A Gate-Controlled Bidirectional Spin Filter Using Quantum Coherence
J. A. Folk,12*
R. M. Potok,1
C. M. Marcus,1*
V. Umansky3
We demonstrate a quantum coherent electron spin filter
by directly measuring the spin polarization of emitted current. The spin filter consists of an open quantum dot in an in-plane magnetic field; the in-plane field gives the two spin directions different Fermi
wavelengths resulting in spin-dependent quantum interference of
transport through the device. The gate voltage is used to select the
preferentially transmitted spin, thus setting the polarity of the
filter. This provides a fully electrical method for the creation and
detection of spin-polarized currents. Polarizations of emitted current
as high as 70% for both spin directions (either aligned or
anti-aligned with the external field) are observed.
1 Department of Physics, Harvard University,
Cambridge, MA 02138, USA.
2 Department of Physics,
Stanford University, Stanford, CA 94305, USA.
3 Braun Center for Submicron Research, Weizmann
Institute of Science, Rehovot 76100, Israel.
*
To whom correspondence should be addressed. E-mail:
jfolk{at}stanford.edu (J.A.F.); marcus{at}harvard.edu (C.M.M.)
