arXiv subjects

Armen Harutyunyan

Publications and source records attributed to Armen Harutyunyan.

3 recordsLinked to original sources

arXiv2026

Rashba-Cavity Engineering of Energy Gaps and Spin-Hall Conductivity in Semiconducting Artificial Graphene

We investigate the combined effect of a far - infrared cavity field and Rashba spin - orbit interaction on the band structure and transport properties of artificial graphene composed of quasi-2D InAs/GaAs quantum dots. The coupling to cavity photons is modeled by constructing a complete basis as the tensor product of the electronic Hilbert space and the Fock space. Our numerical calculations for the system embedded in a linear cavity predict the existence of both type-I and type-II Dirac points which can be distinguished by their response to Rashba interaction. Namely, Rashba coupling opens a gap at type-II Dirac points, while type-I Dirac points remain gapless. The possibility of gap-opening for type-II Dirac points is demonstrated analytically as well. For both cylindrical and linear cavities, we demonstrate the formation of electron - photon hybrid states and Rabi splittings between energy minibands. Multiple crossings, and anticrossings between Dirac-band replicas produce pronounced modifications of the spin-Hall conductivity, including strong anisotropy and oscillatory behavior controlled by cavity geometry and polarization of photons. Our results show that the interplay between Rashba and cavity couplings governs Dirac-point physics and provides a route toward tunable polaritonic spin-transport in engineered nanostructures.

cond-mat.mes-hall↗

arXiv2025

Quantum Interference and Rashba Spin-Orbit Coupling in a Chain of Planar Quantum Rings: Effects on Magnetic and Transport Properties

Magneto-transport properties of a two-dimensional electron gas in a chain of planar quantum rings are investigated under the Rashba spin-orbit interaction and a transverse homogeneous magnetic field. A modulation potential function models the ring-chain periodicity along one direction and the confinement in the perpendicular one. The electron energy minibands collapse into discrete levels with high degeneracy at specific magnetic field values. The Rashba effect significantly influences the system's properties. Calculations reveal a transition from diamagnetic to paramagnetic behavior in the spin-difference orbital magnetization at high Rashba coupling strengths. This is consistent with the reversal of the spin-difference persistent current observed at the same Rashba values. Total and spin-difference magnetizations exhibit oscillations linked to miniband nodes. The longitudinal magnetoconductance component shows oscillations resembling Shubnikov-De Haas behavior, while the transverse component displays a ladder-like profile reminiscent of the quantum Hall effect. However, both phenomena are more closely associated with the periodic collapse of minibands, leading to strong density-of-states oscillations, rather than with the mechanisms behind the quantum Hall effect. This highlights the rich physics of quantum topological phases in nanostructures with non-trivial geometry. At high Rashba coupling, this behavior degrades. Spin magnetization shows pronounced oscillations, indicating complex interplay between the Zeeman and Rashba effects on spin polarization. These results offer insights into experimentally relevant electronic and spin characteristics attainable in modulated semiconductor structures, contributing to the development of advanced 2D-based materials for magneto-transport and spintronics applications.

cond-mat.mes-hall↗

arXiv2024

Magneto-optical properties of electron gas in a chain of planar quantum rings: Effect of screening on the signature of quantum phase interference

The equilibrium properties and interminiband transitions for Hartree-interacting two-dimensional electron gas in a one-dimensional chain of planar quantum rings subjected to a transverse homogeneous magnetic field are examined theoretically and numerically. The proposed analytical models for the external modulation potential and the basis wave-function reflect the symmetry and the topology of the system allowing to get high accuracy results in comparatively short computational times. The calculated dependencies of the electronic band structure versus magnetic field show two detached minibands in the region of low energies, while higher minibands manifest multiple crossings and anticrossings. The existence of highly degenerate energy levels (referred to as miniband nodes) for certain values of magnetic field is revealed. The miniband nodes are preserved when taking into account the Coulomb interaction of the electrons. The interaction leads to an up-shift and a broadening of the minibands, as well as to a shift of the nodes toward the larger values of the magnetic field. The miniband nodes have their signature in the magnetization of the electron gas and in the interminiband transitions. The number of electrons per a unite cell of the system has a strong impact on the current density distribution, magnetization and the oscillator strength. The obtained results open new opportunities for a flexible manipulation of magneto-optical properties of future devices operating in far-infrared and THz regimes.

cond-mat.mes-hall↗