Electronic, magnetic and transport properties of graphene quantum dots with charged impurities
tarafından
 
Polat, Mustafa, author.

Başlık
Electronic, magnetic and transport properties of graphene quantum dots with charged impurities

Yazar
Polat, Mustafa, author.

Yazar Ek Girişi
Polat, Mustafa, author.

Fiziksel Tanımlama
xiv, 71 leaves: charts;+ 1 computer laser optical disc.

Özet
In this thesis, electronic, magnetic, and transport properties of armchair edged hexagonal and zigzag edged triangular graphene quantum dots (GQDs) are investigated in the presence of charged impurities. In this manner, a special attention has been paid to the Coulomb impurity problem in these structures. The collapse of the wave functions starting from the 1S$_{1/2}$ state is studied in the presence of not only the Coulomb impurity but also in the presence of a Coulomb charged vacancy with the help of tight-binding and extended mean-field Hubbard (MFH) models. Here, we report an interaction induced renormalization of the critical coupling constant ($\beta_{c}$). In addition, our results suggest that the induced charge for the interacting fermions is smaller than that of the non-interacting fermions. Furthermore, the transport coefficients reveal two different characteristics of the subcritical ($\beta$ $<$ $\beta_{c}$) and supercritical ($\beta$ $>$ $\beta_{c}$) regimes. As for the charged vacancy, the bare carbon vacancy induces a local magnetic moment in the hexagonal GQDs, but it is suppressed when the vacancy is charged with the subcritical Coulomb potential. Except the pristine cases of the GQDs, we numerically study a Coulomb impurity problem for the interacting fermions restricted in disordered hexagonal GQDs. In the presence of randomly distributed lattice defects and spatial potential fluctuations induced by Gaussian impurities, the response of $\beta_{c}$ for atomic collapse is mainly investigated by local density of states (LDOS) calculations within the MFH model. We find that both types of disorder cause an amplification of the critical threshold. As for the zigzag edged triangular GQDs, in the presence of the bare vacancy, we exactly obtain the spin splitting with the help of LDOS calculations in the energy spectrums, which are dominated by the edge states around the Fermi level. Similar to the hexagonal GQDs, if the vacancy is charged, the local magnetic moment disappears in these GQDs.

Konu Başlığı
Quantum dots.
 
Graphene.

Yazar Ek Girişi
Güçlü, Alev Devrim

Tüzel Kişi Ek Girişi
İzmir Institute of Technology. Phiysics.

Tek Biçim Eser Adı
Thesis (Doctorale)--İzmir Institute of Technology:Phiysics.
 
İzmir Institute of Technology:Phiysics--Thesis (Doctoral).

Elektronik Erişim
Access to Electronic Versiyon.


LibraryMateryal TürüDemirbaş NumarasıYer NumarasıDurumu/İade Tarihi
IYTE LibraryTezT002254QC611.6.Q35 P76 2020Tez Koleksiyonu