Weak Dipole Moments Research Articles

Weak paleointensities from 1.6 Ga Greenland dykes: Further evidence for a billion-year period of paleomagnetic dipole low during the Paleoproterozoic

The Paleoproterozoic era is the longest in Earth's history, with significant changes hypothesised to have occurred in the deep Earth's physical and chemical conditions at this time. It has been suggested that the paleomagnetic field became weaker at this time (∼2.4 Ga) and remained weak for the next billion years. Paleomagnetism is intrinsically linked to, and is able to inform on, ancient deep Earth processes; a weak dipole strength sustained over this time period may have implications for both core and mantle evolution.We test this hypothesis here in a two-fold approach: (1) A paleointensity study on the widespread ca. 1.6 Ga diabase/dolerite Melville Bugt dyke swarm. The swarm extends along the west coast of Greenland for more than 1000 km and intruded over ∼13 million years, capturing polarity reversals of Earth's magnetic field. (2) A detailed statistical analysis on the long-term trend in average dipole moment from an improved paleointensity dataset (PINT.org) that has recently undergone a major update.Five of the Greenland dykes produce paleointensity results ranging from 1.4 μT to 5.1 μT (virtual dipole moment range 0.3–1.2 × 1022 Am2) during the mid-point of this extended period of ‘dipole low’. Our statistical study robustly confirms that this one-billion-year period was indeed associated with an anomalously weak dipole moment (2.7 × 1022 Am2) relative to 500-million-year intervals before and after, which were almost twice as strong. Sampling of more geographically diverse rocks from this time is needed to yield a clear picture of the long-term time evolution of the dipole moment.

Hierarchical self-constructed molecular layers of small bifunctional molecules with strong molecular dipole moments for improvement of quantum efficiency in inorganic quantum dots

Hierarchically structured self-assembled molecular layers are functionally versatile and structurally tunable, which are nanoscale molecular building blocks with a wide range of applications from biosensing systems to optoelectronic devices. Herein, we present a facile and effective strategy to fabricate hierarchical self-constructed molecular layers comprising small bifunctional molecules with strong molecular dipole moments for improvement of quantum efficiency in inorganic quantum dots (QDs) by using the cooperative interfacial self-assembly of hydrophilic bifunctional molecules on the polar electrode surface. The spontaneous construction of nanostructured molecular layers with different molecular dipole moments was simply achieved through solution-dipping and in situ interfacial self-organization of 3-mercaptopropionic acid or 1-propanethiol molecules on the surface of indium tin oxide (ITO) anode. It is experimentally revealed that these functional molecules formed uniform and ultrathin self-constructed molecular nanolayers on the ITO surface via covalent bonding, where bifunctional 3-mercaptopropionic acid molecules induced a polar molecular surface of thiol groups with strong dipole moments, whereas 1-propanethiol molecules formed a relatively hydrophobic surface of short alkyl chains with weak dipole moments. In addition, the nanoscale ultrathin nature of these molecular layers afforded high visible light transmittance comparable to that of pristine ITO substrate. The electro-optical properties of the QD cells revealed that hierarchical self-constructed molecular nanolayer with strong molecular dipole moments exhibited superior current and luminescent properties with a 162% improvement in external quantum efficiency relative to those of a conventional QD device without molecular layer. Furthermore, the self-assembled molecular nanolayer of 3-mercaptopropionic acid exhibited a higher luminescent efficiency than 1-propanethiol-based nanolayer owing to the increased hole mobility of thiol-based molecular layer with strong dipole moments.

Strong coupling of plasmonic bright and dark modes with two eigenmodes of a photonic crystal cavity.

Dark modes represent a class of forbidden transitions or transitions with weak dipole moments between energy states. Due to their low transition probability, it is difficult to realize their interaction with light, let alone achieve the strong interaction of the modes with the photons in a cavity. However, by mutual coupling with a bright mode, the strong interaction of dark modes with photons is possible. This type of mediated interaction is widely investigated in the metamaterials community and is known under the term electromagnetically induced transparency (EIT). Here, we report strong coupling between a plasmonic dark mode of an EIT-like metamaterial with the photons of a 1D photonic crystal cavity in the terahertz frequency range. The coupling between the dark mode and the cavity photons is mediated by a plasmonic bright mode, which is proven by the observation of a frequency splitting which depends on the strength of the inductive interaction between the plasmon bright and dark modes of the EIT-like metamaterial. In addition, since the plasmonic dark mode strongly couples with the cavity dark mode, we observes four polariton modes. The frequency splitting by interaction of the four modes (plasmonic bright and dark mode and the two eigenmodes of the photonic cavity) can be reproduced in the framework of a model of four coupled harmonic oscillators.

Ab initio study: Investigating the adsorption behaviors of polarized greenhouse gas molecules on pillar[5]arenes

Supramolecular organic frameworks (SOFs) based on Pillar[5]arenes (P[5]A) have shown great potential in capturing and separating greenhouse gases. In this study, we investigate the adsorption behaviors of other environmentally harmful gas molecules, including NO, NH3, CO, and NO2 on pillar[5]arenes (P[5]A) using DFTB and DFT calculations. The P[5]A structures exhibit the capability to adsorb including NO, NH3, CO, and NO2 at both the cavity site and OH group, facilitated by π-π interactions and hydrogen bonding. CO exhibits the lowest binding energy among the studied gases, primarily due to its weak dipole moment. In contrast, the cavity-in positions for NO2 and NH3, characterized by high polarization, exhibit the highest adsorption energies. The adsorption energies at the top-out positions are relatively similar for all gases examined. These findings provide valuable insights for the targeted design and optimization of P[5]A, enabling its potential applications in effectively capturing toxic gases.

Searching the anomalous electromagnetic and weak dipole moments of the top quark at the bestest little Higgs model

Searching the anomalous electromagnetic and weak dipole moments of the top quark at the bestest little Higgs model

Computational study on nickel doped encapsulated Mg, K, Ca on pristine C24 nanocage for gas sensing applications

Intense attention have been channeled into environmental sustainability due to the high emission of greenhouse gases therefore, this investigatiom focuses on the adsorption and sensing properties of nickel doped encapsulated Mg, K, Ca on pristine C24 nanocage for CO2, NO2 and SO2 gases using density functional theory (DFT) method. Two adsorption models were designed due to the shape of the gas molecules, interacting to the doped atom, the DFT/TPSSh/Gen method was utilized to explore the adsorption properties from the perspective of geometry analysis, adsorption energy (Eads), electronic properties, visual study of weak interactions, dipole moment, and recovery time for reusability were considered. This work incorporated a comprehensive reference for the selectivity of the adsorbents’ modification towards the effective sensing of these toxic gases. Thus, the electronic properties confirms the conductivity on modification of surface with dopant. Also, the nature of interaction as reveal by the QTAIM analysis was non-covalent in nature and was further confirmed by the analysis of the non-covalent interaction (NCI). Moreso, the reusability analysis confirms surface sensing properties. Adsorption energies; −3.67, −2.48, −3.89, −2.50, −3.82, −3.67 eV, were reported for NO2–Ni@MgC, CO2–Ni@KC, NO2–Ni@KC, CO2–Ni@CaC, NO2–Ni@CaC, SO2–Ni@CaC respectively. Moreover, the aforementioned analyses demonstrate the significant impact on the adsorption models most especially NO2–Ni@KC. Hence, Ni@KC and Ni@CaC shows promising sensitivity towards the gas molecules than Ni@MgC. Based on our theoretical results, the encapsulation of K, Ca, Mg, and late transition metal dopant enhances the adsorbents, which induced the improvement in surface properties. The highest Eads was observed at M3a at −5.11 eV and the least at M1 at −2.11 eV all for SO2 adsorption.

Research on the electromagnetic and weak dipole moments of the tau-lepton at the Bestest Little Higgs Model

In this paper, using the Bestest Little Higgs Model (BLHM) we calculate at the one-loop level the contributions to the Anomalous Magnetic Dipole Moment (AMDM) and Anomalous Weak Magnetic Dipole Moment (AWMDM) of the tau-lepton. The implications from this model are studied, emphasizing the contributions of the new physics induced by the new scalar and vector bosons of the BLHM: S_i=H_0, A_0, phi ^{0}, eta ^{0}, sigma , H^{pm }, phi ^{pm }, eta ^{pm }, and V_i=Z', W'^{pm } because these quantify the new physics. With these new contributions, we estimated bounds on the real and imaginary parts of the AMDM and AWMDM of the tau-lepton. Our study complements other one-loop-level research performed on models beyond the Standard Model.

Weak dipole moments of the top-quark at the Bestest Little Higgs model

Weak dipole moments of the top-quark at the Bestest Little Higgs model

Extremely weak early Cambrian dipole moment similar to Ediacaran: Evidence for long-term trends in geomagnetic field behaviour?

Paleointensity data can yield insight on the state of the geodynamo, providing constraints on deep Earth events and enabling analysis of long-term trends in the paleomagnetic field. The Ediacaran (635 Ma–539 Ma) is a period of discrepant paleomagnetic behaviour that was recently characterised by sustained, extremely weak, paleointensity. The interval also coincides with some of the most recent estimates for Earth's inner core nucleation (ICN) age, determined from numerical geodynamo models and analysis of long-term paleointensity data. However, the field strength during the subsequent Cambrian period (540 Ma–485 Ma) is largely unknown with almost no data.Here, we provide high-quality paleointensity results for the Cambrian. A Grenville dyke (∼590 Ma) that was baked by the Chatham-Grenville stock (532 Ma), slowly cooled at a rate controlled by the stock and recorded the paleointensity averaged over this interval (up to several tens of thousands of years). The characteristic paleomagnetic directions of the dyke are well-defined and consistent with those previously obtained from the Chatham-Grenville and Mont Riguad stocks.Paleointensity data were obtained using multiple methods and indicate an extremely weak field during a period coincidental with evidence for hyper-reversing activity extending into the late Cambrian. The dipole strength is similar to that of the ‘ultra-weak’ Ediacaran and may suggest that this paleomagnetic behaviour persisted into the Cambrian. The cause of this weak-field interval remains enigmatic but an approximate 200-million-year quasi-periodicity in dipole strength extending across the entire Phanerozoic is not ruled out.

Limiting capabilities of two-dimensional plasmonics in electromagnetic wave detection

Plasmons in two-dimensional electron systems (2DESs) feature ultrastrong confinement and are expected to efficiently mediate the interactions between light and charge carriers. Despite these expectations, the electromagnetic detectors exploiting 2D plasmon resonance have been so far inferior to their nonresonant counterparts. Here, we theoretically analyze the origin of these failures, and suggest a proper niche for 2D plasmonics in electromagnetic wave detection. We find that a confined 2DES supporting plasmon resonance has an upper limit of absorption cross section, which is identical to that of simple metallic dipole antenna. Small size of plasmonic resonators implies their weak dipole moments and impeded coupling to free-space radiation. Achieving the ``dipole limit'' of the absorption cross section in isolated 2DES is possible either at unrealistically long carrier momentum relaxation times, or at resonant frequencies below units of terahertz. We further show that amendment of even small metal contacts to 2DES promotes the coupling and reduces the fundamental mode frequency. The contacted resonators can still have deep-subwavelength size. They can be merged into compact arrays of detectors responding resonantly to multiple frequencies. Such arrays may find applications in multichannel wireless communications, hyper-spectral imaging, and energy harvesting.

Weak dipole moments of heavy fermions with flavor violation induced by Z′ gauge bosons

A calculation of weak dipole moments of charged fermions of the standard model at the one-loop level, in the context of a general effective extended neutral current model with flavor changing vertices, is presented. We give numerical predictions for the anomalous weak magnetic dipole moment , and the weak electric dipole moment (WEDM) , for the τ lepton and t quark. For several Z′ gauge bosons considered, we find that, for the τ lepton, the best prediction for the real part of is of the order of 10−9, while the imaginary part is four orders of magnitude below. The highest value for the WEDM, , corresponds to 10−26 e cm, for its real part, and the imaginary part is three orders of magnitude below. Moreover, we found for the top quark, that the best prediction for the real part of is of the order of 10−7 and its imaginary part is of the order of 10−11. We also found that is of the order of 10−26 e cm for its real part, and its imaginary part can be as high as 10−31 e cm.

Crystal Facet‐Controlled Efficient SnS Photocathodes for High Performance Bias‐Free Solar Water Splitting (Adv. Sci. 21/2021)

Photoelectrochemical Solar Water Splitting In article number 2102458 by Ho Won Jang, Jooho Moon, and co workers, performance bias-free solar water splitting is reported. Sulfur precursor with a weak dipole moment produces high-quality dense SnS nanoplates with enlarged favorable crystallographic facets, suppressing anisotropic growth. Ga2O3 interlayered SnS photocathode efficiently improves charge transport kinetics without charge trapping. The high-performance SnS photocathode represents a promising platform for photoelectrochemical solar water splitting.

Crystal Facet-Controlled Efficient SnS Photocathodes for High Performance Bias-Free Solar Water Splitting.

To achieve a high solar‐to‐hydrogen (STH) conversion efficiency, delicate strategies toward high photocurrent together with sufficient onset potential should be developed. Herein, an SnS semiconductor is reported as a high‐performance photocathode. Use of proper sulfur precursor having weak dipole moment allows to obtain high‐quality dense SnS nanoplates with enlarged favorable crystallographic facet, while suppressing inevitable anisotropic growth. Furthermore, the introducing Ga2O3 layer between SnS and TiO2 in SnS photocathodes efficiently improves the charge transport kinetics without charge trapping. The SnS photocathode reveals the highest photocurrent density of 28 mA cm−2 at 0 V versus the reversible hydrogen electrode. Overall solar water splitting is demonstrated for the first time by combining the optimized SnS photocathode with a Mo:BiVO4 photoanode, achieving a STH efficiency of 1.7% and long‐term stability of 24 h. High performance and low‐cost SnS photocathode represent a promising new material in the field of photoelectrochemical solar water splitting.

Colossal enhancement of the magnetic dipole moment by exploiting lattice coupling in metasurfaces

An artificial magnetic response is not only intellectually intriguing but also key to multiple applications. While previously suitably structured metallic particles and high-permittivity dielectric particles have been used for this purpose, here, we highlight the possibility of exploiting lattice effects to significantly enhance an intrinsically weak magnetic dipole moment of a periodically arranged scatterer. We identify the effective magnetic dipole moment as it is modulated by the lattice and coupled to other electromagnetic multipole moments the scatterer can sustain. Besides a more abstract consideration on the base of parametrized Mie coefficients to study the theoretical upper limit, we present an actual particle that shows an enhancement of the magnetic dipole moment by 100 with respect to what is attainable as a maximal value for an isolated particle.

Magnetic properties of NH4Al(SO4)2•12H2O: Evidence of glass behavior based on proton orbitals

The polarity of the magnetic susceptibility χ(T) of ammonium alum NH4Al(SO4)2•12H2O single crystals below its ferroelectric Curie temperature TC is identified to depend only on the cooling rate. To explain this, we consider reorienting distorted NH4+ to carry weak magnetic and electric dipole moments that are linearly coupled. Slow cooling allows the dipole moments to align which enhances χ(T) to become positive. However, due to energy degeneracy of rotational motion and geometric frustration of the NH4+, faster cooling rates render the system to become an orientational glass state causing χ(T) to remain negative. Specific heat measurements also show the presence of excess entropy below a negative anomaly near 53 K. Our findings identify a possible new class of non-equilibrium system with potential applications in non-volatile memory devices.

Constraining EDM and MDM lepton dimension-five interactions in the electroweak sector

We investigate dimension-five Lorentz-violating (LV) nonminimal interactions in the electroweak sector, in connection with the possible generation of electric dipole moment (EDM), weak electric dipole moment (WEDM), magnetic dipole moment (MDM) and weak magnetic dipole moment (WMDM) for leptons. These couplings are composed of the physical fields in the Standard Model and LV tensors of ranks ranging from 1 to 4. The CPT-odd couplings do not generate EDM behavior nor provide the correct MDM signature, while the CPT-even ones are compatible with EDM and MDM behavior, being subject to improved constraining. Tau lepton experimental data is used to constrain the WEDM and WMDM couplings to the level of 10−4(GeV)−1, whereas electron MDM and EDM data are employed to improve constraints to the level of 10−10(GeV)−1 and 10−16(GeV)−1, respectively.

Beyond Chiral Organic (p-Block) Chromophores for Circularly Polarized Luminescence: The Success of d-Block and f-Block Chiral Complexes.

Chiral molecules are essential for the development of advanced technological applications in spintronic and photonic. The best systems should produce large circularly polarized luminescence (CPL) as estimated by their dissymmetry factor (glum), which can reach the maximum values of −2 ≤ glum ≤ 2 when either pure right- or left-handed polarized light is emitted after standard excitation. For matching this requirement, theoretical considerations indicate that optical transitions with large magnetic and weak electric transition dipole moments represent the holy grail of CPL. Because of their detrimental strong and allowed electric dipole transitions, popular chiral emissive organic molecules display generally moderate dissymmetry factors (10−5 ≤ glum ≤ 10−3). However, recent efforts in this field show that glum can be significantly enhanced when the chiral organic activators are part of chiral supramolecular assemblies or of liquid crystalline materials. At the other extreme, chiral EuIII- and SmIII-based complexes, which possess intra-shell parity-forbidden electric but allowed magnetic dipole transitions, have yielded the largest dissymmetry factor reported so far with glum ~ 1.38. Consequently, 4f-based metal complexes with strong CPL are currently the best candidates for potential technological applications. They however suffer from the need for highly pure samples and from considerable production costs. In this context, chiral earth-abundant and cheap d-block metal complexes benefit from a renewed interest according that their CPL signal can be optimized despite the larger covalency displayed by d-block cations compared with 4f-block analogs. This essay thus aims at providing a minimum overview of the theoretical aspects rationalizing circularly polarized luminescence and their exploitation for the design of chiral emissive metal complexes with strong CPL. Beyond the corroboration that f–f transitions are ideal candidates for generating large dissymmetry factors, a special attention is focused on the recent attempts to use chiral CrIII-based complexes that reach values of glum up to 0.2. This could pave the way for replacing high-cost rare earths with cheap transition metals for CPL applications.

A "Rigid-Flexible" Approach for Processable Perylene Diimide-Based Polymers: Influence of the Specific Architecture on the Morphological, Dielectric, Optical, and Electronic Properties.

Conjugation-break flexible spacers in-between π-conjugated segments were utilized herein toward processable perylene diimide (PDI)-based polymers. Aromatic-aliphatic PDI-based polymers were developed via the two-phase polyetherification of a phenol-difunctional PDI monomer and aliphatic dibromides. These polyethers showed excellent solubility and film-forming ability and deep lowest unoccupied molecular orbital (LUMO) levels (-4.0 to -3.85 eV), indicating the preservation of good electron-accepting character or characteristics, despite the non-conjugated segments. Their thermodynamic properties, local dynamics, and ionic conductivity demonstrate the suppression of PDI's inherent tendency for aggregation and crystallization, suggesting PDI-polyethers as versatile candidates for organic electronic applications. Their dynamics investigation using dielectric spectroscopy revealed weak dipole moments arising from the distortion of the planar perylene cores. Blends of the PDI-polyethers (as electron acceptors) with P3HT (as a potential electron donor component) showed UV-vis absorbances from 350 to 650 nm and a tendency of the PDI-polyethers to intertwine with rr-P3HT and restrain its high crystallization tendency.

Highly efficient unidirectional forward scattering induced by resonant interference in a metal-dielectric heterodimer.

We demonstrate that a metal-dielectric heterodimer structure can satisfy a nearly ideal first Kerker condition at a wavelength close to the resonance peak of the dimer, yielding efficient unidirectional forward scattering with a high forward-to-backward scattering ratio (≈48 dB) and remarkable enhancement of the forward scattering intensity (∼2.68 times compared to a single dielectric nanoparticle). Using a rigorous analytical dipole-dipole interaction model, the underlying mechanism is revealed, in which the originally weak electric dipole moment of the dimer is significantly enhanced owing to the strong resonant interference between the localized surface plasmon resonance of the metal and the Mie resonances of the dielectric material, which could up-match the magnetic dipole moment of the dimer at a wavelength close to the resonance peak, boosting the forward scattering efficiency. To achieve the optimal conditions, the sizes of the metal and dielectric constituents as well as the gap distance of the dimer have to be physically and delicately tuned to ensure a perfect match in both the amplitudes and phases of the electric and magnetic dipole moments of the dimer. On top of that, the loss of the heterodimer can be effectively suppressed to a level well below that of a pure metal nanoparticle, which further benefits the forward scattering efficiency. The flexibility in designing the dimer geometry and choosing metal-dielectric material combinations enables efficient unidirectional forward scattering in a broadband spectrum (UV to visible) with an intermediate gap distance (10-20 nm), greatly expanding the application scope. The proposed hybrid dimer could serve as a powerful and versatile building block in many emergent fields such as metasurfaces, nanoantennae, etc.

Terahertz detection of toxic gas using a photonic crystal fiber

Abstract The photon energies of molecules falling rightly into the terahertz region offers a high potential for gas detection. However, detecting gas at low concentration is difficult because of the weak dipole moments of gas in the terahertz region. Here, a unique structure of porous core photonic crystal fiber (PCF) sensor with a high sensitivity for gas detection is proposed. The dependences of the mode field distribution and the propagation loss of PCF sensor on the porosity are studied to optimize for a higher sensitivity. For the optimal PCF with a porosity of 50%, the mode field is strongly confined in the air holes in the core, and the propagation loss can reach as low as 0.013 dB/m. The detection of a toxic gas (hydrogen cyanide) is also investigated to demonstrate the sensing performance of the proposed PCF. A low concentration of 2 ppm under the standard atmosphere pressure (1 atm) can be detected based on the resonance frequency of the hydrogen cyanide. The length of the proposed PCF is just 100 mm, which is much shorter than the traditional optical fiber with several meters long. Our results provide a novel approach for the detection of toxic gas in air pollution monitoring using terahertz spectroscopy.