Abstract
In this talk, we shall first briefly summarize the theoretical and experimental situation concerning the spin Hall effect in graphene. The early attempts [1] to deliver a theory that explains the spin transport experiments performed by the Singapore group [2] in terms of a resonant enhancement of the skew scattering mechanism will be subsequently discussed.
This theory will then critically reassessed and extended to correctly capture the quantum coherent spin dynamics of the carriers. We shall discuss the results obtained from a more complete version of the theory [3,5] which relies on a quantum Boltzmann equation that correctly captures the spin coherence of the carriers scattering with a dilute ensemble of adatom impurities. This theory predicts that graphene and possibly other systems with fluctuating spin orbit coupling, can sustain a current-induced spin polarization (CISP). We find that there are two extrinsic mechanisms contributing to the CISP. The first one is an extrinsic version of the Edelstein effect. The second mechanism, which often dominates the Edelstein effect, provides a direct coupling between the electric current and magnetization and it is caused by the polarizing effect of scattering off spin-orbit impurities in a two-dimensional system. Finally, I will discuss how the new theory could shed light on the experimental situation as well as possible additional contributions to the measured nonlocal signals [2,4] arising from sources other than spin orbit coupling.
References:
[1] A. Ferreira, T. Rappoport, M. A. Cazalilla, and A. H. Castro Neto, Phys. Rev. Lett 112, 066601 (2014); H.-Y. Yang, C. Huang, H. Ochoa, and M. A. Cazalilla, Phys. Rev. B 93, 085418 (2014).
[2] J. Balakrishnan et al, Nature Communications 5, 4748 (2014); J. Balakrishnan et al. Nature Physics 9, 284 (2013).
[3] C. Huang, Y. Chong, and M. A. Cazalilla, report arXiv:1603.08107 (2016).
[4] A. A. Kaverzin and B. J. van Wees, Phys. Rev. B 91, 1652412 (2015); Y. Wang, X. Cai, J. Reutt-Robey, and M. S. Fuhrer, Phys. Rev. B 92, 161411 (2015).
[5] X.-P. Zhang, C. Huang, and M. A. Cazalilla, arXiv:1611.02382 (2016).
Coffee and tea will be served 20 minutes prior to the seminar.
Anyone interested is welcome to attend.