https://doi.org/10.1140/epjb/e2005-00103-x
Mesoscopic spin-flip transport through a quantum dot system responded by ac magnetic fields
1
Department of Physics, The University of Hong Kong, Pokfulam
Road, Hong Kong, China
2
Department of Physics, Beijing Institute of Technology,
Beijing 100081, China
Corresponding author: a zhaohonk@yahoo.com
Received:
23
November
2004
Revised:
21
December
2004
Published online:
16
April
2005
We investigate mesoscopic spin transport through a quantum dot
(QD) responded by a rotating and an oscillating magnetic
fields. The rotating magnetic field rotates with the angular
frequency 
around the z-axis with the tilt angle
θ, while the time-oscillating magnetic field is located in
the z-axis with the angular frequency ω. The spin flip is
caused by the rotating magnetic field, and it is the major source
of spin current. The Zeeman effect is contributed by the two field
components, and it is important as the magnetic fields are strong.
The oscillating magnetic field takes significant role due to the
spin-photon pumping effect, and the spin current can be generated
by it even as 
for the tilt angle
. The peak and valley structure appears with respect
to the frequency ω of oscillating field. The generation of
spin current is companying with charge current. Spin current
displays quite different appearance between the cases in the
absence of source-drain bias (eV=0) and in the presence of
source-drain bias (
). The symmetric spin current
disappears to form asymmetric spin current with a negative valley
and a positive plateau. The charge current is mainly determined by
the source-drain bias, photon absorption, and spin-flip effect.
This system can be employed as an ac charge-spin current
generator, or ac charge-spin field effect transistor.
PACS: 85.35.-p – Nanoelectronic devices / 73.23.-b – Electronic transport in mesoscopic systems / 72.25.Mk – Spin transport through interfaces / 73.21.La – Quantum dots
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2005
