Magnetic properties of graphene quantum dots
Abstract
Using the tightbinding approximation we calculated the diamagnetic susceptibility of graphene quantum dots (GQDs) of different geometrical shapes and characteristic sizes of 210 nm, when the magnetic properties are governed by the electron edge states. Two types of edge states can be discerned: the zeroenergy states (ZESs), located exactly at the zeroenergy Dirac point, and the dispersed edge states (DESs), with the energy close but not exactly equal to zero. DESs are responsible for a temperatureindependent diamagnetic response, while ZESs provide a temperaturedependent spin paramagnetism. Hexagonal, circular, and randomly shaped GQDs contain mainly DESs, and, as a result, they are diamagnetic. The edge states of the triangular GQDs are of ZES type. These dots reveal the crossover between spin paramagnetism, dominating for small dots and at low temperatures, and orbital diamagnetism, dominating for large dots and at high temperatures.
 Publication:

Physical Review B
 Pub Date:
 May 2013
 DOI:
 10.1103/PhysRevB.87.205434
 arXiv:
 arXiv:1301.7138
 Bibcode:
 2013PhRvB..87t5434E
 Keywords:

 73.22.Pr;
 73.21.La;
 75.20.g;
 75.75.c;
 Quantum dots;
 Diamagnetism paramagnetism and superparamagnetism;
 Condensed Matter  Mesoscale and Nanoscale Physics
 EPrint:
 Phys. Rev. B 87, 205434 (2013)