Abstract
Topological Insulators (TI) represent a hot-topic for both basic physics and promising applications because of the in-plane spin-polarized surface states (TSS) arising within the bulk insulating energy gap. The backscattering protection and the control of the spin polarization using ultrashort light pulses open new scenarios in the use of this class of materials for future opto-spintronic devices. Using time- and angle-resolved photoemission spectroscopy on 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.
Highlights
In the last years, topological insulators have become a hot-topic as benchmark for novel theoretical and experimental studies in spintronics
We found a common trend of the dichroism in several compounds of SbxBi(2−x)SeyTe(3−y) class suggesting a universal property
The electrons of the opposite spin do not accumulate in bulk band (BB) due to the high energy and they decay into the first lower energy accessible band, i.e. the conduction band
Summary
Topological insulators have become a hot-topic as benchmark for novel theoretical and experimental studies in spintronics. Because circularly-polarized light couples to the total angular momentum of electron (i.e. orbital momentum + spin), we performed time and angle-resolved photoemission spectroscopy (TRARPES) measurements using linear p-polarized pump beam and circularly-polarized probe beam. In this way we can reveal a spin-related parameter of the spin-polarized band structure. In this configuration the selectivecoupling of helicities of light with spin leads to a spin-selective pumping
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