Browsing by Author "Kleftogiannis, Ioannis"

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Finger-gate manipulated quantum transport in Dirac materials
(2015-05-27)
Kleftogiannis, Ioannis
;
Tang, Chi-Shung
;
Cheng, Shun-Jen
;
電子物理學系
;
Department of Electrophysics
We investigate the quantum transport properties of multichannel nanoribbons made of materials described by the Dirac equation, under an in-plane magnetic field. In the low energy regime, positive and negative finger-gate potentials allow the electrons to make intra-subband transitions via hole-like or electron-like quasibound states (QBS), respectively, resulting in dips in the conductance. In the high energy regime, double dip structures in the conductance are found, attributed to spin-flip or spin-nonflip inter-subband transitions through the QBSs. Inverting the finger-gate polarity offers the possibility to manipulate the spin polarized electronic transport to achieve a controlled spin-switch.
Geometrical spin manipulation in Dirac flakes
(2016-02-03)
Kleftogiannis, Ioannis
;
Amanatidis, Ilias
;
電子物理學系
;
Department of Electrophysics
We investigate numerically the spin properties of electrons in flakes made of materials described by the Dirac equation, in the presence of intrinsic spin-orbit coupling (SOC). We show that electrons flowing along the borders of flakes via edge states become helically spin-polarized for strong SOC, for materials with and without a gap at the Fermi energy, corresponding to the massive and massless Dirac equation respectively. The helically spin-polarized electrons create spin-resolved transport, controlled by the flake\'s geometry in a multi-terminal device setup. A simple analytical model containing the basic ingredients of the problem is introduced to get an insight into the helical mechanism, along with our numerical results which are based on an effective tight-binding model.