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Success of Optical Control of Spin-polarized Photocurrent in Topological Insulator!

Schematics of spin-polarized photocurrent on the surfaces of TI thin films generated by optical pulses

Figure: Schematics of spin-polarized photocurrent on the surfaces of TI thin films generated by optical pulses with (a) right- and (b) left-circular polarizations. Blue circles, blue arrows, and yellow arrows show spin-polarized electrons, the direction of spin polarization and the flow direction of the photocurrent generated by optical pulses, respectively. This figure shows that the flow direction of the spin-polarized photocurrent is changed by the optical pulses with the right- and left-circular polarizations.

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November 13, 2018

The realization of spintronic devices which utilize the characteristic of spin is expected for the development of electronic devices. Topological insulators (TIs) are attractive materials in looking toward the next generation of spintronic devices.

The research group succeeded to fabricate the TI thin films oriented with crystal axis. Usually external fields such as electronic field and magnetic field are necessary to generate electric currents in materials. In this study, the researchers reveal that the spin-polarized photocurrents at the surface layer of TI polycrystalline thin films can be generated by the irradiation of the polarized light alone, which is characterized by performing time-domain terahertz (THz) wave measurement that is a non-contact method to observe THz waves radiated from photocurrents in materials.

Moreover, they demonstrate that the net flow directions of spin-polarized photocurrents can be precisely and selectively controlled by manipulating the polarization of the irradiation light.

The research group which includes Hiroaki Takeno, Graduate student, Prof. Kohji Mizoguchi, Graduate school of Science, Osaka Prefecture University, and Dr. Shingo Saito, Advanced ICT Research Institute, National Institute of Information and Communications Technology has successfully generated spin-polarized photocurrents on the surface of topological insulator (TI) thin films by light irradiation alone, without any need to external fields such as electronic field and magnetic field. This group demonstrates that the flow direction of spin-polarized photocurrents on the surface of TI thin films can be controlled by manipulating the polarization of the irradiation light (see figure).

  • Spin-polarized photocurrents are successfully generated on the surface of topological insulator (TI) thin films by light irradiation without electronic field or magnetic field.
  • We demonstrate that the flow direction of spin-polarized photocurrents can be precisely and selectively controlled by manipulating the polarization of the optical pulses.
  • These results will open the way as innovative methods to control spin-polarized electrons in optoelectronic and spintronic TI devices.

This study was published in online journal of Scientific Reports on October 18th, 2018.

The title: “Optical control of spin-polarized photocurrent in topological insulator thin films“













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