arXiv subjects

M. Sahakyan

Publications and source records attributed to M. Sahakyan.

3 recordsLinked to original sources

arXiv2025

Coexistence of superconductivity and excitonic pairing in a doped-biased double-layer system

The subject of the present study is the double-layer square-lattice system with the intralayer phonon modulations. We investigate the superconducting and excitonic pairings, as well as their coexistence, as functions of various physical parameters in the system. These parameters include temperature, intralayer and interlayer Coulomb interactions, the electron-phonon coupling parameter, doping and the applied electric field. The existence of superconductivity is demonstrated by considering the influence of intralayer phonons on the total charge density leading to the modification of the total energy of the electrons. Our results provides insights into the long-standing problem of the mechanism of superconductivity in high-$T_c$ cuprate superconductors.

cond-mat.str-el↗

arXiv2025

Unusual spin-triplet superconductivity in monolayer graphene

In this paper we consider the phonons in monolayer graphene and we show the possibility for the spin-triplet superconducting excitations states by discretizing the single-particle excitations near Fermi wave vector. The molonayer graphene was supposed to be exposed under the influence of the external gate-potential and the local Coulomb interaction effects have been taken into account at each lattice site position in the monolayer. A sufficiently large temperature domain was found, where the superconducting order parameter is not vanishing. Corresponding to this, at the surprisingly high temperature limit, we obtain a narrow domain of the electron-phonon coupling parameter $\lambda_{\rm eff}$, emphasizing the superconducting state. We discuss the localizing role of Hubbard-$U$ interaction and the effects external gate potential on the calculated physical parameters in the system. We explain the importance of the chemical potential in the formation of the superconducting state. We show the existence of a large superconducting band-gap in the system even in the case of the absence of the applied electric field potential.

cond-mat.str-el↗

arXiv2021

Dirac's spectrum from Newton laws in graphene

In the present work, we give a phenomenological theory of the monolayer graphene where two worlds quantum and classical meet together and complete each other in the most natural way. It appears that the graphene is the unique material where this complementarity could be explained in an effective way due to its exceptional band structure properties. We introduce the electron mass-vortex representation and we define surface tension excitation states in the monolayer graphene. By abstracting from the usual band energy dispersion we calculate the band mass of the electrons at the Dirac point by introducing the mathematical mass-dispersion relation. As a result, we obtain the Dirac energy dispersion in monolayer graphene from the classical Newton law. Within the semiclassical theory, we show the presence of the surface spin tension vectorial field which, possibly, closely relates the surface tension and spin tension states on the helical surface. We calculate the surface tension related with the electron band mass-vortex formation at the Dirac's point and we predict accurately the surface tension value related to the excitonic binding at the Dirac point as being formed from the electron and hole band mass-vortices. Moreover, we give the solution to a long-standing problem in the spin group theory and we construct an example which shows, phenomenologically, that the manifolds on $\rm S^{(6)}$ are not integrable. The principal reason for this is attributed to the irreducibility of the spinorial group $\rm Spin(6)^{\rm R}$ at the Dirac's point, due to the band mass formation via gravitational field.

cond-mat.mes-hall↗