[Seminar] Giant ultrafast spin injection and spin-to-charge conversion in topological materials by Professor Elbert Chia

Abstract:

In this talk I will show terahertz (THz) emission data on spin-to-charge conversion processes in ferromagnet/topological material (TM) heterostructures, where the TM is the Bi₂Se₃ topological insulator or the monolayer 2D transition metal dichalcogenide MoS₂, both of which possess large spin-orbit coupling. In Co/Bi₂Se₃, we observe a giant THz emission that is predominantly spin-mediated, in which the topological surface states play a crucial role. We identify a 0.12-picosecond timescale that sets a technological speed limit of spin-to-charge conversion processes in topological insulators. In Co/MoS₂, by making use of the strongly out-of-equilibrium character of the injected spins, we demonstrate a highly-efficient spin injection from a ferromagnet into a semiconductor, thus overcoming the crippling problem of impedance mismatch. Astonishingly, we measure a giant spin current that is orders of magnitude larger than typical injected spin current densities using currently available techniques.

Biography:

Elbert Chia is an Associate Professor in the Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore. He obtained his PhD from the University of Illinois at Urbana-Champaign, under the supervision of Professor Myron Salamon. He then became a G. T. Seaborg Postdoctoral Fellow in Los Alamos National Laboratory, working for Dr. Antoinette Taylor. His research interests include probing the pairing symmetry of unconventional superconductors via penetration depth measurements, and ultrafast quasiparticle dynamics of strongly correlated electron systems. He published in Physical Review Letters, Physical Review X, Nature Communications, Advanced Materials, etc. He also serves in Scientific Reports as an Editorial Board Member.