A gate-controlled bidirectional spin filter using quantum coherence.
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.
Folk
J A
JA
Department of Physics, Harvard University, Cambridge, MA 02138, USA. jfolk@stanford.edu
Potok
R M
RM
Marcus
C M
CM
Umansky
V
V