Spin Hall effect
From Wikipedia, the free encyclopedia
The Spin Hall Effect (SHE) is a transport phenomenon predicted by the Russian physicists M.I. Dyakonov and V.I. Perel in 1971 [1,2]. It consist of an appearance of spin accumulation on the latteral surfaces of a current-carrying sample, the signs of the spin directions being opposite on the opposing boundaries. In a cylindrical wire, the current-induced surface spins will wind around the wire. When the current direction is reversed, the directions of spin orientation is also reversed.
The term "Spin Hall Effect" was introduced by Hirsch [3] in 1999. Indeed, it is somewhat similar to the classical Hall effect, where charges of opposite sign appear on the opposing lateral surfaces to compensate for the Lorentz force, acting on electrons in an applied magnetic field. However, no magnetic field is needed for SHE. On the contrary, if a strong enough magnetic field is applied in the direction perpendicular to the orientation of the spins at the surfaces, SHE will disappear because of the spin precession around the direction of the magnetic field [2,4].
Experimentally, the Spin Hall Effect was observed in semiconductors [5,6] more that 30 years after the original prediction. The spin accumulation induces circular polarization of the emitted light, as well as the Faraday (or Kerr) polarization rotation of the transmitted (or reflected) light, which allows to monitor SHE by optical means.
The origin of SHE is in the spin-orbit interaction, which leads to the coupling of spin and charge currents: an electrical current induces a transverse spin current (a flow of spins) and vice versa [1,2,4]. One can intuitively understand this effect by using the analogy between an electron and a spinning tennis ball, which deviates from its straight path in air in a direction depending on the sense of rotation (the Magnus effect).
The Inverse Spin Hall Effect, an electrical current induced by a spin flow due to a space dependent spin polarization, was first observed in 1984 [7]. More recently, the existence of both direct and inverse effects was demonstrated not only in semiconductors[8], but also in metals [9,10].
The SHE belongs to the same family as the anomalous Hall effect, known for a long time in ferromagnets, which also originates from spin-orbit interaction. The details of the microscopic mechanism leading to these phenomena are not yet completely understood.
The SHE might be used to manipulate electron spins electrically, however so far no practical applications are known.
[edit] References
- [1] M. I. Dyakonov and V. I. Perel, (1971). On the possibility of spin orientation of electrons by current. Sov. Phys. JETP Lett. 13: 467.
- [2] M.I. Dyakonov and V.I. Perel (1971). Current-induced spin orientation of electrons in semiconductors. Phys. Lett. A 35: 459.
- [3] J.E. Hirsch (1999). Spin Hall Effect (subscription required). Phys. Rev. Lett. 83: 1834.
- [4] M.I. Dyakonov (2007). Magnetoresistance due to edge spin accumulation (abstract page). Phys. Rev. Lett. 99: 126601.
- [5] Y. Kato; R. C. Myers, A. C. Gossard, D. D. Awschalom (11 November 2004). Observation of the Spin Hall Effect in Semiconductors. Science 306 (5703): 1910–1913. doi:. PMID 15539563.
- [6] J. Wunderlich; B. Kaestner, J. Sinova and T. Jungwirth (2005). Experimental Observation of the Spin-Hall Effect in a Two-DimensionalSpin-Orbit Coupled Semiconductor System. Phys. Rev. Lett. 94: 047204.
- [7] A.A. Bakun; B.P. Zakharchenya, A.A. Rogachev, M.N. Tkachuk, and V.G. Fleisher (1984). Detection of a surface photocurrent due to electron optical orientation in a semiconductor. Sov. Phys. JETP Lett. 40: 1293.
- [8] H. Zhao; E. J. Loren, H. M. van Driel, and A. L. Smirl (2006). Citation is missing a .
Either specify one, or click here and a bot will complete the citation details for you. [1] (abstract page). Phys. Rev. Lett. 96: 246601.
- [9] S.O. Valenzuela; M. Tinkham (2006). Direct Electronic Measurement of the Spin Hall Effect (abstract page). Nature 442: 176. doi:.
- [10] T. Kimura; Y. Otani, T. Sato, S. Takahashi, and S. Maekawa (2007). Citation is missing a .
Either specify one, or click here and a bot will complete the citation details for you. [2] (abstract page). Phys. Rev. Lett. 98: 156601.
