Terahertz emission spectroscopy of YIG | topological insulator bilayers

ORAL

Abstract

Building on the demonstration of terahertz (THz) emission spectroscopy (TES) in metallic ferromagnet|normal metal heterostructures, recent works have now observed the THz emission from heterostructure bilayers of both yttrium iron garnet (YIG) | Pt and Co | Bi2Se3. We examine the energy dependence of the spin-charge conversion efficiency of THz emission in samples of a few quintuple layers of Bi2Se3 and (Bi.24Sb.76)2Te3 grown on YIG(100) and YIG(111) substrates. We excite the samples with ultrafast femtosecond light pulses of both 1.55 eV and 3.10 eV. At 1.55 eV, no electrons in YIG are excited above the band gap of 2.85 eV. When we double the photon energy to 3.10 eV, electrons in the YIG are excited into the conduction band. Since both photon energies emit THz radiation, we expect that in each case the mechanism of emission will be attributed to different effects. Specifically, with excitations of 1.55 eV, the spin current process should be predominately generated by the spin-Seebeck effect. With excitations of 3.10 eV, the generation of spin current should be dominated by the direct photoexcitation of spin-polarized charge carriers.

*Funded by NSF through 2DCC-MIP (DMR-1539916) and CEM-MRSEC (DMR-1420451)

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Presenters

  • Evan Jasper

    • Department of Physics, The Ohio State University

Authors

  • Evan Jasper

    • Department of Physics, The Ohio State University

  • John S Jamison

    • Materials Science and Engineering, The Ohio State University

  • Timothy Pillsbury

    • Department of Physics and Materials Research Institute, Pennsylvania State University
    • Materials Research Institute, Pennsylvania State University
    • Physics, Pennsylvania State University

  • Anthony R. Richardella

    • Pennsylvania State University
    • Materials Research Institute, Pennsylvania State University
    • Department of Physics and Materials Research Institute, Pennsylvania State University

  • Nitin Samarth

    • Department of Physics and Materials Research Institute, Pennsylvania State University
    • Physics, Penn State University
    • Physics, The Pennsylvania State University
    • Pennsylvania State University
    • Department of Physics, Pennsylvania State University
    • Materials Research Institute, Pennsylvania State University
    • Department of Physics, The Pennsylvania State University
    • Physics, Pennsylvania State University

  • Roberto Myers

    • Department of Materials Science and Engineering, The Ohio State University
    • Materials Science and Engineering, The Ohio State University

  • Rolando Valdes Aguilar

    • Department of Physics, The Ohio State University
    • Physics, Ohio State University