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Spin-orbit torques and spin Hall effect – describing them via the gauge potential picture

Speaker: 
Mansoor B. A. Jalil (CA2DM & Faculty of Engineering, NUS)
Date: 
Wed, 11/05/2016 - 11:00am to 12:00pm
Location: 
Physics Conference Room (S11-02-07)
Event Type: 
Seminars

Abstract

The concepts of gauge fields and gauge symmetry are pervasive in modern physics [1]. Recently, the concepts of gauge potentials have been introduced to the field of spintronics as a means to describe spin transport and dynamics, especially in spin-orbit coupling systems [2,3]. In this talk, I will present the gauge field description of spin-orbit torques (SOT). At present, SOT is being heavily-researched as it can potentially lead to a highly efficient method of switching magnetic memories. The phenomenon of SOT was first predicted by us in a Rashba system in 2007, via the gauge field description [4,5]. The SOT formula was later re-derived via the equivalent Boltzmann model by Manchon in 2008 [6], and since then has been experimentally investigated in a variety of systems, beginning with a heavy metal interfacial system in 2010 [7]. I will also present the gauge description of SOT in other two-dimensional systems like graphene [8] and topological insulators [9]. Secondly, I would also describe the application of gauge theory to the spin Hall effect (SHE) [10,11], and introduce the associated concept of the Yang-Mill’s spin motive force [12]. Finally, the equivalence to the Kubo treatment will be discussed [13].

[1] C. N. Yang, Physics Today 67, 45 (2014).
[2] T. Fujita, M. B. A. Jalil, S. G. Tan, and S. Murakami, Journal of Applied Physics 110, 121301 (2011).
[3] S. G. Tan and M. B. A. Jalil, Introduction to the Physics of Nanoelectronics (Elsevier, ISBN 9780857095114, 2012).
[4] S. G. Tan, M. B. A. Jalil, and X.-J. Liu, arXiv preprint arXiv:0705.3502 (2007).
[5] S. G. Tan, M. B. A. Jalil, T. Fujita, and X.-J. Liu, Annals of Physics 326, 207 (2011).
[6] A. Manchon and S. Zhang, Physical Review B 78, 212405 (2008).
[7] I. M. Miron et al., Nature 476, 189 (2011).
[8] J. Chen, M. B. A. Jalil, and S. G. Tan, AIP Advances 3, 062127 (2013).
[9] J. Chen, M. B. A. Jalil, and S. G. Tan, Journal of the Physical Society of Japan 83, 064710 (2014).
[10] S. G. Tan and M. B. A. Jalil, Journal of the Physical Society of Japan 82, 094714 (2013).
[11] S. G. Tan, M. B. Jalil, C. S. Ho, Z. Siu, and S. Murakami, Scientific Reports 5, 18409 (2015).
[12] C. S. Ho, M. B. A. Jalil, and S. G. Tan, EPL (Europhysics Letters) 107, 37005 (2014).
[13] D. Xiao, M.-C. Chang, and Q. Niu, Reviews of Modern Physics 82, 1959 (2010).

About the speaker

Mansoor B. A. Jalil is an Associate Professor of the NUS Department of Electronic and Computer Engineering. His expertise in the theory of nanoscale electronic devices, particularly electronic charge and spin transport, is reflected in more than 200 journal publications and several book contributions in this field, and is recognized by various research-based awards over the years. Mansoor’s research interests comprise topics such as (i) semiconductor spintronics, including spin-orbit effects, spin Hall effect, and spin injection, (ii) metal-based spintronics, including spin transfer switching, magnetic random access memory, and spin-orbit coupling effects, (iii) transport in graphene devices including Klein tunneling, helical and magnetoresistive transport, (iv) topological insulators, including spin torque and magnetoresistance.

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