14 research outputs found
Energy levels of gapped graphene quantum dots in external fields
We investigate the energy levels of fermions within a circular graphene
quantum dot (GQD) subjected to external magnetic and Aharonov-Bohm fields.
Solving the eigenvalue equation for two distinct regions allows us to determine
the eigenspinors for the valleys and . By establishing the
continuity of eigenspinors at the GQD interface, we derive an equation that
reveals the reliance of energy levels on external physical parameters. Our
observations suggest that the symmetry of energy levels hinges on the selected
physical parameters. We observe that at low magnetic fields, the energy levels
display degeneracy, which diminishes as the field strength increases,
coinciding with the convergence of energy levels toward the Landau levels. We
illustrate that the introduction of a magnetic flux into the GQD leads to the
creation of an energy gap, extending the trapping time of electrons without
perturbing the system. Conversely, the addition of gap energy widens the band
gap, disrupting the system's symmetry by introducing new energy levels.Comment: 9 pages, 7 figure
Klein tunneling through triple barrier in AB bilayer graphene
We investigate the transport properties of charge carriers in AB bilayer
graphene through a triple electrostatic barrier. We calculate the transmission
and reflection using the continuity conditions at the interfaces of the triple
barrier together with the transfer matrix method. First, we consider the case
where the energy is less than the interlayer coupling and show that,
at normal incidence, transmission is completely suppressed in the gap for a
large barrier width while it appears in the gap for a small barrier width. For
energies greater than , we show that in the absence of an interlayer
potential difference, transmission is less than that of a single barrier, but
in its presence, transmission in the gap region is suppressed, as opposed to a
double barrier. It is found that one, two, or three gaps can be created
depending on the number of interlayer potential differences applied. Resonance
in the transmission channel is observed that is not seen in the single
and double barrier cases. Finally, we compute the conductance and show that the
number of peaks is greater than the double barrier case.Comment: 8 pages, 7 figure