Ultrafast spin injection and spin-to-charge conversion in topological materials

14/02/2018 @ 11:00 AM – 12:00 PM Asia/Singapore Timezone
S16 Level 6 – Theory Common Conference Room
Ultrafast spin injection and spin-to-charge conversion in topological materials @ S16 Level 6 – Theory Common Conference Room

Speaker: Associate Professor Elbert Chia
Affiliation: School of Physical and Mathematical Sciences, NTU
Host: Assistant Professor Vitor M. Pereira
Location: Click HERE for directions

Abstract Details: I will demonstrate the ultrafast dynamics of spin injection and spin-to-charge conversion in topological materials. First, in a ferromagnet/topological insulator (Co/Bi2Se3) bilayer, we find a giant spin-mediated terahertz emission dominates its dynamical response. Locked to the Cobalt magnetization direction, the giant THz emission enables unprecedented tracking of the dynamical spin-charge conversion and its dependence on external device parameters that include temperature and layer thickness. For example, this allows us to identify the timescale of spin-to-charge conversion as ~0.12 ps, that sets a technological speed limit of spin-to-charge conversion processes in topological insulators, and pave the way for designing the next generation high-speed spintronic devices based on topological insulators. Second, in a ferromagnet/monolayer 2D transition metal dichalcogenide (Co/1L-MoS2) bilayer, we demonstrate efficient spin injection into a atomically thin semiconductor --- previously thought to be too inefficient and impractical --- by injecting strongly out-of-equilibrium sub-picosecond spin current pulses, and overcome the crippling problem of impedance mismatch to obtain a massive spin transfer. On top of intrinsically allowing for the transport and processing of highly time-compressed information, the giant ultrafast spin currents in semiconductors we find here naturally overcome the biggest challenge against full integration of charge and spin electronics.

About the Speaker: Elbert Chia is an Associate Professor of the School of Physical and Mathematical Sciences, Division of Physics and Applied Physics, at the Nanyang Technological University which he joined in 2007. In his research, he uses and develops ultrafast pump-probe spectroscopy as well as THz time-domain spectroscopy to probe the ultrafast quasiparticle dynamics in strongly correlated electron systems, low-temperature condensed matter physics, and penetration depth studies of unconventional superconductors. His research has covered a number of physical systems such as high-temperature superconductors (cuprates and pnictides), graphene-based materials, topological insulators, 2D transition metal dichalcogenides, organometallic halide perovskites.

Elbert received his B.Sc (Hons) 1st Class, in Mathematics from University of Auckland, New Zealand, then Postgraduate Diploma of Education (Secondary) with Distinction from the National Institute of Education, NTU. Dr Chia then obtained his MS and Ph.D. degrees in Physics from the University of Illinois at Urbana-Champaign, USA, and was a G. T. Seaborg Postdoctoral Fellow in Los Alamos National Laboratory, USA.