Abstract
2D spontaneous valley polarization attracts great interest both for its fundamental physics and for its potential applications in advanced information technology, but it can only be obtained ...from inversion asymmetric single-layer crystals, while the possibility to create 2D spontaneous valley polarization from inversion symmetric single-layer lattices remains unknown. Here, starting from inversion symmetric single-layer lattices, a general design principle for realizing 2D spontaneous valley polarization based on van der Waals interaction is mapped out. Using first-principles calculations, we further demonstrate the feasibility of this design principle in a real material of T-FeCl
2
. More remarkably, such design principle exhibits the additional exotic out-of-plane ferroelectricity, which could manifest many distinctive properties, for example, ferroelectricity-valley coupling and magnetoelectric coupling. The explored design-guideline and phenomena are applicable to a vast family of 2D materials. Our work not only opens up a platform for 2D valleytronic research but also promises the fundamental research of coupling physics in 2D lattices.
Creating a finite band gap, injecting electronic spin, and finding a suitable substrate are the three important challenges for building graphene-based devices. Here, first-principles calculations are ...performed to investigate the electronic and magnetic properties of graphene adsorbed on the (111) surface of diamond, which is synthesized experimentally Nature 472. 74 (2011) (http://dx.doi.org/10.1038/nature09979); J. Appl. Phys. 110, 044324 (2011) (http://dx.doi.org/10.1063/1.3627370); Nano Lett. 12, 1603 (2012) (http://dx.doi.org/10.1021/nl204545q); ACS Nano 6. 1018(2012) (http://dx.doi.org/10.1021/nn204362p). Our results reveal that the graphene adsorbed on the diamond surface is a semiconductor with a finite gap depending on the adsorption arrangements due to the variation of on-site energy induced by the diamond surface, with the extra advantage of maintaining main characters of the linear band dispersion of graphene. More interestingly, different from typical graphene/semiconductor hybrid systems, we find that electronic spin can arise "intrinsically" in graphene owing to the exchange proximity interaction between electrons in graphene and localized electrons in the diamond surface rather than the characteristic graphene states. These predications strongly revive this new synthesized system as a viable candidate to overcome all the aforementioned challenges, providing an ideal platform for future graphene-based electronics.
Granular flow are considered as the one of the most hazardous geological disasters in mountainous area. Multi-slit structure including one or more slits could partially block the granular flow and ...thus allow downstream flow at a reduced rate, have played a vital role in granular flow geohazard mitigation. This study conducted a series of discrete element method (DEM) models to investigate the interaction between dry granular flow and multi-slit structures (dual-slit structures in this study), and characterize the regulation functions of multi-slit structures. The dynamics process of flow-slit structure interaction and the effects of granular arches in multi-slit structures has been explicitly analyzed. Based on the analyses, a further modified Beverloo law considering the contraction behaviors is proposed to quantify the relationship between the mass outflow rate and relative slit size. The simulation findings show that both the slit size, slit numbers and slit separation have a significant impact on the regulating functions, such as pile-up height, mass outflow rate, and grain-trapping efficiency. In addition, it was found that, the shearing effect of the particles between the two nearby slits, the forming of the granular arches and the Froude characteristics might together influence the flow-slit interaction process, a key value of 4 for relative slit separation under a lower Froude number (5.86, in this study) was found to offer a reference for multi-slit structure scientific optimization design.
•The functions of dual-slit structures for intercepting and regulating rapid dry granular flows were systematically investigated.•The regulating function of dual-slit structures is controlled by the shearing effect of the particles between the two nearby slits, the forming of the granular arches and the Froude characteristics.•For a lower Froude number, the relative slit separation L/δ = 4 is a critical value for dual-slit structure.
DNA replication stress is often defined by the slowing or stalling of replication fork progression leading to local or global DNA synthesis inhibition. Failure to resolve replication stress in a ...timely manner contribute toward cell cycle defects, genome instability and human disease; however, the mechanism for fork recovery remains poorly defined. Here, we show that the translesion DNA polymerase (Pol) kappa, a DinB orthologue, has a unique role in both protecting and restarting stalled replication forks under conditions of nucleotide deprivation. Importantly, Pol kappa-mediated DNA synthesis during hydroxyurea (HU)-dependent fork restart is regulated by both the Fanconi Anemia (FA) pathway and PCNA polyubiquitination. Loss of Pol kappa prevents timely rescue of stalled replication forks, leading to replication-associated genomic instability, and a p53-dependent cell cycle defect. Taken together, our results identify a previously unanticipated role for Pol kappa in promoting DNA synthesis and replication stress recovery at sites of stalled forks.
The geometric and electronic structures of graphene adsorption on MoS(2) monolayer have been studied by using density functional theory. It is found that graphene is bound to MoS(2) with an ...interlayer spacing of 3.32 Å and with a binding energy of -23 meV per C atom irrespective of adsorption arrangement, indicating a weak interaction between graphene and MoS(2). A detailed analysis of the electronic structure indicates that the nearly linear band dispersion relation of graphene can be preserved in MoS(2)/graphene hybrid accompanied by a small band-gap (2 meV) opening due to the variation of on-site energy induced by MoS(2). These findings are useful complement to experimental studies of this new synthesize system and suggest a new route to facilitate the design of devices where both finite band-gap and high carrier mobility are needed.
Na‐ion Batteries have been considered as promising alternatives to Li‐ion batteries due to the natural abundance of sodium resources. Searching for high‐performance anode materials currently becomes ...a hot topic and also a great challenge for developing Na‐ion batteries. In this work, a novel hybrid anode is synthesized consisting of ultrafine, few‐layered SnS2 anchored on few‐layered reduced graphene oxide (rGO) by a facile solvothermal route. The SnS2/rGO hybrid exhibits a high capacity, ultralong cycle life, and superior rate capability. The hybrid can deliver a high charge capacity of 649 mAh g−1 at 100 mA g−1. At 800 mA g−1 (1.8 C), it can yield an initial charge capacity of 469 mAh g−1, which can be maintained at 89% and 61%, respectively, after 400 and 1000 cycles. The hybrid can also sustain a current density up to 12.8 A g−1 (≈28 C) where the charge process can be completed in only 1.3 min while still delivering a charge capacity of 337 mAh g−1. The fast and stable Na‐storage ability of SnS2/rGO makes it a promising anode for Na‐ion batteries.
A SnS2/rGO hybrid with a plate‐on‐sheet architecture exhibits a high capacity, superior cycling stability and excellent rate capability. The hybrid delivers an initial capacity of 469 mAh g−1 at 800 mA g−1 and keeps at 61% after 1000 cycles. At 12.8 A g−1 (28 C), it still yields a charge capacity of 337 mAh g−1.
The centrifuge modeling of the impact dynamics of high-speed granular flows is important for understanding debris–barrier interactions. However, it remains challenging owing to the Coriolis effect, ...which makes the physical modeling results complex and difficult to interpret. Based on centrifuge modeling and the discrete element method (DEM), we investigated the impact dynamics of dry granular flows under dilative and compressive Coriolis conditions, and the Coriolis effect on the granular impact was revealed. The results reveal that the influence of the Coriolis effect is extremely complex, and we found that it is difficult to determine the most unfavorable test conditions in centrifuge modeling. When the magnitude of the total impact force on the barrier was considered, the influence of the compressive Coriolis force was less significant. The dynamic impact of granular flow under the dilative Coriolis condition was enhanced but closer to the results not affected by the Coriolis effect. However, when focusing on the acting point of the resultant impact force on the barrier, the influence of dilative and compressive Coriolis conditions was not obvious. Therefore, when carrying out a physical modeling test using a centrifuge, the objective of the test should be clarified first, and the influence of the Coriolis effect should be properly evaluated according to the test content to select the appropriate Coriolis condition. If a detailed evaluation of the Coriolis effect is not available, the dilative Coriolis condition is recommended for testing.
•Comprehensive assessment of Coriolis effect on granular impact is presented.•Debris–barrier interaction is promoted by dilative Coriolis force.•Coriolis effect does not affect the acting point of resultant impact force.•Dilative Coriolis condition is recommended for physical impact testing.
The layer Hall effect (LHE) is of fundamental and practical importance in condensed-matter physics and material science; however, it was rarely observed and usually based on the paradigms of ...persistent electric field and sliding ferroelectricity. Here, a new mechanism of LHE is proposed by coupling layer physics with multiferroics using symmetry analysis and a low-energy k·p model. Due to time-reversal symmetry breaking and valley physics, the Bloch electrons on one valley will be subject to a large Berry curvature. This combined with inversion symmetry breaking gives rise to layer-polarized Berry curvature and can force the electrons to deflect in one direction of a given layer, thereby generating the LHE. We demonstrate that the resulting LHE is ferroelectrically controllable and reversible. Using first-principles calculations, this mechanism and predicted phenomena are verified in the multiferroic material of bilayer Co2CF2. Our finding opens a new direction for LHE and 2D materials research.
Photocatalytic overall water-splitting is known as one of most promising methods to alleviate energy crisis. Searching for stable and efficient photocatalysts plays a critical role in this process. ...Here, we propose a novel class of Janus chromium dichalcogenide (CrXY, X/Y = S, Se, and Te) monolayers serving as efficient photocatalysts for overall water-splitting under infrared light irradiation. We reveal that these Janus monolayers harbor an intrinsic dipole, which promotes the spatial separation of photogenerated carriers. More significantly, these systems exhibit suitable band gaps as well as band edge positions, enabling preeminent infrared optical absorption and high carrier mobility. Furthermore, the nonradiative recombination of photoinduced charge carriers in CrXY monolayers is evaluated based on time domain density functional theory. The obtained long-lived excited carriers (∼2 ns) are even comparable with that in transition-metal dichalcogenide heterostructures, which benefits for the photocatalytic reaction with high efficiency. Our results provide a new guidance for designing brand new photocatalytic systems with broad optical absorption and low carrier recombination.
Searching for high-performance electrode materials is one of the most effective ways to improve the energy density of current lithium-ion batteries. Using first-principles calculations, we reveal ...that pentagonal BN2 (Penta-BN2) can serve as a compelling anode material for lithium-ion batteries. Penta-BN2 harbors intrinsic metallic nature before and after lithiation, showing excellent electrical conductivity. Significantly, the fully lithiated phase of Penta-BN2 is Li3BN2, corresponding to an ultra-high theoretical capacity of 2071 mAh g–1, superior to the capacity of most of the previously reported two-dimensional candidates. Meanwhile, the open-circuit voltage and diffusion barrier height of Penta-BN2 are found to be fascinatingly low. Moreover, in light of its small Young’s modulus and robust lattice toward lithiation, Penta-BN2 can accommodate volume changes during the charging–discharging processes, remarkably beneficial for fabricating flexible electrodes.
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