Spontaneous symmetry breaking leads to ordered phases, and hysteretic behavior often serves as a hallmark of emergent thermodynamic properties. Charge-neutral rhombohedral few-layer graphene is a strongly interacting system prone to layer antiferromagnetic (LAF) insulators, owing to its nearly flat bands with a high topological winding number. Here, in ultra-clean rhombohedral trilayer graphene devices-suspended to maximize interaction effects-we observe unexpected yet reproducible density hysteresis centered at the charge neutrality point (CNP), both at zero and finite electric fields. This hysteresis accentuates under an applied in-plane Zeeman field, but gradually weakens and eventually disappears as the temperature increases from 10 mK to 500 mK. These observations highlight the many-body nature of the LAF state, indicating a discontinuity in the chemical potential at the CNP and Zeeman field driven noncollinear spin canting. Our findings broaden the understanding of correlated phenomena in rhombohedral graphene and demonstrate both electric and magnetic control over antiferromagnetic order.

Unlike 2D frameworks where conductivity is largely confined to in‐plane transport, the scu topology offers 3D conduction pathways that enhance bulk charge mobility. When integrated with redox‐active species like tetrathiafulvalene (TTF), the scu architecture promotes electron transfer across the 3D network, enabling tunable conductivity. This article presents the construction of a 3‐periodic (4,8)‐c covalent organic framework (COF), TU‐48, adopting a twofold interpenetrated scu net, achieved through the integration of a tetratopic D2h‐symmetric rectangular TTF structural motif and an octatopic D2h‐symmetric quadrangular prism linker. TU‐48 exhibits high structural order, well‐defined porosity, and redox‐responsive electrochemical behavior. The high‐connectivity 3D COF configuration ensures effective access to TTF redox centers, enabling controlled iodine oxidation and resulting in electrical conductivities of 4.3 × 10−6 S cm−1 at 298 K and 1.8 × 10−4 S cm−1 at 393 K. By demonstrating how enhanced structural connectivity in TTF‐bridged 3D covalent lattices enables improved charge‐transport properties, this research fuels innovation in sustainable energy storage solutions and electronics.

In two-dimensional transition metal dichalcogenide structures, the optical excitation of a bright exciton may be followed by the formation of a plethora of lower energy dark states. In these formation and relaxation processes between different exciton species, non-equilibrium exciton and phonon populations play a dominant role, but remain so far largely unexplored as most states are inaccessible by regular spectroscopies. Here, on the example of homobilayer 2H-MoS_2, we realize direct access to the full exciton relaxation cascade from experiment and theory. By measuring the energy- and in-plane momentum-resolved photoemission spectral function, we reveal a distinct fingerprint for dark excitons in a non-equilibrium excitonic occupation distribution. In excellent agreement with microscopic many-particle calculations, we quantify the timescales for the formation of a non-equilibrium dark excitonic occupation and its subsequent thermalization to 85 fs and 150 fs, respectively. Our results provide a previously inaccessible view of the complete exciton relaxation cascade, which is of paramount importance for the future characterization of non-equilibrium excitonic phases and the efficient design of optoelectronic devices based on two-dimensional materials.

C-H fluoroalkylation of heteroarenes and biomolecules employing inexpensive carboxylic acids based on electrophotochemical oxidation on a Fe2O3 photoanode was developed. Notably, the devised approach proved amenable to a wide range of versatile late-stage C-H fluoroalkylations of biorelevant heterocycles. Mechanistic studies supported a direct electron transfer to form a fluoroalkyl radical with a cost-efficient heterogeneous iron catalyst.

The fundamental question of how to describe ohmic resistance at the nanoscale was answered by Landauer in his seminal picture of the Landauer resistivity dipole (LRD). While this picture is theoretically well understood, experimental studies remain scarce due to the need for noninvasive local probes. Here, we use the nanometer lateral resolution of near-field photocurrent imaging to thoroughly characterize a monolayer-bilayer graphene interface. Via systematic tuning of charge carrier density and current flow, we detected charge carrier accumulation around this nearly ideal one-dimensional defect due to the formation of the LRDs. We found that, at low doping levels, the photocurrent exhibits the same polarity as the applied source-drain voltage, reflecting carrier concentration changes induced by the LRDs. This signature disappears at higher charge carrier densities in agreement with the numerical calculations performed. Photocurrent nanoscopy can thus serve as a noninvasive technique to study local dissipation at hidden interfaces.

Metal-organic frameworks have garnered interest for over 25 years in energy and electronics, yet their adoption in devices has been hindered by low electrical conductivity, largely attributed to activated transport. Our study demonstrates a significant shift, revealing metallic conductivity in Cu3(HHTP)2 thin films-240 S m-1 at room temperature and 300 S m-1 at 100 K, a departure from its presumed semiconductive nature. Achieved through robotic, AI-based layer-by-layer assembly in a self-driving laboratory, this method produces SURMOFs with minimal defects, optimized via rapid surrogate characterization techniques. Our research, supported by both electronic structure calculations and experimental verification, identifies a persistent Dirac cone in the hexagonal D6h symmetry of 2D sheets as crucial for the observed metallic behavior. Notably, even with ABAB stacking in the bulk, this Dirac cone feature maintains metallic conductivity, enhancing at lower temperatures. This breakthrough not only clarifies the conduction mechanism in Cu3(HHTP)2 but also highlights the SDL's potential in developing high-quality MOF thin films for future applications. Our findings indicate that tailoring the Dirac cone's energy could lead to a new class of highly conductive, metallic MOFs.

AB-stacked bilayer graphene has emerged as a fascinating yet simple platform for exploring macroscopic quantum phenomena of correlated electrons. Under large electric displacement fields and near low-density van-Hove singularities, it exhibits a phase with features consistent with Wigner crystallization, including negative dR/dT and nonlinear bias behavior. However, direct evidence for the emergence of an electron crystal at zero magnetic field remains elusive. Here, we explore low-frequency noise consistent with depinning and sliding of a Wigner crystal or solid. At large magnetic fields, we observe enhanced noise at low bias current and a frequency-dependent response characteristic of depinning and sliding, consistent with earlier scanning tunnelling microscopy studies confirming Wigner crystallization in the fractional quantum Hall regime. At zero magnetic field, we detect pronounced AC noise whose peak frequency increases linearly with applied DC current-indicative of collective electron motion. These transport signatures pave the way toward confirming an anomalous Hall crystal.

Metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) hold promise for advanced electronics due to their tunable structural and electronic properties. However, discrepancies in reported electrical conductivities underscore the critical role of measurement methodologies. This review explores how intrinsic charge transport mechanisms (band‐like vs hopping) and extrinsic factors (grain boundaries, contact resistance) influence performance. This review critically examines the impact of common characterization methods – including two‐probe, four‐probe, van‐der‐Pauw, thin‐film, pellet, and single‐crystal techniques – on the assessment of electronic properties in MOFs and COFs. Case studies on copper benzenehexathiol (Cu 3 BHT) and copper hexahydroxytriphenylene (Cu 3 (HHTP) 2 ) illustrate how factors such as grain boundaries and contact resistance strongly affect measured conductivities. Advanced microscopic and spectroscopic techniques (conductive atomic force microscopy, terahertz spectroscopy) provide nanoscale or dynamic insights but may not reflect macroscopic device behavior. The necessity of standardized, method‐specific reporting and careful selection of characterization strategies to bridge the gap between intrinsic material properties and real‐world electronic performance are highlighted.

Spin-orbit coupling (SOC) and electron-electron interaction can mutually influence each other and give rise to a plethora of intriguing phenomena in condensed matter systems. In pristine bilayer graphene (BLG), which has weak SOC, intrinsic Lifshitz transitions and concomitant van-Hove singularities lead to the emergence of many-body correlated phases. Layer-selective SOC can be proximity induced by adding a layer of tungsten diselenide (WSe2) on its one side. By applying an electric displacement field, the system can be tuned across a spectrum wherein electronic correlation, SOC, or a combination of both dominates. Our investigations reveal an intricate phase diagram of proximity-induced SOC-selective BLG. Not only does this phase diagram include those correlated phases reminiscent of SOC-free doped BLG, but it also hosts unique SOC-induced states allowing a compelling measurement of valley g-factor and a correlated insulator at charge neutrality, thereby showcasing the remarkable tunability of the interplay between interaction and SOC in WSe2 enriched BLG.

Electrically conductive coordination polymers (ECCPs), particularly those incorporating benzenehexathiol (BHT) ligands, are emerging as a distinctive class of electronic materials with tunable semiconducting and metallic properties. However, the exploration of novel ECCPs with low-symmetry structures and electrical anisotropy remains under development. Here, we report the on-water surface synthesis of a novel ECCP, namely Cu5BHT, which exhibits a low-symmetry structure and unique in-plane electrical anisotropy that differs from the well-known Cu3BHT phase. Utilizing imaging and diffraction techniques, we elucidate the unit cell and crystal structure of Cu5BHT, revealing an asymmetric arrangement of the kagome resembling lattice connected by two different secondary building units: square planar CuS4 and non-planar Cu2S4. Theoretical studies indicate that Cu5BHT is metallic and exhibits in-plane electrical anisotropy due to the structure arranged in interconnected well-conducting CuS4 chains and less-conducting Cu2S4 slabs oriented along single crystal direction. Single-crystal electrical measurements confirm a metallic character characterized by the increase of conductance upon cooling. Notably, the measured conductance along different crystal directions within the ab plane unambiguously reveals a significant anisotropy, with an anisotropic factor reaching ~8. This work demonstrates a novel low-symmetry ECCP and highlights its potential for achieving in-plane electrical anisotropy.

Supramolecular organization governs the structure and optoelectronic properties of organic thin films. This study shows that films based on the non‐fullerene acceptor Y6 can be precisely structured via assembly at the air‐water interface. Theoretical cross‐sectional areas, Langmuir isotherms, and Brewster angle microscopy reveal that Y6, despite its complex structure, is sufficiently amphiphilic to form well‐defined 2D layers. Mechanical annealing through repeated compression‐expansion cycles systematically improves structural uniformity, as evidenced by narrower in situ detected fluorescence spectra, while simultaneously shifting the maximum of the compressional modulus toward denser packing. Compared to spin‐cast films, Langmuir–Schaefer (LS) layers exhibit a significantly reduced Stokes shift, suggesting less reorganization after photoexcitation and thus a higher supramolecular order. Organic thin‐film transistors (OTFTs) fabricated using the LS technique achieve mobilities comparable to those of spin‐cast films, despite being substantially thinner (≤ 3 nm, determined by atomic force microscopy), thus requiring considerably less material. Notably, Y6‐LS OTFTs outperform previously reported polymer‐based LS‐OTFTs by one order of magnitude in charge carrier mobility. This work highlights the potential of interfacial assembly for thin film fabrication and underscores the advantages of mechanical annealing and in situ spectroscopy to enhance the performance of organic optoelectronic devices.

Despite significant advancements in materials design for renewable energy devices, the fundamental understanding of the underlying processes in many materials remains limited, particularly in complex, inhomogeneous systems and interfaces. In such cases, in situ studies with high spatial and energy resolution are essential for uncovering new insights into excitation, dissipation, and conversion processes. Recent progress in in situ atomic scale methods has greatly enhanced the understanding of energy materials. Here, key advances are reviewed, including in situ, environmental and ultra-fast transmission electron microscopy, scanning probe techniques, single-photon-resolved infrared spectroscopy, velocity-resolved molecular kinetics, and in situ grazing-incidence X-ray spectroscopy. These techniques enable the study of energy conversion with spatial resolution from nanometers down to individual atoms, energy resolution down to meV, and single-quantum detection. Especially they enable access to processes that involve multiple degrees of freedom, strong coupling, or spatial inhomogeneities. They have driven a qualitative leap in the fundamental understanding of energy conversion processes, opening new avenues for improving existing materials and designing novel clean and efficient energy materials in photovoltaics, friction, and surface chemistry and (photo-)electrochemistry.

Unlike two-dimensional (2D) frameworks where conductivity is typically restricted to in-plane transport, scu topology offers three-dimensional (3D) conduction pathways, enhancing bulk conductivity. When integrated with redox-active species like tetrathiafulvalene (TTF), the scu structure promotes electron transfer across the 3D network, enabling tunable conductivity. This study presents the construction of a 3-periodic [8+4]-connected COF, TU-48, adopting a 2-fold interpenetrated scu net, achieved through the integration of a tetratopic D2h-symmetric rectangular TTF structural motif and an octatopic D4h-symmetric quadrangular prism linker, displaying high structural order, well-defined porosity, and tunable electrochemical functionality. The high-connectivity 3D COF configuration optimizes access to redox centers, enabling controlled iodine oxidation and achieving an electrical conductivity of up to 1.8 × 10-4 S cm-1 at 393 K. Enhancing structural connectivity in TTF-bridged 3D covalent lattices, this research fuels innovation in sustainable energy storage solutions and electronics.

The vertical integration of multiple two-dimensional (2D) materials in heterostructures, held together by van der Waals forces, has opened unprecedented possibilities for modifying the (opto-)electronic properties of nanodevices. Graphene, with its remarkable opto-electronic properties, is an ideal candidate for such applications. Further candidates are 2D polymers, crystalline polymeric materials with customizable structure and electronic properties that can be synthesized in all mathematically possible Bravais lattices. In this study, we investigated the optoelectronic properties of a heterostructure created by pristine graphene and a rectangular 2D polyimide (2DPI) film. This imprints a new superlattice on graphene in conjunction with a direct influence on its electronic properties. Theoretical and experimental analyses reveal that interlayer charge exchange between the 2D polymer and graphene induces hole doping in the graphene layer. We have also observed that the properties of the heterostructure are dependent on the substrate used in experiments, likely due to the porous character of the 2DPI allowing direct interaction of graphene with the support. These findings highlight the unique ability to tailor functionalities in 2D polymers-based heterostructures, allowing the development of optoelectronic devices with precisely engineered properties and stimulating further exploration of the diverse phenomena accessible through tailored designs of the 2D polymers.

Two-dimensional transition metal dichalcogenides and organic semiconductors have emerged as promising material platforms for optoelectronic devices. Combining the two is predicted to yield emergent properties while retaining the advantages of each. In organic semiconductors, the optoelectronic response is typically dominated by localized Frenkel-type excitons, whereas transition metal dichalcogenides host delocalized Wannier-type excitons. However, much less is known about the characteristics of excitons at hybrid interfaces between these materials, which determine the possible energy- and charge-transfer pathways. Here we identify a hybrid exciton at one such interface using ultrafast momentum microscopy and many-body perturbation theory. We show that this hybrid exciton, formed predominantly via resonant Förster energy transfer, has both Frenkel- and Wannier-type contributions: intralayer electron-hole transitions within the organic semiconductor layer and interlayer transitions across the interface give rise to an exciton wavefunction with mixed character. This work advances our understanding of charge and energy transfer processes across 2D-organic heterostructures.

Understanding the impact of spatial heterogeneity on the behaviour of two-dimensional materials represents one of the grand challenges in applying these materials in optoelectronics and quantum information science. For transition metal dichalcogenide heterostructures in particular, direct access to heterogeneities in the dark-exciton landscape with nanometre spatial and ultrafast time resolution is highly desired but remains largely elusive. Here we report how ultrafast dark-field momentum microscopy can spatio-temporally resolve dark-exciton formation dynamics in a twisted WSe2/MoS2 heterostructure with a time resolution of 55 fs and a spatial resolution of 480 nm. This enables us to directly map spatial heterogeneity in the electronic and excitonic structure, and to correlate this with the dark-exciton formation and relaxation dynamics. The advantage of the simultaneous ultrafast nanoscale dark-field momentum microscopy and spectroscopy reported here is that it enables spatio-temporal imaging of the photoemission spectral function that carries energy- and momentum-resolved information on the single-particle band structure, many-body interactions and correlation phenomena. Dark-field momentum microscopy makes it possible to spatio-temporally and spatio-spectrally resolve the dark-exciton dynamics in a twisted transition metal dichalcogenide heterostructure.

Bernal bilayer graphene has recently been discovered to exhibit a wide range of unique ordered phases resulting from interaction-driven effects and encompassing spin and valley magnetism, correlated insulators, correlated metals, and superconductivity. This Letter reports on a novel family of correlated phases characterized by spin and valley ordering, distinct from those reported previously. These phases emerge in electron-doped bilayer graphene where the energy bands are exceptionally flat, manifested through an intriguing nonlinear current-bias behavior that occurs at the onset of the phases and is accompanied by an insulating temperature dependence. These characteristics align with the presence of charge- or spin-density-wave states that open a gap on a portion of the Fermi surface or fully gapped Wigner crystals, resulting in an exceptionally intricate phase diagram.

Two-dimensional van der Waals heterostructures (2D vdWhs) are of significant interest due to their intriguing physical properties critically defined by the constituent monolayers and their interlayer coupling. Synthetic access to 2D vdWhs based on chemically tunable monolayer organic 2D materials remains challenging. Herein, the fabrication of a novel organic–inorganic bilayer vdWh by combining π-conjugated 2D coordination polymer (2DCP, i.e., Cu 3 BHT, BHT = benzenehexathiol) with graphene is reported. Monolayer Cu 3 BHT with detectable µm 2 -scale uniformity and atomic flatness is synthesized using on-water surface chemistry. A combination of diffraction and imaging techniques enables the determination of the crystal structure of monolayer Cu 3 BHT with atomic precision. Leveraging the strong interlayer coupling, Cu 3 BHT-graphene vdWh exhibits highly efficient photoinduced interlayer charge separation with a net electron transfer efficiency of up to 34% from Cu 3 BHT to graphene, superior to those of reported bilayer 2D vdWhs and molecular-graphene vdWhs. This study unveils the potential for developing novel 2DCP-based vdWhs with intriguing physical properties.

Controlling the bandstructure of Dirac materials is of wide interest in current research but has remained an outstanding challenge for systems such as monolayer graphene. In contrast, Bernal bilayer graphene (BLG) offers a highly flexible platform for tuning the bandstructure, featuring two distinct regimes. In one regime, which is well established and widely used, a tunable bandgap is induced by a large enough transverse displacement field. Another is a gapless metallic band occurring near charge neutrality and at not too strong fields, featuring rich 'fine structure' consisting of four linearly-dispersing Dirac cones with opposite chiralities in each valley and van Hove singularities. Even though BLG was extensively studied experimentally in the last two decades, the evidence of this exotic bandstructure is still elusive, likely due to insufficient energy resolution. Here, rather than probing the bandstructure by direct spectroscopy, we use Landau levels as markers of the energy dispersion and carefully analyze the Landau level spectrum in a regime where the cyclotron orbits of electrons or holes in momentum space are small enough to resolve the distinct mini Dirac cones. We identify the presence of four distinct Dirac cones and map out complex topological transitions induced by electric displacement field. These findings introduce a valuable addition to the toolkit for graphene electronics.