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Seminars & Lectures

* TITLE

Intrinsic Spin Hall Effect in Semiconductors

* SPEAKERS

Name	Affiliation	E-mail
Prof. Guang-Yu Guo	National Taiwan University, Taiwan

* HOST(Applicant)

Name	Affiliation	E-mail
-

* DATE / TIME

2005-12-16, 2:30 PM

* PLACE

APCTP Seoul Brach Office

* ABSTRACT

Spin current generation is an important issue in the emerging spintronics technology. Recent proposals of the intrinsic spin Hall effect by Murakami et al [1] and Sinova et al [2], are therefore fascinating. This spin Hall effect would enable spin current generation in semiconductors without magnetic field or magnetic materials, and promise a tremendous potential of combining spintronics with the well-developed semiconductor technology. However, the recent proposals of the intrinsic spin Hall effect have been subject to careful scrutinies. In particular, Wang and Zhang [3] argued that spin symmetry consideration would rule out the possibility of such a spin current in the semiconductors described by the Luttinger Hamiltonian which was used in [1]. On the other hand, Zhang and Yang [4] point out that the intrinsic spin Hall effect predicted in [2], in a two-dimensional electron gas in semicoductors, would be exactly cancelled by the intrinsic orbital-angular-momentum Hall (orbital) effect. Therefore, fundamental questions such as the existence of the intrinsice spin Hall effect in semiconductors structures and that whether it would be cancelled out by the orbital Hall effect, remain unsolved despite enormous recent efforts.

In this talk, I will first give an introduction to the intrinsic spin Hall effect. This will then be followed by a report on our recent ab initio relativistic band theoretical calculations on the intrinsic spin Hall effect in the archetypical semiconductors Si, Ge, GaAs and AlAs [5]. Our results cover a large range of hole concentration which is beyond the validity regime of the Luttinger model. We find that intrinsic spin Hall conductivity in hole-doped semiconductors Ge, GaAl and AlAs is large, showing the possibility of spin Hall effect beyond the Luttinger Hamiltonian. The calculated orbital Hall conductivity is one order of magnitude smaller, indicating no cancellation between the spin and orbital Hall effects in bulk semiconductors. Furthermore, it is found that the spin Hall effect can be strongly manipulated by strains, and that the ac spin Hall conductivity in the semiconductors is large in pure and as well as doped semiconductors.

[1] S. Murakami, N. Nagaosa, and S.-C. Zhang, Science 301, 1348 (2003).

[2] J. Sinova et al., Phys. Rev. Lett. 92, 126603 (2004).

[3] X. Wang, and X.-G. Zhang, J. Magn. Magn. Mater. 288, 297 (2005).

[4] S. Zhang, and Z. Yang, Phys. Rev. Lett. 94, 66602 (2005).

[5] G.Y. Guo, Y. Yao, and Q. Niu, Phys. Rev. Lett. 94, 226601 (2005).

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