Controlling the crystal structure is a powerful approach for manipulating the fundamental properties of solids. In van der Waals materials, this control can be achieved by modifying the stacking ...order through rotation and translation between the layers. Here, we observed stacking-dependent interlayer magnetism in the two-dimensional (2D) magnetic semiconductor chromium tribromide (CrBr
), which was enabled by the successful growth of its monolayer and bilayer through molecular beam epitaxy. Using in situ spin-polarized scanning tunneling microscopy and spectroscopy, we directly correlate the atomic lattice structure with the observed magnetic order. Although the individual monolayer CrBr
is ferromagnetic, the interlayer coupling in bilayer depends on the stacking order and can be either ferromagnetic or antiferromagnetic. Our observations pave the way for manipulating 2D magnetism with layer twist angle control.
Layered antiferromagnetism is the spatial arrangement of ferromagnetic layers with antiferromagnetic interlayer coupling. The van der Waals magnet chromium triiodide (CrI3) has been shown to be a ...layered antiferromagnetic insulator in its few-layer form, opening up opportunities for various functionalities in electronic and optical devices. Here we report an emergent nonreciprocal second-order nonlinear optical effect in bilayer CrI3. The observed second-harmonic generation (SHG; a nonlinear optical process that converts two photons of the same frequency into one photon of twice the fundamental frequency) is several orders of magnitude larger than known magnetization-induced SHG and comparable to the SHG of the best (in terms of nonlinear susceptibility) two-dimensional nonlinear optical materials studied so far (for example, molybdenum disulfide). We show that although the parent lattice of bilayer CrI3 is centrosymmetric, and thus does not contribute to the SHG signal, the observed giant nonreciprocal SHG originates only from the layered antiferromagnetic order, which breaks both the spatial-inversion symmetry and the time-reversal symmetry. Furthermore, polarization-resolved measurements reveal underlying C2h crystallographic symmetry-and thus monoclinic stacking order-in bilayer CrI3, providing key structural information for the microscopic origin of layered antiferromagnetism. Our results indicate that SHG is a highly sensitive probe of subtle magnetic orders and open up possibilities for the use of two-dimensional magnets in nonlinear and nonreciprocal optical devices.
A photoresponsive organogel surface (POS), which integrates characteristics of the photothermal property of Fe3O4 nanoparticles and the low hysteresis feature of lubricant‐infused organogels, is ...shown. A photothermally induced dynamic temperature gradient can be formed rapidly at the location of near‐infrared‐light irradiation (NIR) on POS with suitable Fe3O4 nanoparticles content. Thus, various droplets (e.g., water, glycerol, ethylene glycol, propylene glycol, and ethanol) can be transported effectively and nimbly (e.g., along desired trajectories with controllable velocity and direction, even run uphill and deliver solid particles). This work reveals a synergistic effect between the asymmetrical droplet deformation and the inside Marangoni flows, which forms a unique driving force for droplet transport with high efficiency. This finding offers insight into the design of novel responsive interface materials for droplet transportation, which would be significant for laboratory‐on‐a‐chip contexts, mass transportation, and microengines.
A synergistic effect between asymmetrical droplet deformation and the inside Marangoni flows forms a unique driving force for droplet transport with high efficiency on photothermal organogel surfaces.
Lightweight and high-strength materials with high electromagnetic interference shielding performance are the best solution for electromagnetic pollution. However, the MXene film with extremely high ...electromagnetic interference shielding effectiveness cannot be extensively applied to the aerospace engineering because of its high density and low mechanical properties. Herein, a MXene/cellulose nanofiber (CNF) composite film with low density and high conductivity (24,875 S m
−1
) was prepared by using an ice crystal sacrificial template as a pore-forming agent and CNF as a structural reinforcement. The composite film with a small thickness effectively shielded electromagnetic waves since it has a continuous three-dimensional MXene conductive network framework, which serves as a rich interface to facilitate multiple reflections and absorption attenuation of electromagnetic waves. In addition, the absolute electromagnetic interference shielding effectiveness of the prepared film reached 9177 dB cm
2
g
−1
. The design concept and approaches adopted in this work are highly efficient and scalable, which provides a bright prospect for the development of the MXene/polymer composites with high electromagnetic interference shielding properties.
The emergence of 2D polarized materials, including ferromagnetic, ferrovalley, and ferroelectric materials, has demonstrated unique quantum behaviors at atomic scales. These polarization behaviors ...are tightly bonded to the new degrees of freedom (DOFs) for next generation information storage and processing, which have been dramatically developed in the past few years. Here, the basic 2D polarized materials system and related devices’ application in spintronics, valleytronics, and electronics are reviewed. Specifically, the underlying physical mechanism accompanied with symmetry broken theory and the modulation process through heterostructure engineering are highlighted. These summarized works focusing on the 2D polarization would continue to enrich the cognition of 2D quantum system and promising practical applications.
The distinct physical origin of 2D polarizations and modulation on degrees of freedom are comprehensively summarized based on the hysteresis behaviors and interface effects. The novel multifunctional polarized devices are discussed, from which perspectives and guidelines are proposed for developing “beyond Moore” integrated devices and circuits.
The steady-state spectra and fluorescence lifetimes are investigated under vacuum for methylammonium lead bromide and iodide (CH3NH3PbBr3 or MAPbBr3, and CH3NH3PbI3 or MAPbI3) thin films by stably ...controlling the sample temperature in the range of 78 K to 320 K. The transformation of spectrum features and lifetime components are proved to be quite sensitive to the temperatures in accordance with the phase transition of structures. Our work demonstrates that the halide anions I- and Br- lead to remarkable differences on optical characteristics. Due to the distinct behaviors of excitons, electron-hole pairs and free carriers in decay channels, MAPbI3 has much longer lifetime and higher low-temperature fluorescence efficiency than those of MAPbBr3. The findings provide possible choices for certain perovskites under various ambient temperature conditions to display photovoltaic or luminescent advantage.
Excitonic systems, facilitated by optical pumping, electrostatic gating or magnetic field, sustain composite particles with fascinating physics. Although various intriguing excitonic phases have been ...revealed via global measurements, the atomic-scale accessibility towards excitons has yet to be established. Here, we realize the ground-state interlayer exciton complexes through the intrinsic charge transfer in monolayer YbCl
/graphite heterostructure. Combining scanning tunneling microscope and theoretical calculations, the excitonic in-gap states are directly profiled. The out-of-plane excitonic charge clouds exhibit oscillating Rydberg nodal structure, while their in-plane arrangements are determined by moiré periodicity. Exploiting the tunneling probe to reflect the shape of charge clouds, we reveal the principal quantum number hierarchy of Rydberg series, which points to an excitonic energy-level configuration with unusually large binding energy. Our results demonstrate the feasibility of mapping out the charge clouds of excitons microscopically and pave a brand-new way to directly investigate the nanoscale order of exotic correlated phases.
Bilayer (BL) MoSe2 films grown by molecular-beam epitaxy (MBE) are studied by scanning tunneling microscopy and spectroscopy (STM/S). Similar to monolayer (ML) films, networks of inversion domain ...boundary (DB) defects are observed both in the top and bottom layers of BL MoSe2, and often they are seen spatially correlated such that one is on top of the other. There are also isolated ones in the bottom layer without companion in the top-layer and are detected by STM/S through quantum tunneling of the defect states through the barrier of the MoSe2 ML. Comparing the DB states in BL MoSe2 with that of ML film reveals some common features as well as differences. Quantum confinement of the defect states is indicated. Point defects in BL MoSe2 are also observed by STM/S, where ionization of the donor defect by the tip-induced electric field is evidenced. These results are of great fundamental interests as well as practical relevance of devices made of MoSe2 ultrathin layers.
The Digital Stress Scale (DSS) is used to measure digital stress, which is the perceived stress and anxiety associated with social media use. In this study, the Chinese version of the DSS was ...validated using a sample of 721 Chinese college students, 321 males and 400 females (KMO = 0.923; Bartlett = 5,058.492, p < .001). Confirmatory factor analysis (CFA) and item response theory (IRT) revealed that the five-factor model fits our data best. And the good criterion validity was shown through the association of the Chinese version of the DSS with anxiety and depression. The results of measurement invariance supported that the scale has measurement equivalence across the region (rural or urban). However, they did not support strict measurement invariance across gender. Overall, our results suggest that the DSS is an ideal tool for measuring digital stress in a Chinese sample. People can benefit from assessing digital stress, which has the potential to moderate the relationship between social media use and mental health. These psychometric investigations of the DSS will allow future research to investigate construct validity better.
Plain language summary Purpose: We aimed to assess the Psychometric Properties of the Chinese version of the Digital Stress Scale (DSS) among adolescents. Methods: First, we finished the Chinese version of the Digital Stress Scale by back-translation procedure and pre-test. Second, the internal consistency, criterion-related validity, construct validity, measurement equivalence and item analysis of the scales were tested. Conclusions: The DSS is a great instrument for measuring digital stress in a Chinese sample. Confirmatory factor analysis (CFA) and item response theory (IRT) revealed that the five-factor model fits our data well. The results of measurement invariance supported that the scale has measurement equivalence across the region (rural or urban). However, the scale did not show strict measurement invariance across gender. The criterion-related validity and internal consistency were great. Implications: People can benefit from assessing digital stress, which has the potential to moderate the relationship between social media use and mental health. Limitations: First, this study does not provide specific suggestions for future item modifications. Second, research samples are not conducive to the generalization of our findings. Third, this research does not use measures to answer a substantive developmental question using additional variables.
The violaxanthin (V)–antheraxanthin (A)–zeaxanthin (Z) (VAZ) cycle was deemed a non-second-scale process of photoprotection in higher plants and microalgae, but the validity of this view has not been ...confirmed. To test this view, we explored responses of the VAZ cycle and the relationship between the VAZ cycle and non-photochemical quenching (NPQ) under highlight at second and minute scales in
Heterosigma akashiwo
and
Platymonas
sp. Both A and Z were generated in
H. akashiwo
during 15 s of light exposure, whereas only A rapidly accumulated within 15 s of exposure in
Platymonas
sp. The above results, together with a time-dependent sigmoidal relationship between the VAZ cycle (de-epoxidation state, A/Chl
a
, and Z/Chl
a
) and NPQ, proved that the VAZ cycle was a second-scale process related to NPQ. In addition, we found that not all NPQ was dependent on the VAZ cycle and suggested that NPQ model should be carefully modified due to the species-specific proportions of de-epoxidation-dependent NPQ.
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