In the last decade the interest in the possibility to control and manipulate the spin of the electron for a new generation of faster devices triggered the scientific community on the investigation of materials presenting a spin-order. In this framework, topological insulators (TIs) represent a hot-topic because of the in-plane spin-polarized surface states (TSS) arising within the bulk insulating energy gap[1,2]. The inhibition of the spin-flip events[3-5] and the control of the spin polarization using ultrashort light pulses[6-8] open new scenarios in the use of this class of materials for future opto-spintronic devices.
Using time- and angle-resolved photoemission spectroscopy (TR-ARPES) on the SbxBi(2−x)SeyTe(3−y) class we studied the response of spin-polarized electrons to ultrashort circularly-polarized pulses.
Here, we report for the ﬁrst time the experimental evidence of a direct coupling between light and empty topological surface states (ESS) and the establishment of a ﬂow of spin-polarized electrons in k-space i.e. a photon-induced spin-current. In addition, our data suggest an accumulation of spin-polarized electrons in the conduction band of TIs due to the spin-dependent decay channels.
X.L. Qi and S.C. Zhang, Rev. Mod. Phys. 83, 1057 (2011).
 H. Zhang, C.X. Liu, X.L. Qi, X. Dai, Z. Fang and S.C. Zhang, Nat. Phys. 5, 438 (2009).
 Z. Alpichshev, J.G. Analytis, J.H. Chu, I.R. Fischer, Y.L. Chen, Z.X. Shen, A. Fang and A. Kapitulnik, Phys. Rev. Lett. 104, 016401 (2010).
 T. Zhang, P. Cheng, X. Chen, J.F. Jia, X. Ma, K. He, L. Wang, H. Zhang, X. Dai, Z. Fang, X. Xie and Q. K. Xue, Phys. Rev. Lett. 103, 266803 (2009).
 P. Sessi, O. Storz, T. Bathon, S. Wilfert, K. A. Kokh, O. E. Tereshchenko, G. Bihlmayer, and M. Bode,Phys. Rev. B 93, 035110.
 C. Jozwiak, C.H. Park, K. Gotlieb, C. Hwang, D.H. Lee, S.G. Louie, J.D. Denlinger, C.R. Rotundu, R.J. Birgeneau, Z. Hussain et al., Nat. Phys. 9, 293 (2013).
 Z.H. Zhu, C.N. Veenstra, S. Zhdanovich, M.P. Schneider, T. Okuda, K. Miyamoto, S.Y. Zhu, H. Namatame, M. Taniguchi, M.W. Haverkort, I.S. Elfimov and A. Damascelli, Phys. Rev. Lett. 112, 076802 (2014).
 Z. Xie, S. He, C. Chen, Y. feng, H. Yi, A. Liang, L. Zhao, D. Mou, J. He, Y. Peng et al., Nat. Commun. 5, 3382 (2014).