Programme

O.10 -- Oral, NCTP-39

Date: Tuesday, 29-07-2014

Time: 14h20 - 14h40

Fock-Darwin energy spectrum of the gate-tunable circular graphene quantum dots

Nguyễn Thị Thùy Nhung (1), Bùi Thị Hạnh (1)

(1) Theoretical and Computational Physics Department, Institute of Physics, VAST, 10 Dao Tan, Ba Dinh Distr., Hanoi 10000, Vietnam

The energy spectrum of the gate-tunable circular graphene quantum dots in a perpendicular magnetic field is systematically studied. To this end we suggest an alternative model of the Gaussian confinement potential with the strength $U_0$ describing the gate voltage and the typical half-width d measuring the dot radius. In the absence of magnetic fields it was shown that despite the Klein tunneling the Gaussian confinement potential can create the quasi-bound states (QBSs) in the sense that their life-time is long enough for practical purposes. For a given dot, i.e. given $U_0$ and $d$, the larger the angular momentum m of the state the longer its life-time becomes and, typically, the states with $m \ge 5$ could be well considered as quasi-bound. While the QBS life-time increases as the dot radius reduces, it may be effectively turned by the gate voltage. In the presence of a magnetic field, calculations show the Fock-Darwin energy spectrum for the dots with different $d$ and $U_0$. In general, magnetic fields enhance the localization of QBSs, the field effects are however depending on not only the value of $m$ but also its sign. In particular, for QBSs with negative angular momenta, the magnetic field may induce the delocalization-localization transition.

Presenter: Nguyễn Thị Thuỳ Nhung