Spin blockade at semiconductor/ferromagnet junctions

Abstract

We study theoretically extraction of spin-polarized electrons at nonmagnetic semiconductor/ferromagnet junctions. The outflow of majority spin electrons from the semiconductor into the ferromagnet leaves a cloud of minority spin electrons in the semiconductor region near the junction, forming a local spin-dipole configuration at the semiconductor/ferromagnet interface. This minority spin cloud can limit the majority spin current through the junction creating a pronounced spin-blockade at a critical current. We calculate the critical spin-blockade current in both planar and cylindrical geometries and discuss possible experimental tests of our predictions.Comment: to be published in PR

Current-voltage characteristics of semiconductor/ferromagnet junctions in the spin-blockade regime

“…We also show that in structures with a semiconducting region longer than the spin-diffusion length, the current density saturates to the critical current density j c found in Ref. 2. Instead, in junctions with the semiconductor region shorter than the spin-diffusion length, the asymptotic current value may be different from j c depending on how the semiconductor is connected from the opposite side of the junction.…”

“…Therefore, the majority-spin electron current through the junction becomes blocked by minority-spin electrons accumulated near the boundary. 2 This kind of spin blockade is collective and based on Coulomb interaction, while in quantum dots the spin blockade occurs on the single electron level and is due to the Pauli exclusion principle, 14 which prevents current passing through two quantum dots in series, if the spin directions of electrons in these dots are the same. 14 In this Brief Report we explore experimentally verifiable consequences of the spin-blockade phenomenon.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] In large part, this interest is motivated by the goal to exploit these phenomena in new technologies, such as spintronics and quantum computation. 1 Recently, some attention has been focused on the problem of the extraction of spin-polarized electrons from the semiconductor to the ferromagnet.…”

“…1 Recently, some attention has been focused on the problem of the extraction of spin-polarized electrons from the semiconductor to the ferromagnet. 2,[7][8][9][10][11][12][13] The importance of spin extraction was already realized in early studies of spinpolarized transport in magnetic semiconductors. 7,8 However, despite the apparent similarity of spin extraction with spin injection, the former shows unique features.…”

Spin memristive systems: Spin memory effects in semiconductor spintronics

“…4 Understanding the properties of the systems discussed in this Brief Report is of great interest in the context of actively studied spin-injection/spinextraction processes at semiconductor/ferromagnet junctions. [4][5][6][7][8][9][10][11][12][13][14] We will be interested mainly in the process of spin extraction, where the electron flow is from the semiconductor into the half metal, which is especially interesting because of the recently predicted spin-blockade phenomenon in such junctions. 4,5 The physics of the spin blockade is the following: the half metal accepts electrons of only one-say upspin direction.…”