Hofstadter-like spectrum and Magnetization of Artificial Graphene constructed with cylindrical and elliptical quantum dots

TL;DR

This study investigates how the shape of quantum dots in artificial graphene affects its electronic, magnetic, and topological properties, revealing shape-induced modifications in Hofstadter spectra and magnetization oscillations.

Contribution

It introduces a comparative analysis of circular and elliptical quantum dots in artificial graphene, highlighting shape-induced topological and spectral changes.

Findings

Ellipticity causes a topological change in miniband structure.

Elliptical dots open a gap and modify Hofstadter spectra.

Magnetization exhibits significant oscillations with magnetic flux.

Abstract

In this paper a comparative study of the electronic and magnetic properties of quasi-two-dimensional electrons in an artificial graphene-like superlattice composed of circular and elliptical quantum dots is presented. A complete orthonormal set of basis wave functions, which has previously been constructed in the frame of the Coulomb gauge for the vector potential has been implemented for calculation of the energy dispersions, the Hofstadter spectra, the density of states and the orbital magnetization of the considered systems, taking into account both the translational symmetry of the superlattice and the wave function phase-shifts due to the presence of a transverse external magnetic field. Our calculations indicate a topological change in the miniband structure due to the ellipticity of the quantum dots, and non-trivial modifications of the electron energy dispersion surfaces in reciprocal space with the change of the number of magnetic flux quanta through the unit cell of the superlattice. The ellipticity of the QDs leads to an opening of a gap and considerable modifications of the Hofstadter spectrum. The orbital magnetization is shown to reveal significant oscillations with the change of the magnetic flux. The deviation from the circular geometry of quantum dots has a qualitative impact on the dependencies of the magnetization on both the magnetic flux and the temperature.