposition of Fermi level eigenstates known as sublattice interference enable decoupled magnetic ordering tendencies on distinct sublattices. Depending on which sublattice undergoes a magnetic instability, we identify a \($d_xy$\)-type AM phase and a \($d_x^2\ensuremath-y^2$\)-type AM phase originating from different sublattice polarization patterns. Using the Kotliar-Ruckenstein slave boson formalism, we explore the stability of these AM phases as a function of interaction strength. Our findings demonstrate that sublattice-selective magnetic instabilities provide a versatile route to engineer the nature of AM order.

We introduce many-body caging as a novel mechanism for nonthermal behavior in quantum matter. We define many-body cages as eigenstates that, through quantum interference, become localized on a subgraph of the many-body state graph. These many-body cages can lead to the formation of flat bands in the many-body spectrum at characteristic, system-independent energies. These flat bands can realize a novel type of glassy eigenspectrum order in the absence of disorder, which we quantify by a band-overlap order parameter with an intricate, possibly fractal, distribution over the many-body state graph. We further show that these many-body cages exhibit distinctive signatures in experimentally accessible quantities, such as through a nonvanishing long-time memory of the initial condition, and many-body Rabi oscillations set by the characteristic flat-band energies. While our predictions in principle apply to any constrained quantum system, we demonstrate them here for 2D lattice gauge theories and models relevant for current experiments in Rydberg atoms. We expect that these many-body cages offer a promising route to realize nonequilibrium quantum states with novel properties.

The electronic properties of materials exhibiting giant thermopower with a thermopower that exceeds 2000 ensuremathmuV/K, such as EuCd\($_2$\)P\($_2$\), are strongly temperature dependent.

Topological superconductivity and Majorana zero modes emerge from two feasible platforms, quasi-1D nanowires and vortex-line heterostructures, when crystal anisotropy and quantum confinement act as tuning parameters.

Transition-metal doping enables the introduction of spin functionality into halide double perovskites, while simultaneously modifying optical properties. Here, we combine controlled single-crystal growth, optical characterization, comprehensive electron paramagnetic resonance (EPR) spectroscopy, and first-principles modeling to identify the microscopic nature of Fe-related centers in Fe-doped \($\mathrmCs_2\mathrmAgBiBr_6$\). Single crystals with nominal \($\mathrmF\mathrme^3+$\) concentrations up to 15% in the precursor stage were grown using a controlled-cooling method, yielding reproducible Fe incorporation up to 0.1% with respect to Bi, without secondary phases. Despite this low concentration, Fe doping introduces electronic states that influence optical absorption and photoluminescence. EPR measurements reveal an S = 5/2 \($\mathrmF\mathrme^3+$\)-related center whose anisotropy follows the cubic-to-tetragonal phase transition below 120 K. Angular-dependent EPR resolves two configurations of this nearly axial spin center, with principal axes rotated by 90ifmmode^circelsetextdegreefi and aligned with the a/b plane of the tetragonal lattice. Density-functional calculations attribute these centers to impurity-vacancy complexes, most likely \($\mathrmFe_\mathrmBi\text\ensuremath-\mathrmV_\mathrmBr$\), that stabilize in a basal configuration of the low-temperature phase. This approach resolves vacancy-coupled defect orientations, narrowing possible models to \($\mathrmF\mathrme^3+$\)-vacancy complexes and establishing them as stable, orientation-sensitive spin probes of structural symmetry in halide double perovskites, while providing a microscopic basis for tuning their magnetic and optical responses.

A study of the counter-Nagaoka problem of a single hole in an infinite-\($U$\) Hubbard model on the kagome lattice reveals a new type of polaron, a resonating-valence-bond polaron that morphs into semiclassical order as polarization is reduced.

Building on earlier reports of superconductivity in bulk PtSb, we present a systematic study of superconductivity in epitaxial PtSb(0001) thin films grown on \($\textSrF_2(111)$\). Electrical transport measurements reveal a superconducting transition at \($T_\mathrmc=1.72\phantom\rule0.16em0ex\mathrmK$\). The field-induced broadening of the transition and the temperature dependence of the upper critical fields are consistent with type-II superconductivity. We determine the upper critical fields for magnetic fields applied perpendicular and parallel to the film plane and parametrize their temperature dependence using an anisotropic Ginzburg-Landau approach. For a representative film in the intermediate thickness regime (\($d=50\phantom\rule0.16em0ex\mathrmn\mathrmm$\)), we obtain coherence lengths of \($\ensuremath\xi_ab\ensuremath\approx56\phantom\rule0.16em0ex\mathrmn\mathrmm$\) and \($\ensuremath\xi_c\ensuremath\approx14\phantom\rule0.16em0ex\mathrmn\mathrmm$\). Current-voltage characteristics show sizable critical currents, with a critical current density reaching \($J_\mathrmc\ensuremath\approx6\ifmmode\times\else\texttimes\fi10^4\phantom\rule0.16em0ex\mathrmA/\textcm^2$\) at \($0.5\phantom\rule0.16em0ex\mathrmK$\). These results establish the superconducting properties of epitaxial PtSb thin films and provide a basis for lattice-matched heterostructures within the NiAs-type materials family.

Transverse thermoelectric devices offer simplified geometries with flexible designs for next-generation cryogenic technologies. However, mechanisms on geometrical amplification of transverse thermoelectric effects remain elusive. Here we establish a general framework linking reduced dimensionality with its geometrical anisotropy to enhanced transverse thermoelectric responses. Taking quasi-one-dimensional Li0.9Mo6O17 as a model platform, we combine theoretical modeling with systematic experiments to reveal extraordinarily large Nernst and Ettingshausen signals, reaching 11,430 \($\mu$\)V/K (25\thinspaceK, 9\thinspaceT) and 0.0063thinspaceKthinspacetextperiodcenteredthinspacem/A (43.1\thinspaceK, 9\thinspaceT), respectively, together with a high power factor of 814 \($\mu$\)W cm−1 K−2 at 25thinspaceK and 9thinspaceT. Dimensional reduction amplifies the Seebeck-driven electric field and enhances the reduced mobility through anisotropic Fermi surface geometry. These effects yield the transverse thermoelectric response far exceeding those of higher-dimensional systems with even ultrahigh carrier mobilities. Our findings highlight enhanced geometrical anisotropy as a powerful principle of design for engineering high-performance transverse thermoelectric systems.

NiS2, a material long recognized for its non-collinear magnetic order and correlated insulating behavior, has until now been entirely overlooked as a potential host of topological phenomena. Bulk NiS2 is known to be a Mott or charge-transfer insulator, yet its surface exhibits anomalous finite conductivity of unclear origin. Additionally, a definitive consensus regarding its low-temperature magnetic transition remains elusive. In this work, we provide a unified explanation for both of these longstanding puzzles. First, we present a refined characterization of NiS2's magnetic phases by proposing a novel ground state based on a rigorous symmetry analysis of high-resolution neutron scattering data. Second, through high-resolution scanning tunneling microscopy and spectroscopy (STM/STS), we reveal the presence of robust edge states on both Ni- and S-terminated surfaces, which persist even under applied magnetic fields. Using ab initio calculations combined with topological analysis, we attribute these edge states to obstructed atomic charges arising from the bulk's obstructed nature. Altogether, this study not only sheds new light on the physics of NiS2, but also establishes a solid experimental and theoretical foundation for exploring the interplay between topology and electronic correlations.

A semiclassical framework models quantum quadrupoles as biaxial tensors, showing how angular-momentum-dependent geometries dictate generalized nematic phases and quadrupolar spin liquids in frustrated magnets.

Quantum spin Hall insulators, with dissipationless edge channels protected by time-reversal symmetry, are promising for low-power and quantum devices. However, experimentally realized examples with sizable nontrivial gaps remain scarce. Monolayer Si2Te2 has been theoretically predicted to host a room-temperature quantum spin Hall phase, but the absence of a bulk analog has hindered its experimental realization. Here we show that HfTe2 provides an ideal van der Waals template for the epitaxial growth of strain-free monolayer Si2Te2 while preserving its nontrivial topological phase. Scanning tunneling microscopy and spectroscopy reveal an intact (1\texttimes1) lattice and a bulk band gap of  textasciitilde 300 meV, consistent with first-principles calculations. Moreover, pronounced edge states extending textasciitilde 2.0 nm from the island boundary are observed in monolayer Si2Te2, exhibiting characteristics expected for topological edge modes. Our results establish monolayer Si2Te2 as a large-gap two-dimensional topological-insulator platform for topological phenomena and device concepts at elevated temperatures.

Here, the authors revisit the question of the logarithmic renormalization of the Fermi velocity in graphene. Using large-scale Quantum Monte Carlo simulations of lattices with up to \($2\ifmmode\times\else\texttimes\fi10^4$\) interacting electrons, they directly connect experimental data with unbiased, nonperturbative calculations starting from a microscopic Hamiltonian. Their results reveal that even random-phase approximation corrections are quantitatively insufficient at realistic interaction strengths for suspended graphene, while continuum perturbation theory misses important lattice-scale effects. Remarkably, the optical conductivity still remains constant pointing to exact cancellation of different corrections.

Traditional theories of electron transport in crystals are based on the Boltzmann equation and do not capture physics arising from quantum coherence. We introduce a transport formalism based on orbital Wigner functions, which accurately captures quantum coherent physics in multiband fermionic systems. We illustrate the power of this approach compared with traditional semiclassical transport theory by testing it numerically against microscopic simulations of one-dimensional, noninteracting, two-band systems---the simplest systems capable of exhibiting interorbital coherence. We show that orbital Wigner functions accurately capture strongly nonequilibrium features of electron dynamics that lie beyond conventional Boltzmann theory, such as the ballistic transport of a relative phase between microscopic orbitals and topological Thouless pumping of charge, both at nonzero temperature and away from the adiabatic limit. Our approach is motivated in part by modern ultracold atom experiments that can prepare and measure far-from-equilibrium charge transport and phase coherence in multiband fermionic systems, calling for correspondingly precise theories of transport. The quantitative accuracy exhibited by our approach, together with its capacity to capture nontrivial physics even at the ballistic scale, establishes orbital Wigner functions as an ideal starting point for developing a fully systematic theory of transport in crystals.

We study twisted bilayer \($\mathrmWSe_2$\) within a continuum moir'e model and apply a method for treating finite geometries directly in the continuum framework, thereby avoiding the limitations associated with purely momentum-space formulations and Wannier obstructions. By projecting a confinement potential onto bulk moir'e eigenstates, we obtain a real-space description of edge physics without lattice models. Applying this approach to nanoribbons, we demonstrate chiral edge modes consistent with bulk Chern numbers and reveal their moir'e-scale character. In the magic-angle regime, these states are strongly localized, exhibit layer-polarized counterpropagating modes, and are electrically tunable via a displacement field, enabling control of localization, hybridization, and topological transitions. Our results establish a general framework for boundary physics in topological moir'e materials.

Transport properties of strongly correlated materials have contributions from quasiparticle excitations such as electrons and holes as well as emerging collective excitations such as plasmonic soundlike modes which are sustained by interactions. It was previously shown by Pongsangangan et al. [Phys. Rev. B 106, 205127 (2022)] that the thermal excitation of the long-lived plasmons in graphene provides a substantial contribution to heat and momentum transport in the interaction-dominated regime. Detailed information on these excitations is therefore necessary for the understanding of hydrodynamic transport with quantitative precision. On the other hand, dynamics of graphene plasmons is usually studied using perturbation theory within the Dirac cone approximation, thus neglecting the effects of a finite Brillouin zone (BZ) and higher-order perturbative corrections. Both these effects can be, however, significant for strong-interacting systems including free-standing graphene, where the effective coupling constant can reach values up to \($\ensuremath\alpha=\frace^2\ensuremath\hbarv_\mathrmF=2$\). Consequently, in this paper, we study the behavior of plasmons in half-filled free-standing graphene using unbiased quantum Monte Carlo (QMC) calculations. We confirm the existence of well-defined resonance peaks for plasmons around the \($\mathrm\ensuremath\Gamma$\) point. Comparison with the random phase approximation (RPA) calculation for the honeycomb lattice shows qualitative agreement with QMC. However, RPA yields more stable plasmon modes, while QMC shows enhanced broadening due to nonperturbative interaction effects naturally included in the simulations. To account for this effect, we generalize the calculation of lattice RPA by dressing the fermionic propagator by a constant lifetime. As a result, the plasmon frequencies are shifted toward higher energies, and the spectrum is broadened, yielding better agreement with QMC. Our findings highlight the need to account for both a finite BZ and strong interaction effects when developing theories of electronic transport in free-standing graphene.

Chirality induced by rolling a two-dimensional material into a spiral geometry reshapes its electronic band structure. In this work we theoretically investigate the topological properties of carbon nanoscrolls under an axial magnetic field, focusing on structures in which chirality is encoded through shifted edge alignments. In contrast to unshifted structures, where mirror symmetry pins the Dirac cones to half a flux quantum, chiral carbon nanoscrolls lack this symmetry, and Dirac cones emerge at magnetic flux values away from half a flux quantum. We demonstrate that these Dirac cones are topologically protected by combined inversion--time-reversal symmetry and remain robust even when sublattice symmetry is broken. Furthermore, we show that the number of Dirac cones and their real-space probability distributions depend on the number of turns and the magnetic field strength. Our study elucidates the role of chirality in the band topology of nanoscroll geometries.

We have studied the magnetic properties of clinoatacamite \($\mathrmCu_2\mathrmCl(\mathrmOH)_3$\), the parent compound of the quantum spin liquid candidate herbertsmithite and a long-standing puzzle among frustrated quantum magnets. As we reveal using density-functional theory, clinoatacamite belongs to the class of distorted kagome antiferromagnets with the kagome plane being embedded into a low-symmetry crystal structure. By means of thermodynamic measurements, muon spin rotation and relaxation, as well as neutron diffraction on single crystals, we find in zero magnetic field complex behavior below \($T_\mathrmI=18.1\text \text \mathrmK$\) which unfolds in three temperature regions I--III. We propose this complexity in multicritical clinoatacamite to arise from the competition of antiferromagnetic ordering modes from the underconstrained manifold of modes, which can lead to a metamagnetic texture in zero field.