Ultrafast Spin-to-Charge Conversion in Topological-insulator/Ferromagnet Heterostructures

ORAL

Abstract

Strong spin-orbit coupling, resulting in the formation of spin-momentum-locked surface states in topological insulators (TIs), is predicted to possess superior spin-to-charge conversion (SCC) efficiency via the inverse Rashba-Edelstein effect and/or inverse spin Hall effect. The knowledge of the timescale of such SCC processes is crucial for the optimization of TI-based spintronic devices. Here, we investigate the ultrafast SCC in topological-insulator/ferromagnet heterostructures via terahertz emission spectroscopy. We demonstrate highly-efficient THz emission from Bi2Se3/Co heterostructures, where the surface states play a dominant role. Compared to the instantaneous shift current terahertz emission mechanism in Bi2Se3, we directly observe a temporal delay in the spin-current-related component — 0.12 ps, which characterizes the SCC timescale in TIs. In addition, we show that the SCC efficiency is temperature independent in Bi2Se3 as expected from the nature of the surface states. Our study provides fundamental insights into the ultrafast SCC processes, and demonstrate the practical applications of TIs, especially the surface states, in terahertz spintronic devices at room temperature.

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Presenters

  • Xinbo Wang

    Division of Physics and Applied Physics, Nanyang Technological University

Authors

  • Xinbo Wang

    Division of Physics and Applied Physics, Nanyang Technological University

  • Liang Cheng

    Division of Physics and Applied Physics, Nanyang Technological University, School of Physical and Mathematical Sciences, Nanyang Technological University

  • Dapeng Zhu

    Department of Electrical and Computer Engineering, National University of Singapore, Dept. of Electrical and Computer Engineering, National Univ. of Singapore

  • Yang Wu

    Department of Electrical and Computer Engineering, National University of Singapore

  • Mengji Chen

    Department of Electrical and Computer Engineering, National University of Singapore

  • Daming Zhao

    Division of Physics and Applied Physics, Nanyang Technological University

  • Jian-Xin Zhu

    Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos National Laboratory, Los Alamos National Laboratory, Theoretical Division, Theoretical Division, Los Alamos National Laboratory, Los Alamos Natl Lab

  • Justin Song

    Nanyang Technological University, Division of Physics and Applied Physics, Nanyang Technological University, School of Physical and Mathematical Sciences, Nanyang Technological University

  • Marco Battiato

    Institute of Solid State Physics, Vienna University of Technology

  • Hyunsoo Yang

    National University of Singapore, Department of Electrical and Computer Engineering, National University of Singapore, Dept. of Electrical and Computer Engineering, National Univ. of Singapore, Electrical and Computer Engineering, National University of Singapore

  • Ee Min Chia

    Division of Physics and Applied Physics, Nanyang Technological University, School of Physical and Mathematical Sciences, Nanyang Technological University, Division of Physics and Applied Physics, Nanyang Tech Univ