Electrons trapped in graphene magnetic quantum dots with mass term

TL;DR

This paper explores how introducing a mass term in graphene quantum dots under magnetic fields can extend electron trapping times by creating energy gaps, with implications for controlling electron confinement.

Contribution

It demonstrates that adding a mass term to the Hamiltonian prolongs quasi-bound state lifetimes and enhances electron trapping in graphene quantum dots.

Findings

Energy gap extends quasi-bound state lifetimes.

Significant scattering efficiency occurs when the gap closes to the incident energy.

Increased electron density enhances trapping time.

Abstract

Owing to the Klein tunneling phenomenon, the permanent confinement or localization of electrons within a graphene quantum dot is unattainable. Nonetheless, a constant magnetic field can transiently ensnare an electron within the quantum dot, giving rise to what are known as quasi-bound states characterized by finite lifetimes. To prolong the retention of electrons within the quantum dot, we introduce a mass term into the Hamiltonian, thereby inducing an energy gap. We resolve the Dirac equation to ascertain the eigenspinors, and by ensuring their continuity at the boundaries, we investigate the scattering behavior. Our findings indicate that the presence of an energy gap can extend the lifetimes of these quasi-bound states within the quantum dot. In particular, we demonstrate that even in the absence of a magnetic field, the scattering efficiency attains significant levels when the energy gap gets closed to the incident energy of an electron traversing the quantum dot. It is found that an augmentation in the electron density within the quantum dot results in an enhancement of the electron-trapping time.