Pontos quânticos em bicamada de grafeno rotacionada na presença de junções p-n

Abstract

Since the first experimental isolation of graphene in 2004, a vast number of research studies on this material have been conducted owing to its exotic physical properties, which are mostly due to its linear dispersion relation near the Fermi level. An additional degree of freedom to tune the electronic properties of graphene-based systems is provided by the stacking order, achieved by considering the overlaying and coupling of its monolayer compounds with offsets or rotations. In a bilayer system with the rotation of one of the graphene layers, figures known as Moiré patterns appear: quasi-periodic structures that, for certain magic angles, become periodic, forming Moiré superlattices. When the twist angle is close to the magic angle, the band structure of bilayer graphene near the Fermi energy becomes flat, leading to an unconventional superconductor-like behavior. Within the context of doped bilayer graphene-based systems and in addition to optoelectronic devices, it is natural to study junctions formed by excess or lack of electrons, that is, p-n junctions that can be generated by doping or application of external potentials, being such junctions a key piece for semiconductor devices, such as the diode. Thus, in this work, we theoretically investigate, using the tight-binding approach, the behavior of electrons and holes in circular twisted bilayer graphene quantum dots for potential applications in p-n junction formation. The quantum dots are defined by an infinite-mass potential, so the specific edge effects are absent. The effects of (i) the twisting angle, (ii) the p-n junction alignment, and (iii) the applied magnetic field perpendicular to the QD surface on the energy levels and on the spatial distribution of the confined states are studied.