The consequences of the Jahn-Teller (JT) orbital-lattice coupling for magnetism of pseudospin J_{eff}=1/2 and J_{eff}=0 compounds are addressed. In the former case, represented by Sr_{2}IrO_{4}, this ...coupling generates, through the so-called pseudo-JT effect, orthorhombic deformations of a crystal concomitant with magnetic ordering. The orthorhombicity axis is tied to the magnetization and rotates with it under magnetic field. The theory resolves a number of puzzles in Sr_{2}IrO_{4} such as the origin of in-plane magnetic anisotropy and magnon gaps, metamagnetic transition, etc. In J_{eff}=0 systems, the pseudo-JT effect leads to spin-nematic transition well above magnetic ordering, which may explain the origin of "orbital order" in Ca_{2}RuO_{4}.
Tungsten ditelluride has attracted intense research interest due to the recent discovery of its large unsaturated magnetoresistance up to 60 T. Motivated by the presence of a small, sensitive Fermi ...surface of 5d electronic orbitals, we boost the electronic properties by applying a high pressure, and introduce superconductivity successfully. Superconductivity sharply appears at a pressure of 2.5 GPa, rapidly reaching a maximum critical temperature (Tc) of 7 K at around 16.8 GPa, followed by a monotonic decrease in Tc with increasing pressure, thereby exhibiting the typical dome-shaped superconducting phase. From theoretical calculations, we interpret the low-pressure region of the superconducting dome to an enrichment of the density of states at the Fermi level and attribute the high-pressure decrease in Tc to possible structural instability. Thus, tungsten ditelluride may provide a new platform for our understanding of superconductivity phenomena in transition metal dichalcogenides.
Abstract
The progress in exploiting new electronic materials has been a major driving force in solid-state physics. As a new state of matter, a Weyl semimetal (WSM), in particular a type-II WSM, ...hosts Weyl fermions as emergent quasiparticles and may harbour novel electrical transport properties. Nevertheless, such a type-II WSM material has not been experimentally observed. In this work, by performing systematic magneto-transport studies on thin films of a predicted material candidate WTe
2
, we observe notable negative longitudinal magnetoresistance, which can be attributed to the chiral anomaly in WSM. This phenomenon also exhibits strong planar orientation dependence with the absence along the tungsten chains, consistent with the distinctive feature of a type-II WSM. By applying a gate voltage, we demonstrate that the Fermi energy can be
in-situ
tuned through the Weyl points via the electric field effect. Our results may open opportunities for implementing new electronic applications, such as field-effect chiral devices.
Semiconducting two-dimensional transition metal dichalcogenides are emerging as top candidates for post-silicon electronics. While most of them exhibit isotropic behaviour, lowering the lattice ...symmetry could induce anisotropic properties, which are both scientifically interesting and potentially useful. Here we present atomically thin rhenium disulfide (ReS2) flakes with unique distorted 1T structure, which exhibit in-plane anisotropic properties. We fabricated monolayer and few-layer ReS2 field-effect transistors, which exhibit competitive performance with large current on/off ratios (∼10(7)) and low subthreshold swings (100 mV per decade). The observed anisotropic ratio along two principle axes reaches 3.1, which is the highest among all known two-dimensional semiconducting materials. Furthermore, we successfully demonstrated an integrated digital inverter with good performance by utilizing two ReS2 anisotropic field-effect transistors, suggesting the promising implementation of large-scale two-dimensional logic circuits. Our results underscore the unique properties of two-dimensional semiconducting materials with low crystal symmetry for future electronic applications.
A nanohybrid probe was fabricated from manganese dioxide nanosheets (MnO
2
NSs), molybdenum disulfide quantum dots (MoS
2
QDs) and o-phenylenediamine (OPD) for ratiometric detection of glutathione ...(GSH) in aqueous solutions and living cells. The MoS
2
QDs act as the fluorescent “turn off-on” units. The MnO
2
NSs have 3 functions, viz. (a) as fluorescence quencher, (b) as fluorescence initiator for oxidized OPD (ox OPD) and (c) as selective recognizer of GSH. The quenched blue fluorescence of the MoS
2
QDs can be restored by introducing GSH that reduces the MnO
2
NSs. However, the green fluorescence of ox OPD is decreased through the loss of peroxidase activity of MnO
2
NSs in the presence of GSH. Therefore, the ratio of the fluorescence intensities at 560 and 400 nm (from ox OPD and MoS
2
QDs, respectively) linearly decreases with increasing concentrations of GSH. Under the optimal conditions, the detection limit for GSH is as low as 90 nM. The method was successfully applied to the determination of GSH in human serum samples. This nanohybrid also is shown to be membrane-permeable and to have low cytotoxicity. This paved the way to intracellular sensing of GSH in living normal HFF and cancerous HeLa cells. Additionally, by combining with logic gate, this assay was successfully applied to visually discriminate changes in the intracellular GSH. The combination of ratiometric fluorometry and peroxidase mimicking can provide a wide range of application in bioanalysis and intracellular imaging.
Graphical abstract
Schematic representation of the ratiometric fluorometric detection and cellular imaging of glutathione using a nanohybrid composed of MoS
2
quantum dots and MnO
2
nanosheets with dual (blue and green emission and peroxidase mimicking properties.
This study, using databases from the AsiaBarometer Surveys 2006 and 2007, empirically investigates whether and how English proficiency and happiness are linked in 14 East and Southeast Asian ...countries or regions. Based on the large-scale dataset of 14,811 respondents, we conducted hierarchical regression analyses and found that: (i) English proficiency is positively associated with happiness; (ii) the focal relationship is partly mediated by income and leisure satisfaction; and (iii) the focal relationship is negatively moderated by the national economy. These findings show the instrumentality of English learning in a globalized world and enrich our understanding about the influence factors of happiness, and contribute to the literature on English proficiency and happiness as well.
Two dimensional materials have many outstanding intrinsic advantages that can be utilized to enhance the photocatalytic efficiency of water splitting. Herein, based on ab initio calculations, we ...reveal that for monolayer and multilayer rhenium disulphide (ReS2), the band gap and band edge positions are an excellent match with the water splitting energy levels. Moreover, the effective masses of the carriers are relatively light, and the optical absorption coefficients are high under visible illumination. Due to the feature of weak interlayer coupling, these properties are independent of the layer thickness. Our results suggest that ReS2 is a stable and efficient photocatalyst with potential applications in the use of solar energy for water splitting.
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