Transition metal dichalcogenides are layered materials which are composed of transition metals and chalcogens of the group VIA in a 1:2 ratio. These layered materials have been extensively investigated over synthesis and optical and electrical properties for several decades. It can be insulators, semiconductors, or metals revealing all types of condensed matter properties from a magnetic lattice distorted to superconducting characteristics. Some of these also feature the topological manner. Instead of covering the semiconducting properties of transition metal dichalcogenides, which have been extensively revisited and reviewed elsewhere, here we present the structures of metallic transition metal dichalcogenides and their synthetic approaches for not only high-quality wafer-scale samples using conventional methods (e.g., chemical vapor transport, chemical vapor deposition) but also local small areas by a modification of the materials using Li intercalation, electron beam irradiation, light illumination, pr...

van der Waals Metallic Transition Metal Dichalcogenides

Phase diagram and some physical properties of V2O3+x∗ (0 ⩽ x ⩽ 0.080)

Proceses in which electrons move by hopping from a full to an empty localized site in a degenerate electron gas are considered. One example is impurity conduction in doped and compensated silicon (e.g. Si:P). For the conductivity a variation as A exp (−B/T1/4) was predicted some years ago if the “interatomic” Coulomb interaction between electrons on different sites is neglected. If it is not neglected, a “Coulomb gap” EC of order e2/κa or in some cases less is introduced, where a is the distance between centres, as first pointed out in 1970 by Pollak. The activation energy by single-electron hops cannot be less than EC, so only if kT≫EC should they lead to the T1/4 law. Following earlier work (Mott 1976), it is shown that many-electron hops may lead to this law at low temperatures, with the same value of B but a smaller and T-dependent value of A. Somewhat different conclusions presented by Knotek and Pollak and others due to Efros and Shklovskii are discussed. Particular attention is given to the thermopower S, predicted to behave as T1/2 dlnN(E)/dE for hopping conduction both of single electron or (probably) of many-electron types; a new suggestion is an intermediate range of T where kT≅EC in which S=(k/e) (EC/2kT).

Hopping conduction and the Coulomb gap; applications to Fe 3 O 4 , Ti 4 O 7 and impurity conduction in Si:P

Structural chemistry of magnéli phases TinO2n−1 (4 ≤ n ≤ 9): IV. Superstructure in Ti4O7 at 140 K

Magnetic correlations in all four phases of pure and doped vanadium sesquioxide (V_2O_3) have been examined by magnetic thermal-neutron scattering. Specifically, we have studied the antiferromagnetic and paramagnetic phases of metallic V_(2-y)O_3, the antiferromagnetic insulating and paramagnetic metallic phases of stoichiometric V_2O_3, and the antiferromagnetic and paramagnetic phases of insulating V_(1.944)Cr_(0.056)O_3. While the antiferromagnetic insulator can be accounted for by a localized Heisenberg spin model, the long-range order in the antiferromagnetic metal is an incommensurate spin-density wave, resulting from a Fermi surface nesting instability. Spin dynamics in the strongly correlated metal are dominated by spin fluctuations with a "single lobe'' spectrum in the Stoner electron-hole continuum. Furthermore, our results in metallic V_2O_3 represent an unprecedentedly complete characterization of the spin fluctuations near a metallic quantum critical point, and provide quantitative support for the self-consistent renormalization theory for itinerant antiferromagnets in the small moment limit. Dynamic magnetic correlations for ħω<k_BT in the paramagnetic insulator carry substantial magnetic spectral weight. However, they are extremely short-ranged, extending only to the nearest neighbors. The phase transition to the antiferromagnetic insulator, from the paramagnetic metal and the paramagnetic insulator, introduces a sudden switching of magnetic correlations to a different spatial periodicity which indicates a sudden change in the underlying spin Hamiltonian. To describe this phase transition and also the unusual short-range order in the paramagnetic state, it seems necessary to take into account the orbital degrees of freedom associated with the degenerate d orbitals at the Fermi level in V_2O_3.

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Magnetic correlations and quantum criticality in the insulating antiferromagnetic, insulating spin liquid, renormalized Fermi liquid, and metallic antiferromagnetic phases of the Mott system V2O3

C. Schlenker

Papers

A new semiconducting ferrimagnet: A silicon manganese telluride

From the spin glass to the antiferromagnetic regime in (Ti1-xVx)2O3

Magnetic properties of vanadium-doped titanium diselenide

Metal-insulator transitions in (Ti1-xVx)4O7

Magnetic susceptibility and EPR of europium compounds: EuGa2S4, EuGa2Se4 and EuAl2S4