Spin accumulation in the extrinsic spin hall effect

Abstract

Bipolar spintronics, typically realized in systems which include semiconductors, is an emerging subfield of spintronics in which carriers of both polarities (electrons and holes) are important. In contrast to unipolar spintronics, characteristic for metallic systems, there are large deviations from local charge neutrality and intrinsic non-linearities in the current-voltage characteristics, which are important even at small applied bias. Together with the ease of manipulating the minority charge carriers (electrons and holes), these distinguishing features of bipolar spintronics are suitable for realizing active devices which could amplify signals and provide an additional degree of control not available in charge-based electronics. Spin-polarized bipolar transport can be thought of as a generalization of its unipolar counterpart. Specifically, spin-polarized unipolar transport can then be obtained as a limiting case by setting the electron-hole recombination rate to zero and considering only one type of carrier (either electrons or holes).