Spin Hall effect

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.

References

* [1] cite journal
quotes = no
author = M. I. Dyakonov and V. I. Perel,
title = Possibility of orientating electron spins with current
journal = Sov. Phys. JETP Lett.
volume = 13
issue =
pages = 467
publisher =
date = 1971
url = http://www.jetpletters.ac.ru/ps/1587/article_24366.shtml
doi =
* [2] cite journal
quotes = no
author = M.I. Dyakonov and V.I. Perel
title = Current-induced spin orientation of electrons in semiconductors
journal = Phys. Lett. A
volume = 35
issue =
pages = 459
publisher =
date = 1971
url =
doi = 10.1016/0375-9601(71)90196-4
* [3] cite journal
quotes = no
author = J.E. Hirsch
coauthors =
title = Spin Hall Effect
journal = Phys. Rev. Lett.
volume = 83
pages = 1834
date = 1999
url = http://link.aps.org/abstract/PRL/v83/p1834
doi =
format = subscription required
* [4] cite journal
quotes = no
author = M.I. Dyakonov
title = Magnetoresistance due to edge spin accumulation
journal = Phys. Rev. Lett.
volume = 99
issue =
pages = 126601
publisher =
date = 2007
url = http://link.aps.org/abstract/PRL/v99/p126601
doi =
format = abstract page
* [5] cite journal
quotes = no
author = Y. Kato
coauthors = R. C. Myers, A. C. Gossard, D. D. Awschalom
title = Observation of the Spin Hall Effect in Semiconductors
journal = Science
volume = 306
issue = 5703
pages = 1910–1913
date = 11 November 2004
url = http://www.sciencemag.org/cgi/content/full/sci;306/5703/1910
doi = 10.1126/science.1105514
pmid = 15539563
* [6] cite journal
quotes = no
author = J. Wunderlich
coauthors = B. Kaestner, J. Sinova and T. Jungwirth
title = Experimental Observation of the Spin-Hall Effect in a Two-DimensionalSpin-Orbit Coupled Semiconductor System
journal = Phys. Rev. Lett.
volume = 94
issue =
pages = 047204
date = 2005
url = http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000094000004047204000001&idtype=cvips&gifs=yes
doi =
* [7] cite journal
quotes = no
author = A.A. Bakun
coauthors = B.P. Zakharchenya, A.A. Rogachev, M.N. Tkachuk, and V.G. Fleisher
title = Detection of a surface photocurrent due to electron optical orientation in a semiconductor
journal = Sov. Phys. JETP Lett.
volume = 40
issue =
pages = 1293
date = 1984
url = http://www.jetpletters.ac.ru/ps/1262/article_19087.shtml
doi =
* [8] cite journal
quotes = no
author = H. Zhao
coauthors = E. J. Loren, H. M. van Driel, and A. L. Smirl
title = Coherence Control of Hall Charge and Spin Currents
journal = Phys. Rev. Lett.
volume = 96
pages = 246601
date = 2006
url = http://link.aps.org/abstract/PRL/v96/e246601
doi = 10.1103/PhysRevLett.96.246601
format =
* [9] cite journal
quotes = no
author = S.O. Valenzuela
coauthors = M. Tinkham
title = Direct Electronic Measurement of the Spin Hall Effect
journal = Nature
volume = 442
pages = 176
date = 2006
url = http://www.nature.com/nature/journal/v442/n7099/abs/nature04937.html
doi = 10.1038/nature04937
format =
* [10] cite journal
quotes = no
author = T. Kimura
coauthors = Y. Otani, T. Sato, S. Takahashi, and S. Maekawa
title = Room-Temperature Reversible Spin Hall Effect
journal = Phys. Rev. Lett.
volume = 98
pages = 156601
date = 2007
url = http://link.aps.org/abstract/PRL/v98/e156601
doi = 10.1103/PhysRevLett.98.156601
format =