Controlling spin-to-electric charge conversion via optically-induced spin waves

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K22327
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0202:Condensed matter physics, plasma science, nuclear engineering, earth resources engineering, energy engineering, and related fields
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Yamada Kihiro 東京工業大学, 理学院, 助教 (40874722)
• Project Period (FY): 2020-09-11 – 2022-03-31
• Keywords: スピン波 / スピン流-電流変換 / フェムト秒レーザー

Outline of Final Research Achievements

By using an ultrashort optical pulse with the polarization and wavelength degrees of freedom, one can pioneer new methods for controlling spin-charge conversion phenomena and generating spin currents. In this study, we successfully measured electric currents in a Pt layer converted from spin currents originating in coherent spin waves excited by irradiating a rare-earth iron garnet film(GdYb-BIG) with a femtosecond optical pulse. The measured current is much larger than one calculated under the assumption that the electric currents result solely from the spin-pumping effect by the coherent spin waves. The light absorption by the Pt layer creates a large thermal gradient, which might promote the generation of spin currents.

Free Research Field

物性物理

Academic Significance and Societal Importance of the Research Achievements

フェムト秒光パルスを利用したスピン流-電流変換現象はサブピコ秒の時間スケールで報告があるが、フェムト秒光パルスを用いてもスピン流をナノ秒オーダーの実電流として取り出せることは、本研究が初めて実証した。得られた大きな電流はフェムト秒光パルスだからこそ励起可能なコヒーレントなスピン波および界面の熱勾配の協奏現象の存在を示唆し、本成果が光-スピン流変換の新展開へと繋がり得る。また、外部・内部電界の補助なしで光から電流が取り出せることは、光発電等への応用を考えれば重要なことである。