How the interacting electronic states and phases of layered transition-metal dichalcogenides evolve when thinned to the single-layer limit is a key open question in the study of two-dimensional ...materials. Here, we use angle-resolved photoemission to investigate the electronic structure of monolayer VSe
grown on bilayer graphene/SiC. While the global electronic structure is similar to that of bulk VSe
, we show that, for the monolayer, pronounced energy gaps develop over the entire Fermi surface with decreasing temperature below T
= 140 ± 5 K, concomitant with the emergence of charge-order superstructures evident in low-energy electron diffraction. These observations point to a charge-density wave instability in the monolayer that is strongly enhanced over that of the bulk. Moreover, our measurements of both the electronic structure and of X-ray magnetic circular dichroism reveal no signatures of a ferromagnetic ordering, in contrast to the results of a recent experimental study as well as expectations from density functional theory. Our study thus points to a delicate balance that can be realized between competing interacting states and phases in monolayer transition-metal dichalcogenides.
The list of interesting electrical properties exhibited by transition metal
dichalcogenides has grown with the discovery of extremely large
magnetoresistance (MR) and type-II Weyl semimetal behaviour ...in WTe$_2$ and
MoTe$_2$. The extremely large MR in WTe$_2$ is still not adequately understood.
Here, we systematically study the effect of Mo substitution on the quantum
oscillations in the MR in WTe$_2$. The MR decreases with Mo substitution,
however, the carrier concentrations extracted from the quantum oscillations
show that the charge compensation improves. We believe that earlier
interpretations based on the two-band theory, which attribute the decrease in
MR to charge imbalance, could be incorrect due to over-parametrization. We
attribute the decrease in MR in the presence of charge compensation to a fall
in transport mobility, which is evident from the residual resistivity ratio
data. The quantum scattering time and the effective masses do not change within
experimental errors upon substitution.
The list of interesting electrical properties exhibited by transition metal dichalcogenides has grown with the discovery of extremely large magnetoresistance (MR) and type-II Weyl semimetal behaviour ...in WTe\(_2\) and MoTe\(_2\). The extremely large MR in WTe\(_2\) is still not adequately understood. Here, we systematically study the effect of Mo substitution on the quantum oscillations in the MR in WTe\(_2\). The MR decreases with Mo substitution, however, the carrier concentrations extracted from the quantum oscillations show that the charge compensation improves. We believe that earlier interpretations based on the two-band theory, which attribute the decrease in MR to charge imbalance, could be incorrect due to over-parametrization. We attribute the decrease in MR in the presence of charge compensation to a fall in transport mobility, which is evident from the residual resistivity ratio data. The quantum scattering time and the effective masses do not change within experimental errors upon substitution.
Layered transition-metal dichalcogenides are proposed as building blocks for van der Waals (vdW) heterostructures due to their graphene-like two dimensional structure. For this purpose, a magnetic ...semiconductor could represent an invaluable component for various spintronics and topotronics devices. Here, we combine different local magnetic probe spectroscopies with angle-resolved photoemission and density-functional theory calculations to show that 2H-MoTe2 is on the verge of becoming magnetic. Our results present clear evidence that the magnetism can be "switched on" by a hydrogen-like impurity. We also show that this magnetic state survives up to the free surface region, demonstrating the material's potential applicability as a magnetic component for thin-film heterostructures.
VSe2 is a transition metal dichaclogenide which has a charge-density wave transition that has been well studied. We report on a low-temperature upturn in the resistivity and, at temperatures below ...this resistivity minimum, an unusual magnetoresistance which is negative at low fields and positive at higher fields, in single crystals of VSe2. The negative magnetoresistance has a parabolic dependence on the magnetic field and shows little angular dependence. The magnetoresistance at temperatures above the resistivity minimum is always positive. We interpret these results as signatures of the Kondo effect in VSe2. An upturn in the susceptibility indicates the presence of interlayer V ions which can provide the localized magnetic moments required for scattering the conduction electrons in the Kondo effect. The low-temperature behaviour of the heat capacity, including a high value of gamma, along with a deviation from a Curie-Weiss law observed in the low-temperature magnetic susceptibility, are consistent with the presence of magnetic interactions between the paramagnetic interlayer V ions and a Kondo screening of these V moments.
We performed angle dependent magnetoresistance study of a metallic single crystal sample of Bi2Te3. We find that the magnetoresistance is highly asymmetric in positive and negative magnetic fields ...for small angles between the magnetic field and the direction perpendicular to the plane of the sample. The magnetoresistance becomes symmetric as the angle approaches 90 degree. The quantum Shubnikov de-Haas oscillations are symmetric and show signatures of topological surface states with Dirac dispersion in the form of non-zero Berry phase. However, the angular dependence of these oscillations suggests a complex three dimensional Fermi surface as the source of these oscillations, which does not exactly conform with the six ellipsoidal model of the Fermi surface of Bi2Te3. We attribute the asymmetry in the magnetoresistance to a mixing of the Hall voltage in the longitudinal resistance due to the comparable magnitude of the Hall and longitudinal resistance in our samples. This provides a clue to understanding the asymmetric magnetoresistance often seen in this and similar materials. Moreover, the asymmetric nature evolves with exposure to atmosphere and thermal cycling, which we believe is either due to exposure to atmosphere or thermal cycling, or both affecting the carrier concentration and hence the Hall signal in these samples. However, the quantum oscillations seem to be robust against these factors which suggests that the two have different origins.
In this report, we scrutinize the thickness dependent resistivity data from the recent literature on electrical transport measurements in topological insulators. A linear increase in resistivity with ...increase in thickness is expected in the case of these materials since they have an insulating bulk and conducting surface. However, such a trend is not seen in the resistivity versus thickness data for all the cases examined, except for some samples, where it holds for a narrow range of thickness.
Bi2Te3 is a member of a new class of materials known as topological insulators which are supposed to be insulating in the bulk and conducting on the surface. However experimental verification of the ...surface states has been difficult in electrical transport measurements due to a conducting bulk. We report low temperature magnetotransport measurements on single crystal samples of Bi2Te3. We observe metallic character in our samples and large and linear magnetoresistance from 1.5 K to 290 K with prominent Shubnikov-de Haas (SdH) oscillations whose traces persist upto 20 K. Even though our samples are metallic we are able to obtain a Berry phase close to the value of {\pi} expected for Dirac fermions of the topological surface states. This indicates that we might have obtained evidence for the topological surface states in metallic single crystals of Bi2Te3. Other physical quantities obtained from the analysis of the SdH oscillations are also in close agreement with those reported for the topological surface states. The linear magnetoresistance observed in our sample, which is considered as a signature of the Dirac fermions of the surface states, lends further credence to the existence of topological surface states.
Environment management is gaining awareness among businesses worldwide to achieve sustainable development, and companies are under pressure to adopt green practices in their supply chain. This ...research aims to determine the green practices and develop a contextual interrelationships framework to explore the reason behind the lack of green supply chain management (GSCM). The study consist of qualitative and quantitative research methods. The research followed several rounds of discussion (Delphi method) with industry experts to determine and finalize the green practices in the petroleum industry. A novel modeling technique, a modified total interpretive structural model (TISM-P), explores the contextual relationship between the green practices. The research suggests that green information systems are an independent practice that drives the other practices (green procurement, green production, green distribution, and investment recovery). The study also describes practices internal environment management and co-operation with customers have high driving and high dependence power. The study is also novel in identifying the green practices in the petroleum industry.
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•Research aim is to determine the green practices in petroleum industry.•Study developed a contextual interrelationship of green practices.•Total Interpretive Structural Modeling-Polarity is proposed in the study.•MICMAC analysis is performed to classify the green practices.•Results reveal green information system is the heart of GSCM.
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