Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userElectronic band gaps and transport properties in aperiodic bilayer graphene superlattices of Thue-Morse sequence
89
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We investigate electronic band structure and transport properties in bilayer graphene superlattices of Thue-Morse sequence. It is interesting to find that the zero-$bar{k}$ gap center is sensitive to interlayer coupling $t$, and the centers of all gaps shift versus $t$ at a linear way. Extra Dirac points may emerge at $k_{y} e$0, and when the extra Dirac points are generated in pairs, the electronic conductance obeys a diffusive law, and the Fano factor tends to be 1/3 as the order of Thue-Morse sequence increases. Our results provide a flexible and effective way to control the transport properties in graphene.
rate research
Read More
We investigate the electronic Bloch oscillation in bilayer graphene gradient superlattices using transfer matrix method. By introducing two kinds of gradient potentials of square barriers along electrons propagation direction, we find that Bloch oscillations up to terahertz can occur. Wannier-Stark ladders, as the counterpart of Bloch oscillation, are obtained as a series of equidistant transmission peaks, and the localization of the electronic wave function is also signature of Bloch oscillation. Forthermore, the period of Bloch oscillation decreases linearly with increasing gradient of barrier potentials.
We study, within the tight-binding approximation, the electronic properties of a graphene bilayer in the presence of an external electric field applied perpendicular to the system -- emph{biased bilayer}. The effect of the perpendicular electric field is included through a parallel plate capacitor model, with screening correction at the Hartree level. The full tight-binding description is compared with its 4-band and 2-band continuum approximations, and the 4-band model is shown to be always a suitable approximation for the conditions realized in experiments. The model is applied to real biased bilayer devices, either made out of SiC or exfoliated graphene, and good agreement with experimental results is found, indicating that the model is capturing the key ingredients, and that a finite gap is effectively being controlled externally. Analysis of experimental results regarding the electrical noise and cyclotron resonance further suggests that the model can be seen as a good starting point to understand the electronic properties of graphene bilayer. Also, we study the effect of electron-hole asymmetry terms, as the second-nearest-neighbor hopping energies $t$ (in-plane) and $gamma_{4}$ (inter-layer), and the on-site energy $Delta$.
The generalized tight-binding model is developed to investigate the magneto-electronic properties in twisted bilayer graphene system. All the interlayer and intralayer atomic interactions are included in the Moire superlattice. The twisted bilayer graphene system is a zero-gap semiconductor with double-degenerate Dirac-cone structures, and saddle-point energy dispersions appearing at low energies for cases of small twisting angles. There exist rich and unique magnetic quantization phenomena, in which many Landau-level subgroups are induced due to specific Moire zone folding through modulating the various stacking angles. The Landau-level spectrum shows hybridized characteristics associated with the those in monolayer, and AA $&$ AB stackings. The complex relations among the different sublattices on the same and different graphene layers are explored in detail.
Prompted by recent reports on $sqrt{3} times sqrt{3}$ graphene superlattices with intrinsic inter-valley interactions, we perform first-principles calculations to investigate the electronic properties of periodically nitrogen-doped graphene and carbon nanotube nanostructures. In these structures, nitrogen atoms substitute one-sixth of the carbon atoms in the pristine hexagonal lattices with exact periodicity to form perfect $sqrt{3} times sqrt{3}$ superlattices of graphene and carbon nanotubes. Multiple nanostructures of $sqrt{3} times sqrt{3}$ graphene ribbons and carbon nanotubes are explored, and all configurations show nonmagnetic and metallic behaviors. The transport properties of $sqrt{3} times sqrt{3}$ graphene and carbon nanotube superlattices are calculated utilizing the non-equilibrium Greens function formalism combined with density functional theory. The transmission spectrum through the pristine and $sqrt{3} times sqrt{3}$ armchair carbon nanotube heterostructure shows quantized behavior under certain circumstances.
We show that, with the exception of the words $a^2ba^2$ and $b^2ab^2$, all (finite or infinite) binary patterns in the Prouhet-Thue-Morse sequence can actually be found in that sequence as segments (up to exchange of letters in the infinite case). This result was previously attributed to unpublished work by D. Guaiana and may also be derived from publications of A. Shur only available in Russian. We also identify the (finitely many) finite binary patterns that appear non trivially, in the sense that they are obtained by applying an endomorphism that does not map the set of all segments of the sequence into itself.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
