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Condensed Matter Seminars
| Condensed Matter
Thursday, September 29, 2005
Physics Building, Room 204
Note special time.
Note special room.
[Host: Yongsoo Yoon]
"Spin Separation in Cyclotron Motion"
We demonstrate spatial separation of carriers with opposite spin
orientations in a non-magnetic semiconductor. An ability to
manipulate spin of charge carries in a controllable fashion is
central to the rapidly developing field of spintronics, as well as
for the development of spin-based devices for quantum information
processing. However, creation of spin-polarized currents is proven
to be a formidable challenge and, previously, required either
injection from magnetic materials or application of strong Zeeman
magnetic field. We show that in a non-magnetic semiconductor with
spin-orbit interactions spins can be spatially separated in a
“spin spectrometer”, utilizing difference in momenta and, thus,
cyclotron radii, for two spin polarizations. For holes in GaAs
almost 100% bipolar spin filtering has been achieved in magnetic
focusing geometry with spatial separation of polarized beams by
0.2 microns. We confirmed spin polarization of the injected
currents by applying strong Zeeman field and using point contacts
as spin filters. Spin-orbit interaction constant has been measured
directly in these experiments. The new technique of spin
injection/detection opens a possibility to investigate density and
electric field dependence of spin-orbit interactions, spin
dynamics at a few tenths of picoseconds without RF fields, and
shed light on such outstanding problems as “0.7 anomaly” in
quantum point contacts by measuring spin polarization of charge
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