Journal
ADVANCED MATERIALS
Volume 30, Issue 52, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.201802356
Keywords
spin-to-charge conversion; spintronics; surface states; terahertz emission spectroscopy; topological insulators
Categories
Funding
- A*Star PHAROS Programme on Topological Insulators and 2D Materials (SERC) [152 74 00026, 152 70 00016]
- Singapore Ministry of Education AcRF [MOE2015-T2-2-065]
- U.S. DOE BES Core Program LANL-E3B5
- Singapore National Research Foundation (NRF) [NRF-NRFF2016-05]
- Nanyang Technological University through a SUG Grant
- Austrian Science Fund (FWF) [M1925-N28]
- Nanyang Technological University NAP-SUG Grant
- Center for Integrated Nanotechnologies, a U.S. DOE BES user facility
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Strong spin-orbit coupling, resulting in the formation of spin-momentum-locked surface states, endows topological insulators with superior spin-to-charge conversion characteristics, though the dynamics that govern it have remained elusive. Here, an all-optical method is presented, which enables unprecedented tracking of the ultrafast dynamics of spin-to-charge conversion in a prototypical topological insulator Bi2Se3/ferromagnetic Co heterostructure, down to the sub-picosecond timescale. Compared to pure Bi2Se3 or Co, a giant terahertz emission is observed in the heterostructure that originates from spin-to-charge conversion, in which the topological surface states play a crucial role. A 0.12 ps timescale is identified that sets a technological speed limit of spin-to-charge conversion processes in topological insulators. In addition, it is shown that the spin-to-charge conversion efficiency is temperature independent in Bi2Se3 as expected from the nature of the surface states, paving the way for designing next-generation high-speed optospintronic devices based on topological insulators at room temperature.
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