Magnetochiral tunneling in paramagnetic Co1/3NbS2.

Electric currents have the intriguing ability to induce magnetization in nonmagnetic crystals with sufficiently low crystallographic symmetry. Some associated phenomena include the non-linear anomalous Hall effect in polar crystals and the nonreciprocal directional dichroism in chiral crystals when magnetic fields are applied. In this work, we demonstrate that the same underlying physics is also manifested in the electronic tunneling process between the surface of a nonmagnetic chiral material and a magnetized scanning probe. In the paramagnetic but chiral metallic compound Co1/3NbS2, the magnetization induced by the tunneling current is shown to become detectable by its coupling to the magnetization of the tip itself. This results in a contrast across different chiral domains, achieving atomic-scale spatial resolution of structural chirality. To support the proposed mechanism, we used first-principles theory to compute the chirality-dependent current-induced magnetization and Berry curvature in the bulk of the material. Our demonstration of this magnetochiral tunneling effect opens up an avenue for investigating atomic-scale variations in the local crystallographic symmetry and electronic structure across the structural domain boundaries of low-symmetry nonmagnetic crystals.

Detecting dipolarity of the geomagnetic field in the paleomagnetic record.

Recovering the geomagnetic field strength in the past is key to understanding deep Earth dynamics and detecting potential geodynamo regimes throughout the history of Earth. To better constrain the predictive power of the paleomagnetic record, we propose an approach based on the analysis of the dependency between geomagnetic field strength and inclination (angle made by the horizontal with the field lines). Based on the outcomes of statistical field models, we show that these two quantities should correlate for a wide range of Earth-like magnetic fields, even with enhanced secular variation, persistent nonzonal components, and severe noise contamination. Focusing on the paleomagnetic record, we show that the correlation is not significant for the Brunhes polarity chron, what we ascribe to inadequate spatiotemporal sampling. In contrast, the correlation is significant for the 1 to 130 Ma interval, whereas it only marginally succeeds prior to 130 Ma when strict filters on both paleointensities and paleodirections are applied. As we cannot detect significant variations in the strength of the correlation over the 1 to 130 Ma interval, we conclude that the Cretaceous Normal Superchron may not be associated with enhanced dipolarity of the geodynamo. The strong correlation obtained prior to 130 Ma when strict filters are applied indicates that the ancient field may not be on average so different from the present-day field. If long-term fluctuations nevertheless existed, detecting potential geodynamo regimes during the Precambrian is currently impeded by the sparsity of high-quality data passing strict filters in both paleointensities and paleodirections.

Early warning of the Indian Ocean Dipole using climate network analysis.

SignificanceThe Indian Ocean Dipole (IOD), an air-sea coupled phenomenon over the tropical Indian Ocean, has substantial impacts on the climate, ecosystems, and society. Due to the winter predictability barrier, however, a reliable prediction of the IOD has been limited to 3 or 4 mo in advance. Our work approaches this problem from a new data-driven perspective: the climate network analysis. Using this network-based method, an efficient early warning signal for the IOD event was revealed in boreal winter. Our approach can correctly predict the IOD events one calendar year in advance (from December of the previous year) with a hit rate of higher than 70%, which strongly outperforms current dynamic models.

Enhanced localized dipole of Pt-Au single-site catalyst for solar water splitting.

Solar water splitting is regarded as holding great potential for clean fuels production. However, the efficiency of charge separation/transfer of photocatalysts is still too low for industrial application. This paper describes the synthesis of a Pt-Au binary single-site loaded g-C3N4 nanosheet photocatalyst inspired by the concept of the dipole. The existent larger charge imbalance greatly enhanced the localized molecular dipoles over adjacent Pt-Au sites in contrast to the unary counterparts. The superposition of molecular dipoles then further strengthened the internal electric field and thus promoted the charge transportation dynamics. In the modeling photocatalytic hydrogen evolution, the optimal Pt-Au binary site photocatalysts (0.25% loading) showed 4.9- and 2.3-fold enhancement of performance compared with their Pt and Au single-site counterparts, respectively. In addition, the reaction barrier over the Pt-Au binary sites was lowered, promoting the hydrogen evolution process. This work offers a valuable strategy for improving photocatalytic charge transportation dynamics by constructing polynary single sites.

Deciphering the Effect of Defect Dipoles on the Polarization and Electrostrain Behavior in Perovskite Ferroelectrics.

Defect dipoles are crucial for regulating electromechanical properties in piezoelectric ceramics, but their effects on polarization and electrostrain behaviors are still unclear. Here, a reasonable theoretical model is proposed and evidenced by experiments to address a long-standing puzzle of the relationship between the internal bias field and defect dipoles. By incorporating the additional polarization induced by defect dipoles, we refine the classical theory to account for the recently reported asymmetric giant-strain behaviors. Phase-field simulation reveals the electrostrain evolution in response to defect dipole elastic distortion and additional polarization. This work not only elucidates the effect of defect dipoles on polarization and electrostrain but also advances the theoretical understanding of defects in piezoelectrics.

Vacancy-Induced Symmetry Breaking in Titanium Dioxide Boosts the Photocatalytic Hydrogen Production from Methanol Aqueous Solution.

The key to optimizing photocatalysts lies in the efficient separation and oriented migration of the photogenerated carriers. Herein, we report that breaking continuous TiO6 tetragonal (D4h) symmetry in titanium dioxide material by oxygen vacancy engineering could induce a dipole field within the bulk phase and thus facilitate the separation and transfer of photogenerated electron-hole pairs. After further loading of Cu single-atom co-catalysts, the obtained catalyst attained a hydrogen (H2) yield rate of 15.84 mmol g-1 h-1 and a remarkable apparent quantum yield of 12.67% at 385 nm from methanol aqueous solution. This catalyst also demonstrated impressive stability for at least 24 h during the photocatalytic tests. The innovative concept of producing dipole fields in semiconductors by breaking the crystal symmetry offers a new perspective for designing photocatalysts.

Engineering van der Waals Contacts by Interlayer Dipoles.

Tuning the interfacial Schottky barrier with van der Waals (vdW) contacts is an important solution for two-dimensional (2D) electronics. Here we report that the interlayer dipoles of 2D vdW superlattices (vdWSLs) can be used to engineer vdW contacts to 2D semiconductors. A bipolar WSe2 with Ba6Ta11S28 (BTS) vdW contact was employed to exhibit this strategy. Strong interlayer dipoles can be formed due to charge transfer between the Ba3TaS5 and TaS2 layers. Mechanical exfoliation breaks the superlattice and produces two distinguished surfaces with TaS2 and Ba3TaS5 terminations. The surfaces thus have opposite surface dipoles and consequently different work functions. Therefore, all the devices fall into two categories in accordance with the rectifying direction, which were verified by electrical measurements and scanning photocurrent microscopy. The growing vdWSL family along with the addition surface dipoles enables prospective vdW contact designs and have practical application in nanoelectronics and nano optoelectronics.

Effective Manipulation of a Colossal Second-Order Transverse Response in an Electric-Field-Tunable Graphene Moiré System.

The second-order nonlinear transport illuminates a frequency-doubling response emerging in quantum materials with a broken inversion symmetry. The two principal driving mechanisms, the Berry curvature dipole and the skew scattering, reflect various information including ground-state symmetries, band dispersions, and topology of electronic wave functions. However, effective manipulation of them in a single system has been lacking, hindering the pursuit of strong responses. Here, we report on the effective manipulation of the two mechanisms in a single graphene moiré superlattice, AB-BA stacked twisted double bilayer graphene. Most saliently, by virtue of the high tunability of moiré band structures and scattering rates, a record-high second-order transverse conductivity ∼ 510 µm S V-1 is observed, which is orders of magnitude higher than any reported values in the literature. Our findings establish the potential of electrically tunable graphene moiré systems for nonlinear transport manipulations and applications.

Vertical Dipole Dominates Charge Carrier Lifetime in Monolayer Janus MoSSe.

Two-dimensional semiconductor materials with vertical dipoles are promising photocatalysts as vertical dipoles not only promote the electron-hole separation but also enhance the carrier redox ability. However, the influence of vertical dipoles on carrier recombination in such materials, especially the competing relationship between vertical dipoles and band gaps, is not yet clear. Herein, first-principles calculations and nonadiabatic molecular dynamics simulations were combined to clarify the influence of band gap and vertical dipole on the carrier lifetime in Janus MoSSe monolayer. By comparing with the results of MoS2 and MoSe2 as well as exploring the carrier lifetime of MoSSe under strain regulation, it has been demonstrated that the vertical dipole, rather than the band gap, is the dominant factor affecting the carrier lifetime. Strikingly, a linear relationship between the carrier lifetime and vertical dipole is revealed. These findings have important implications for the design of high-performance photocatalysts and optoelectronic devices.

Single-Molecule Orientation Imaging Reveals the Nano-Architecture of Amyloid Fibrils Undergoing Growth and Decay.

Amyloid-beta (Aß42) aggregates are characteristic Alzheimer's disease signatures, but probing how their nanoscale architectures influence their growth and decay remains challenging using current technologies. Here, we apply time-lapse single-molecule orientation-localization microscopy (SMOLM) to measure the orientations and rotational "wobble" of Nile blue (NB) molecules transiently binding to Aß42 fibrils. We correlate fibril architectures measured by SMOLM with their growth and decay over the course of 5 to 20 min visualized by single-molecule localization microscopy (SMLM). We discover that stable Aß42 fibrils tend to be well-ordered and signified by well-aligned NB orientations and small wobble. SMOLM also shows that increasing order and disorder are signatures of growing and decaying fibrils, respectively. We also observe SMLM-invisible fibril remodeling, including steady growth and decay patterns that conserve ß-sheet organization. SMOLM reveals that increased fibril architectural heterogeneity is correlated with dynamic remodeling and that large-scale fibril remodeling tends to originate from strongly heterogeneous local regions.

Gate Modulation of Dissipationless Nonlinear Quantum Geometric Current in 2D Te.

Two-dimensional trigonal tellurium (2D Te), a narrow-bandgap semiconductor with a bandgap of approximately 0.3 eV, hosts Weyl points near the band edge and exhibits a narrow, strong Berry curvature dipole (BCD). By applying a back-gate bias to align the Fermi level with the BCD, a sharp increase in the dissipationless transverse nonlinear Hall response is observed in 2D Te. Gate modulation of the BCD demonstrates an on/off ratio of 104 and a responsivity of nearly 106 V/W, while the longitudinal current induced by band modulation reaches an on/off ratio of about 10. This current is sustained up to 200 K, exhibiting a change of 3 orders of magnitude. The inclusion of both transistor action and rectification enhances the temperature sensitivity of the dissipationless Hall current, offering potential applications in electrothermal detectors and sensors and highlighting the significance of topological properties in advancing electronic applications.

Manipulative Single Electric Dipole with Spontaneous Translational Symmetry Breaking in a Two-Dimensional Crystal.

It is widely acknowledged that quantum entities with minimal mass cannot undergo spontaneous symmetry breaking due to strong quantum fluctuations. Here, we report the discovery of a positionally settled single electric dipole that can be manipulated and electrically polarized in a monolayer CoCl2-graphite heterostructure, which demonstrates an unprecedented example of spontaneous lattice-translational-symmetry breaking. Scanning tunneling microscopy and atomic force microscopy show that the solitons are intrinsic paraelectric dipoles driven by synchronous charge-lattice distortion around individual CoCl6 octahedrons. Both the dipole moment and lateral position of the soliton can be manipulated by the electric field exerted from the tip, which offers polarity-switchable and layout-designable electrostatic potential landscapes that determine the band bending configuration. This study exemplifies a brand-new type of local charge-lattice order, appealing for further research on the mechanism underlying the soliton robustness, and the electrically and positionally controllable single dipole supports the feasibility of band tailoring in device applications.

Nonlinear Electrical Transport Unveils Fermi Surface Malleability in a Moiré Heterostructure.

Van Hove singularities enhance many-body interactions and induce collective states of matter ranging from superconductivity to magnetism. In magic-angle twisted bilayer graphene, van Hove singularities appear at low energies and are malleable with density, leading to a sequence of Lifshitz transitions and resets observable in Hall measurements. However, without a magnetic field, linear transport measurements have limited sensitivity to the band's topology. Here, we utilize nonlinear longitudinal and transverse transport measurements to probe these unique features in twisted bilayer graphene at zero magnetic field. We demonstrate that the nonlinear responses, induced by the Berry curvature dipole and extrinsic scattering processes, intricately map the Fermi surface reconstructions at various fillings. Importantly, our experiments highlight the intrinsic connection of these features with the moiré bands. Beyond corroborating the insights from linear Hall measurements, our findings establish nonlinear transport as a pivotal tool for probing band topology and correlated phenomena.

Interfacial Passivation Engineering for Highly Efficient Quantum Dot Light-Emitting Diodes via Aromatic Amine-Functionalized Dipole Molecules.

Blue quantum dot (QD) light-emitting diodes (QLEDs) exhibit unsatisfactory operational stability and electroluminescence (EL) properties due to severe nonradiative recombination induced by large numbers of dangling bond defects and charge imbalance in QD. Herein, dipolar aromatic amine-functionalized molecules with different molecular polarities are employed to regulate charge transport and passivate interfacial defects between QD and the electron transfer layer (ETL). The results show that the stronger the molecular polarity, especially with the -CF3 groups possessing a strong electron-withdrawing capacity, the more effective the defect passivation of S and Zn dangling bonds at the QD surface. Moreover, the dipole interlayer can effectively reduce electron injection into QD at high current density, enhancing charge balance and mitigating Joule heat. Finally, blue QLEDs exhibit a peak external quantum efficiency (EQE) of 21.02% with an operational lifetime (T50 at 100 cd m-2) exceeding 4000 h.

Achieving Ideal Magnetic Light Emission with Electric-Type Emitters.

Optical magnetic dipole (MD) emission predominantly relies on emitters with significant MD transitions, which, however, rarely exist in nature. Here, we propose a strategy to transform electric dipole (ED) emission to a magnetic one by elegantly coupling an ED emitter to a silicon nanoparticle exhibiting a strong MD resonance. This emission mode transformation enables an artificially ideal magnetic dipole source with an MD purity factor of up to 99%. The far-field emission patterns of such artificial MD sources were experimentally measured, which unambiguously resolved their magnetic-type emission origin. This study opens the path to achieving ideal magnetic dipole emission with nonmagnetic emitters, largely extending the availability of magnetic light emitters conventionally limited by nature. Beyond the fundamental significance in science, we anticipate that this study will also facilitate the development of magnetic optical nanosource and enable potential photonic applications relying on magnetic light emission.

Vibrational Coupling Infrared Nanocrystallography.

Coupling between molecular vibrations leads to collective vibrational states with spectral features sensitive to local molecular order. This provides spectroscopic access to the low-frequency intermolecular energy landscape. In its nanospectroscopic implementation, this technique of vibrational coupling nanocrystallography (VCNC) offers information on molecular disorder and domain formation with nanometer spatial resolution. However, deriving local molecular order relies on prior knowledge of the transition dipole magnitude and crystal structure of the underlying ordered phase. Here we develop a quantitative model for VCNC by relating nano-FTIR collective vibrational spectra to the molecular crystal structure from X-ray crystallography. We experimentally validate our approach at the example of a metal organic porphyrin complex with a carbonyl ligand as the probe vibration. This framework establishes VCNC as a powerful tool for measuring low-energy molecular interactions, wave function delocalization, nanoscale disorder, and domain formation in a wide range of molecular systems.

Ultrahigh-Q Metasurface Transparency Band Induced by Collective-Collective Coupling.

The metasurface analogue of electromagnetically induced transparency (EIT) provides a chip-scale platform for achieving light delay and storage, high Q factors, and greatly enhanced optical fields. However, the literature relies on the coupling between localized and localized or localized and collective resonances, limiting the Q factor and related performance. Here, we report a novel approach for realizing collective EIT-like bands with a measured Q factor reaching 2750 in silicon metasurfaces in the near-infrared regime, exceeding the state of the art by more than 5 times. It employs the coupling between two collective resonances, the Mie electric dipole surface lattice resonance (SLR) and the out-of-plane/in-plane electric quadrupole SLR (EQ-SLR). Remarkably, the collective EIT-like resonance can have diverging Q factor and group delay due to the bound state in the continuum characteristics of the in-plane EQ-SLR. With these findings, our study opens a new route for tailoring light flow in metasurfaces.

Atomic-Site-Dependent Pairing Gap in Monolayer FeSe/SrTiO3(001)-(√13 × âˆš13).

The interfacial FeSe/TiO2-δ coupling induces high-temperature superconductivity in monolayer FeSe films. Using cryogenic atomically resolved scanning tunneling microscopy/spectroscopy, we obtained atomic-site dependent surface density of states, work function, and the pairing gap in the monolayer FeSe on the SrTiO3(001)-(√13 × âˆš13)-R33.7° surface. Our results disclosed the out-of-plane Se-Fe-Se triple layer gradient variation, switched DOS for Fe sites on and off TiO5□, and inequivalent Fe sublattices, which gives global spatial modulation of pairing gap contaminants with the (√13 × âˆš13) pattern. Moreover, the coherent lattice coupling induces strong inversion asymmetry and in-plane anisotropy in the monolayer FeSe, which is demonstrated to correlate with the particle-hole asymmetry in coherence peaks. These results disclose delicate atomic-scale correlations between pairing and lattice-electronic coupling in the Bardeen-Cooper-Schrieffer to Bose-Einstein condensation crossover regime, providing insights into understanding the pairing mechanism of multiorbital superconductivity.

Three-dimensional representation of the pure electric-dipole and the mixed first hyperpolarizabilities: The modified unit sphere representation.

In this work, the theory of the modified unit sphere representation (mUSR) has been proposed as a computational tool suitable for the three-dimensional representation of the pure electric-dipole [ ß λ µ ν ( - 2 ω ; ω , ω ) ] as well as of the mixed electric-dipole/magnetic-dipole [ α J λ µ ν ( - 2 ω ; ω , ω ) and ß J λ µ ν ( - 2 ω ; ω , ω ) ] or electric-dipole/electric-quadrupole [ α K λ µ ν o ( - 2 ω ; ω , ω ) and ß K λ µ ν o ( - 2 ω ; ω , ω ) ] first hyperpolarizabilities. These five quantities are Cartesian tensors and they are responsible for the chiral signal in the chiroptical version of the hyper-Rayleigh scattering (HRS) spectroscopy, namely the HRS optical activity (HRS-OA) spectroscopy. For the first time, for each hyperpolarizability, alongside with the three-dimensional representation of the whole (i.e., reducible) Cartesian tensors, the mUSRs are developed for each of the irreducible Cartesian tensors (ICTs) that constitute them. This scheme has been applied to a series of three (chiral) hexahelicene molecules containing different degrees of electron-withdrawing (quinone) groups and characterized by the same (positive) handedness. For these molecules, the mUSR shows that, upon substitution, the most remarkable qualitative and semi-quantitative (enhancement of the molecular responses) effects are obtained for the pure electric-dipole and for the mixed electric-dipole/magnetic-dipole hyperpolarizabilities.

Dipole-Dipole Tuned Electronic Reconfiguration of Defective Carbon Sites for Efficient Oxygen Reduction into H2O2.

Metal-free carbon-based materials are one of the most promising electrocatalysts toward 2-electron oxygen reduction reaction (2e-ORR) for on-site production of hydrogen peroxide (H2O2), which however suffer from uncontrollable carbonizations and inferior 2e-ORR selectivity. To this end, a polydopamine (PDA)-modified carbon catalyst with a dipole-dipole enhancement is developed via a calcination-free method. The H2O2 yield rate outstandingly reaches 1.8 mol gcat -1 h-1 with high faradaic efficiency of above 95% under a wide potential range of 0.4-0.7 VRHE, overwhelming most of carbon electrocatalysts. Meanwhile, within a lab-made flow cell, the synthesized ORR electrode features an exceptional stability for over 250 h, achieved a pure H2O2 production efficacy of 306 g kWh-1. By virtue of its industrial-level capabilities, the established flow cell manages to perform a rapid pulp bleaching within 30 min. The superior performance and enhanced selectivity of 2e-ORR is experimentally revealed and attributed to the electronic reconfiguration on defective carbon sites induced by non-covalent dipole-dipole influence between PDA and carbon, thereby prohibiting the cleavage of O-O in OOH intermediates. This proposed strategy of dipole-dipole effects is universally applicable over 1D carbon nanotubes and 2D graphene, providing a practical route to design 2e-ORR catalysts.