Ultrafast Spin‐to‐Charge Conversion at the Surface of Topological Insulator Thin Films

• DOI: 10.1002/adma.201802356
• Publication Date: 2018-10-29T07:55:41Z
• Authors: Xinbo Wang; Liang Cheng; Dapeng Zhu; Yang Wu; Mengji Chen; Yi Wang; Daming Zhao; Chris B. Boothroyd; Yeng Ming Lam; Jian‐Xin Zhu; Marco Battiato; Justin C. W. Song; Hyunsoo Yang; Elbert E. M. Chia
• Keywords: Topological insulator; Surface charge; Surface States

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 dynamics that govern it have remained elusive. Here, an all-optical method is presented, which enables unprecedented tracking ultrafast a prototypical insulator Bi2 Se3 /ferromagnetic Co heterostructure, down to sub-picosecond timescale. Compared pure or Co, giant terahertz emission observed heterostructure originates from conversion, states play crucial role. A 0.12 ps timescale identified sets technological speed limit processes insulators. In addition, shown efficiency temperature independent as expected nature paving way for designing next-generation high-speed optospintronic devices based on at room temperature.