Results 1 - 10 of 1323
Results 1 - 10 of 1323. Search took: 0.024 seconds
|Sort by: date | relevance|
[en] We have systematically investigated the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction between two magnetic impurities in Weyl semimetals with arbitrary monopole charge Q. We find that the RKKY interaction becomes intrinsically anisotropic for , and its dependence on Fermi energy and impurity separation is directly controlled by the monopole charge. With the increase of Q, the RKKY interaction becomes more long-ranged and more anisotropic, which makes interesting magnetic orders easier to form and thus may have important applications in spintronics. (paper)
[en] We report a comparative polarized Raman study of Weyl semimetals TaAs, NbAs, TaP and NbP. The evolution of the phonon frequencies with the sample composition allows us to determine experimentally which atoms are mainly involved for each vibration mode. Our results confirm previous first-principles calculations indicating that the A1, B1(2), E(2) and E(3) modes involve mainly the As(P) atoms, the B1(1) mode is mainly related to Ta(Nb) atoms, and the E(1) mode involves both kinds of atoms. By comparing the energy of the different modes, we establish that the B1(1), B1(2), E(2) and E(3) become harder with increasing chemical pressure. This behaviour differs from our observation on the A1 mode, which decreases in energy, in contrast to its behaviour under external pressure. (paper)
[en] To assess the risks that contaminated soils pose to the environment properly a greater understanding of how soil biota influence the mobility of metal(loid)s in soils is required. Lumbricus terrestris L. were incubated in three soils contaminated with As, Cu, Pb and Zn. The concentration and speciation of metal(loid)s in pore waters and the mobility and partitioning in casts were compared with earthworm-free soil. Generally the concentrations of water extractable metal(loid)s in earthworm casts were greater than in earthworm-free soil. The impact of the earthworms on concentration and speciation in pore waters was soil and metal specific and could be explained either by earthworm induced changes in soil pH or soluble organic carbon. The mobilisation of metal(loid)s in the environment by earthworm activity may allow for leaching or uptake into biota. - Research highlights: → Earthworms increase the mobility and availability of metals and metalloids in soils. → We incubated L. terrestris in three soils contaminated with As, Cu, Pb and Zn. → Earthworms increased the mobility of As, Cu, Pb and Zn in their casts. → The mechanisms for this could be explained by changes in pH or organic carbon. - Lumbricus terrestris change the partitioning of metal(loid)s between soil constituents and increase the mobility of metal(loid)s in casts and pore water.
[en] We discuss our recent optical investigation of , a representative type II Weyl semimetal, by considering a simple scheme for the electronic structure, which can be embedded within a recent theoretical approach for the calculation of the excitation spectrum. Our study allows us disentangling the generic optical fingerprints of Weyl fermions, which are in broad agreement with the theoretical predictions but also challenge the present understanding of their electrodynamic response.
[en] The 3D analogue of graphene is known as Weyl semimetal, where the excitations energy is a linear function of their momentum. Floquet theory is an alternative way of study of conventional Rabi oscillations in off-resonant case. In this article, the study of collapse-revival spectra of Weyl semimetal has been done and shown how anisotropy plays an essential role in such spectra. The importance of Floquet theory over rotating wave approximation has been described in case of low energy physics. There is a new type of shift in the resonance condition of Floquet theory, called Floquet-Bloch-Siegert shift contains anisotropic nature. A possibility of Floquet oscillations in zero photon limit, leads presence of Floquet oscillations in the vacuum. The anisotropic nature of Floquet oscillation has also been justified via using numerical method and machine learning approach. (paper)
[en] Synthetic approaches to tetrabenzotriazaporphyrins and their complexes with metals and semimetals (P, Si) are considered. Methods for complexation of free-base tetrabenzotriazaporphyrin ligands and the preparation of water-soluble derivatives via the introduction of a sulfo group are analyzed. Particular attention is given to investigations of this class of compounds by electronic absorption spectroscopy and possibilities of their practical application. The bibliography includes 80 references
[en] Highlights: • Achieved proper topological classification of time-reversal symmetric Weyl semimetals. • Dual classification is provided by history of Weyl point creation/annihilation. • Weyl points are identified as monopoles for Fu–Kane–Mele invariants. • Fermi arcs and Dirac cones are transmutable without a topological phase transition. • Interface between Weyl semimetals can host a generalised Dirac cone. - Abstract: In semimetals with time-reversal symmetry, the interplay between Weyl points and Fu–Kane–Mele indices results in coexisting surface Dirac cones and Fermi arcs that are transmutable without a topological phase transition. We show that Weyl points act as a new type of monopole, and that their connectivity is essential for capturing the full topology of semimetals and their role as intermediaries of topological insulator transitions. The history of Weyl point creation–annihilation provides a simple and mathematically equivalent way to classify semimetals, and directly prefigures the surface state topology. We further predict the possibility of a topological Dirac cone on the interface between two Weyl semimetals.
[en] Magneto-transport properties of insulating bulk states in Bi(111) films are systematically investigated under the parallel field (B_‖). We find that the magnetotransport of the B_‖ field is a more powerful tool to distinguish the bulk states and the surface states. A large magnetoresistance (MR) up to 20% in the B_‖ field is induced by the insulating bulk states for the suppression of the backward scattering. With the increasing thickness, a positive MR(B_‖) from magnetic induced boundary scattering appears in the semimetal films. As the thickness is reduced to 10 nm, the positive MR(B_‖) is induced by weak anti-localization from the surface states. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
[en] An axion insulator is a correlated topological phase, predicted to arise from the formation of a charge density wave in Weyl semimetals. The accompanying sliding mode in the charge density wave phase, the phason, is an axion. It is expected to cause anomalous magneto-electric transport effects. However, this axionic charge density wave has so far eluded experimental detection. In this paper, we report for the first time the observation of a large, positive contribution to the magneto-conductance in the sliding mode of the charge density wave Weyl semimetal (TaSe)I for collinear electric and magnetic fields (EB). The positive contribution to the magneto-conductance originates from the anomalous axionic contribution of the chiral anomaly to the phason current, and is locked to the parallel alignment of E and B. By rotating B, we show that the angular dependence of the magneto-conductance is consistent with the anomalous transport of an axionic charge density wave.
[en] The possibility of coexistence of ferromagnetic ordering and superconductivity in a two-band model of semimetal with an isotropic current-carrier spectrum is investigated in detail. It is shown that triplet electron-hole and Cooper pairing with weak electron coupling can coexist at unequal electron and hole densities. A nonzero mean magnetic moment appears in this case