The entanglement of charge density wave (CDW), superconductivity, and topologically nontrivial electronic structure has recently been discovered in the kagome metal $A{\mathrm{V}}_3{\mathrm{Sb}}_5$ ($A=\mathrm{K}$, Rb, Cs) family. With high-resolution angle-resolved photoemission spectroscopy, we study the electronic properties of CDW and superconductivity in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$. The spectra around $\overline{K}$ is found to exhibit a peak-dip-hump structure associated with two separate branches of dispersion, demonstrating the isotropic CDW gap opening below $E_F$. The peak-dip-hump line shape is contributed by linearly dispersive Dirac bands in the lower branch and a dispersionless flat band close to $E_F$ in the upper branch. The electronic instability via Fermi surface nesting could play a role in determining these CDW-related features. The superconducting gap of $\sim 0.4\mathrm{meV}$ is observed on both the electron band around $\overline{\mathrm{\Gamma }}$ and the flat band around $\overline{K}$, implying the multiband superconductivity. The finite density of states at $E_F$ in the CDW phase is most likely in favor of the emergence of multiband superconductivity, particularly the enhanced density of states associated with the flat band. Our results not only shed light on the controversial origin of the CDW, but also offer insights into the relationship between CDW and superconductivity.

The structure of a new non-carbon (beryllium oxide BeO) nanotube consisting of a rolled-up graphene sheet is proposed, and its physical properties are described. Ab initiocalculations of the binding...

The structures and electron properties of new superlattices formed on graphene by adsorbed hydrogen molecules are theoretically described. It has been shown that superlattices of the (n, 0) zigzag type with linearly arranged pairs of H atoms have band structures similar to the spectra of (n, 0) carbon nanotubes. At the same time, superlattices of the (n, n) type with a “staircase” of adsorbed pairs of H atoms are substantially metallic with a high density of electronic states at the Fermi level and this property distinguishes their spectra from the spectra of the corresponding (n, n) nanotubes. The features of the spectra have the Van Hove form, which is characteristic of each individual superlattice. The possibility of using such planar structures with nanometer thickness is discussed.

The absorption energy and diffusion rates of lithium atoms inside graphitelike boron carbide (BC3) crystal are investigated by the ab initio pseudopotential density-functional method using generalized gradient approximation. It is shown that lithium may effectively intercalate this structure with the maximum lithium concentration corresponding to Li2BC3 stoichiometry, which is threefold in comparison to lithium in graphite. The potential barrier values for lithium diffusion both at low and maximum concentration are about 0.19 eV, so lithium atoms inside the BC3 structure can move easily. These findings suggest that boron carbide looks like a good candidate as an anode material in lithium ion batteries.

A possibility of using some kinetic models for the description of detonation of a gaseous hydrogen–air mixture is justified. A hierarchy of mathematical models from the simplest model of combustion under static conditions to the model of unsteady nonequilibrium gas dynamics is numerically constructed. Verification is performed on the basis of experimental data on the ignition delay time as a function of temperature and on the detonation wave velocity as a function of dilution of the mixture by argon or nitrogen. A mathematical technology for the description of cellular detonation propagation in channels of various engineering devices is developed on the basis of detailed and reduced kinetic mechanisms of nonequilibrium chemical transformations within the framework of the ANSYS Fluent commercial software system. It is demonstrated that the cell size in a mixture diluted by argon by 92% in a channel 30 mm wide is in good agreement with experimental data.