Abstract
We investigate the electronic and transport properties of circular graphene structures (quantum dots) that include a pentagonal defect. In our calculations, we employ a tight-binding model determining total and local density of states, transmission function and participation number. For the closed structure, we observe that the effect of the defect is concentrated mainly on energies near to zero, which is characteristic of edge states in graphene. The density of states and transmission functions for small energies show several peaks associated with the presence of quasi-bound states generated by the defect and localized edge states produced by both the circular boundaries of the finite lattice and induced by the presence of the pentagonal defect. These results have been checked by calculating the participation number, which is obtained from the eigenstates. We observe changes in the available quasi-bound states due to the defect and the creation of new peaks in the transmission function.
Highlights
The theoretical and experimental study of properties of graphene has attracted the attention of many authors in the last few years since a method to isolate single graphene layers was developed
We have calculated the total density of states, which is shown in Figure 2, for both the defect-free structure and with Pentagonal defect (PD)
We see that the density for the structure with PD shows a shoulder near E = 0, indicating the existence of additional edge states induced by the presence of the PD and the circular shape of the structure
Summary
The theoretical and experimental study of properties of graphene has attracted the attention of many authors in the last few years since a method to isolate single graphene layers was developed (the authors Geim and Novoselov were awarded with the Nobel prize). These graphene sheets may be stable enough to be freely suspended [1], which allows us to use them in solid state experiments. The electronic properties of graphene are surprising: one finds new quasi-particles described by the Dirac equation at low energies that behave like massless particles This opens the possibility to study quantum electrodynamics properties in solid-state devices and to carry out new developments, e. Other authors made similar studies to ours but considered different
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