A Gate-Controlled Bidirectional Spin Filter Using Quantum Coherence

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Science  31 Jan 2003:
Vol. 299, Issue 5607, pp. 679-682
DOI: 10.1126/science.1078419

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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.

  • * To whom correspondence should be addressed. E-mail: jfolk{at} (J.A.F.); marcus{at} (C.M.M.)

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