The Abraham-Lorentz force and the time evolution of a chaotic system: The case of charged classical and quantum Duffing oscillators.

This paper proves that the Abraham-Lorentz (AL) force can noticeably modify the trajectories of the charged Duffing oscillators over time. The influence of the reaction force on the oscillator evolution is strongly enhanced if the system is considered at the level of quantum mechanics. For example, the AL force examined within the scope of Newtonian description can change the trajectory of the Duffing oscillator only if it has the mass of an electron.

Mixedness, Coherence and Entanglement in a Family of Three-Qubit States.

We consider a family of states describing three-qubit systems. We derived formulas showing the relations between linear entropy and measures of coherence such as degree of coherence, first- and second-order correlation functions. We show that qubit-qubit states are strongly entangled when linear entropy reaches some range of values.

New superconducting superhydride LaCH at relatively low stabilization pressure.

Motivated by the recent experimental discovery of high-temperature carbonaceous sulfur hydride (C-S-H), we have systematically explored the superconductivity of a carbonaceous lanthanum hydride (C-La-H) ternary compound in the pressure range of 50-250 GPa. Based on first-principles calculations and strong-coupling Migdal-Eliashberg theory, we find that a hitherto unreported LaCH ternary system is dynamically and thermally stable above 70 GPa in a clathrate structure with space group 3̄ and exhibits a superconducting critical temperature, , in the range of 69-140 K.

Stability and superconductivity of Ca-intercalated bilayer blue phosphorene.

Superconductivity attracts much attention in two-dimensional (2D) compounds due to their potential application in nano-superconducting devices. Inspired by a recent experiment reporting the superconducting state in twisted bilayer graphene, here, based on the first-principles density-functional theory complemented by the Eliashberg formalism, we have verified the stability and predicted superconductivity in Ca-intercalated bilayer blue phosphorene. The electron and phonon properties and electron-phonon coupling show that AA- and AA'-stacking orders of the phosphorene bilayer are dynamically stable and exhibit conventional phonon-mediated superconductivity with superconducting transition temperatures (Tc) of 11.

Nonadiabatic superconductivity in a Li-intercalated hexagonal boron nitride bilayer.

When considering a Li-intercalated hexagonal boron nitride bilayer (Li-hBN), the vertex corrections of electron-phonon interaction cannot be omitted. This is evidenced by the very high value of the ratio λω/ε ≈ 0.46, where λ is the electron-phonon coupling constant, ω is the Debye frequency, and ε represents the Fermi energy.

Superconductivity in bilayer graphene intercalated with alkali and alkaline earth metals.

With the enormous research activity focused on graphene in recent years, it is not surprising that graphene superconductivity has become an attractive area of research. To date, no superconducting properties have been experimentally observed in the pristine form of graphene but controllable structure manipulation is a promising way to induce a superconducting state in graphene-based systems. Therefore, herein we investigate the possible superconductivity in two-layer graphene intercalated with atoms of alkali and alkaline earth metals.

Structural, electronic, vibrational, and superconducting properties of hydrogenated chlorine.

Recent measurements have set a new record for the superconducting transition temperature ( ) at which a material losses electrical resistivity and exhibits ideal diamagnetism. Theory-oriented experiments show that the compressed hydride of Group VI (hydrogen sulfide, HS) exhibits a superconducting state at 203 K. Moreover, a Group V hydride (phosphorus hydride, PH) has also been studied and its reached a maximum of 103 K.

Anomalously high value of Coulomb pseudopotential for the HS superconductor.

The HS and HS compounds are the two candidates for the low-temperature phase of compressed sulfur-hydrogen system. We have shown that the value of Coulomb pseudopotential (μ*) for HS ([T] = 36 K and p = 112 GPa) is anomalously high. The numerical results give the limitation from below to μ* that is equal to 0.

Unusual sulfur isotope effect and extremely high critical temperature in HS superconductor.

Recent experiments have set a new record for the transition temperature at which a material (hydrogen sulfide, HS) becomes superconducting. Moreover, a pronounced isotope shift of T in DS is evidence of an existence of phonon-mediated pairing mechanism of superconductivity that is consistent with the well established Bardeen-Cooper-Schrieffer scenario. Herein, we reported a theoretical studies of the influence of the substitution of S atoms by the heavier isotopes S, S and S on the electronic properties, lattice dynamics and superconducting critical temperature of HS.

First-principles study of superconducting hydrogen sulfide at pressure up to 500 GPa.

We investigate the possibility of achieving the room-temperature superconductivity in hydrogen sulfide (HS) through increasing external pressure, a path previously widely used to reach metallization and superconducting state in novel hydrogen-rich materials. The electronic properties and superconductivity of HS in the pressure range of 250-500 GPa are determined by the first-principles calculations. The metallic character of a body-centered cubic Im[Formula: see text]m structure is found over the whole studied pressure.

Quantum conductance of silicon-doped carbon wire nanojunctions.

Unknown quantum electronic conductance across nanojunctions made of silicon-doped carbon wires between carbon leads is investigated. This is done by an appropriate generalization of the phase field matching theory for the multi-scattering processes of electronic excitations at the nanojunction and the use of the tight-binding method. Our calculations of the electronic band structures for carbon, silicon, and diatomic silicon carbide are matched with the available corresponding density functional theory results to optimize the required tight-binding parameters.

Pairing mechanism for the high-TC superconductivity: symmetries and thermodynamic properties.

The pairing mechanism for the high-Tc superconductors based on the electron-phonon (EPH) and electron-electron-phonon (EEPH) interactions has been presented. On the fold mean-field level, it has been proven, that the obtained s-wave model supplements the predictions based on the BCS van Hove scenario. In particular: (i) For strong EEPH coupling and T < T(C) the energy gap (Δtot) is very weak temperature dependent; up to the critical temperature Δtot extends into the anomalous normal state to the Nernst temperature.