Electronic, Photonic and Spintronic Properties of Graphene Nanostructures
Alev Devrim Güçlü
Abstract: To create carbon-based nanoscale integrated electronic, photonic, and spintronic circuits, one must demonstrate three functionalities in a single material, graphene quantum dots (GQDs). Using many-body theoretical techniques such as configuration interaction and quantum Monte Carlo, we show that spatial confinement in GQDs opens an energy gap tunable from UV to THz, making GQDs equivalent to semiconductor nanoparticles. When connected to leads, GQDs act as single-electron transistors. The energy gap and absorption spectrum can be tuned from UV to THz by size and edge engineering and by external electric and magnetic fields. The sublattice engineering in, e.g., triangular graphene quantum dots (TGQDs) with zigzag edges generates a finite magnetic moment. The magnetic moment can be controlled by charging, electrical field, and photons. Addition of a single electron to the charge-neutral system destroys the ferromagnetic order, which can be restored by absorption of a photon. This allows for an efficient spin-photon conversion. These results show that graphene quantum dots have potential to fulfill the three functionalities: electronic, photonic, and spintronic, realized with different materials in current integrated circuits, as well as offer new functionalities unique to graphene.
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