Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session B1: Spin Hall Effect |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Naota Nagaosa, University of Tokyo Room: LACC 152 |
Monday, March 21, 2005 11:15AM - 11:51AM |
B1.00001: Dissipationless quantum spin current and the intrinsic spin Hall effect Invited Speaker: A recent theory predicts that dissipationless spin currents can be induced purely by an electric field in conventional semiconductors. The dissipationless spin current is derived from a novel topological structure in momentum space, is independent of the sample disorder and leads to the intrinsic spin Hall effect. In hole doped semiconductors, with or without inversion symmetry breaking, there are no vertex corrections due to impurities scattering, and there are no extrinsic contributions to the spin Hall effect in the clean limit. I shall analyze two recent experiments on the spin Hall effect, and show that they are both consistent with the intrinsic nature of the effect. S. Murakami, N. Nagaosa and Shou-Cheng Zhang, ``Dissipationless quantum spin current at room temperature", Science, {\{}$\backslash $bf 301{\}}, 1348 (2003). J. Sinova et. al., Phys. Rev. Lett. 92, 126603 (2004). Y. Kato et. al., Science, 11 Nov 2004 (10.1126/science.1105514). J. Wunderlich et.al., cond-mat/0410295. B. Andrei Bernevig and Shou-Cheng Zhang, cond-mat/0411457. [Preview Abstract] |
Monday, March 21, 2005 11:51AM - 12:27PM |
B1.00002: Numerical Studies of Anomalous Spin and Charge Transport Invited Speaker: In a crystal static electric fields can induce coherence between different Bloch bands. When spin-orbit interactions are included the coherence leads to spin currents that flow perpendicular to the electric field direction, and in the case of a ferromagnet to perpendicular charge currents as well. This anomalous transport thus makes a purely intrinsic contribution to the spin Hall effect, and for ferromagnets to the charge Hall effect. The robustness of these contributions in the presence of disorder has been questioned over the years, and recently for the case of the spin Hall effect of a two-dimensional electron system with Rashba spin-orbit interactions (R2DES) in particular. To address this question we have performed a numerically exact finite-size study of anomalous spin and charge transports currents for a R2DES with disorder. We find that the anomalous Hall currents are robust against disorder. In the case of a R2DES ferromagnet, the charge Hall current has additional contributions from changes in the occupation probabilities of states near the Fermi surface. We will discuss efforts to understand the total Hall conductivity of a R2DES ferromagnet in terms of intrinsic, side-jump, and skew-scattering contributions and efforts to achieve a general understanding of the circumstances under which the intrinsic contribution can dominate. [Preview Abstract] |
Monday, March 21, 2005 12:27PM - 1:03PM |
B1.00003: Resonant spin Hall effect in two dimensional electron gas Invited Speaker: Remarkable phenomena have been observed in 2DEG over last two decades, most notably, the discovery of integer and fractional quantum Hall effect. The study of spin transport provides a good opportunity to explore spin physics in two-dimensional electron gas (2DEG) with spin-orbit coupling and other interaction. It is already known that the spin-orbit coupling leads to a zero-field spin splitting, and competes with the Zeeman spin splitting if the system is subjected to a magnetic field perpendicular to the plane of 2DEG. The result can be detected as beating of the Shubnikov-de Haas oscillation. Very recently the speaker and his collaborators studied transport properties of a two-dimensional electron system with Rashba spin-orbit coupling in a perpendicular magnetic field. The spin-orbit coupling competes with the Zeeman splitting to generate additional degeneracies between different Landau levels at certain magnetic fields. It is predicted theoretically that this degeneracy, if occurring at the Fermi level, gives rise to a resonant spin Hall conductance, whose height is divergent as 1/T and whose weight is divergent as -lnT at low temperatures. The charge Hall conductance changes by 2e$^{2}$/h instead of e$^{2}$/h as the magnetic field changes through the resonant point. The speaker will address the resonance condition, symmetries in the spin-orbit coupling, the singularity of magnetic susceptibility, nonlinear electric field effect, the edge effect and the disorder effect due to impurities. This work was supported by the Research Grants Council of Hong Kong under Grant No.: HKU 7088/01P. \begin{enumerate} \item S. Q. Shen, M. Ma, X. C. Xie, and F. C. Zhang, Phys. Rev. Lett. 92, 256603 (2004) \item S. Q. Shen, Y. J. Bao, M. Ma, X. C. Xie, and F. C. Zhang, cond-mat/0410169 \end{enumerate} [Preview Abstract] |
Monday, March 21, 2005 1:03PM - 1:39PM |
B1.00004: Spin current and polarization in impure 2D electron systems with spin-orbit coupling Invited Speaker: We have considered effects of impurity potential scattering on the spin Hall conductivity of a 2D electron system, assuming that the scattering rate $\tau^{-1}$ and the spin-orbit gap $\Delta$ are small compared to the Fermi energy, but for arbitrary value of $\Delta \tau$. For a 2D electron system with pure Rashba spin-orbit coupling, or pure linear Dresselhaus coupling, we find a vanishing dc spin Hall conductivity in the bulk, for arbitrary form of the impurity potential, while non-zero spin Hall currents may occur near contacts [1]. For more general forms of the spin-orbit interaction, or for a 2D hole system in III-V materials, the bulk spin Hall conductivity should vanish in the limit of small angle impurity scattering, but may be non- zero if large-angle scattering is important. Implications of impurity scattering for spin accumulation will also be discussed. This work has been done in collaboration with E. G. Mishchenko and A. V. Shytov. [1] E. G. Mishchenko, A. V. Shytov, and B. I. Halperin, Phys. Rev. Lett. {\bf{93}}, 226602 (2004); and unpublished work. [Preview Abstract] |
Monday, March 21, 2005 1:39PM - 2:15PM |
B1.00005: Experimental observation of the spin-Hall effect in a two dimensional spin-orbit coupled semiconductor system Invited Speaker: Joerg Wunderlich The Hall effects are among the most recognized families of phenomena in basic physics and applied microelectronics. The ordinary and quantum Hall effects, which, e.g., proved the existence of positively charged carriers (holes) in semiconductors and led to the discovery of fractionally charged quasiparticles, occur due to the Lorentz force that deflects like-charge carriers towards one edge of the sample creating a voltage transverse to the current. In the anomalous Hall effect, the spin-orbit interaction plays the role of the force that deflects like-spin carriers to one edge and opposite spins to the other edge of the sample. In a ferromagnetic material this leads to a net charge imbalance between the two sides which allows to detect magnetization in the conductor by simple electrical means. Here we report the experimental discovery of a new member of the Hall family - the spin-Hall effect (SHE). As an analogue of the anomalous Hall effect but realized in non- magnetic systems the SHE opens new avenues for inducing and controlling spin-currents in semiconductors without applying magnetic fields or introducing ferromagnetic elements. To demonstrate the SHE, we have developed a novel p-n junction light emitting diode microdevice. Its co-planar geometry and the strong spin-orbit coupling in the embedded two-dimensional hole gas are well suited for inducing and detecting the SHE. When an electric field is applied across the hole layer, a non zero out-of-plane component of the spin is optically detected whose sign depends on the sign of the field and is opposite for the two edges, consistent with theory predictions. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700