Korean Journal of Optics and Photonics (한국광학회지)

Optical Society of Korea (한국광학회)
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Terahertz Light Source Using Spin Angular Momentum: Spintronic Terahertz Emission

스핀 각 운동량을 이용한 테라헤르츠파 광원: 스핀트로닉 테라헤르츠 발생

  • Kyusup Lee (Department of Physics, Pukyong National University)
  • 이규섭 (국립부경대학교 물리학과)
  • Received : 2024.08.16
  • Accepted : 2024.09.24
  • Published : 2024.10.25
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Abstract

The tabletop-scale terahertz (THz) light sources using femtosecond laser pulses are primarily based on spatiotemporal changes in electron charge. This review introduces a new scheme where the spin angular momentum of electrons contributes to THz wave generation. By focusing on laser-induced spin current generation in ferromagnets, we review the outstanding characteristics observed in nanometric ferromagnetic/nonmagnetic thin films, including high power, ultra-broadband, and polarization tunability. Additionally, research on various application technologies is introduced, including the development of devices combining semiconductors, large-area THz devices, and flexible THz devices, all based on nanoscale thin films. Through this, the principle of spintronic THz emission can be understood, contributing the advancement of various application studies utilizing electron spin as a next-generation THz optical device.

펨토초 레이저 펄스를 이용한 테이블 탑(table-top) 규모의 THz파 광원은 주로 전자가 가진 전하량의 시공간적인 변화를 기반으로 한다. 본 해설논문에서는 전자가 가진 스핀 각운동량이 THz파 발생에 기여하는 새로운 방식에 대해 소개한다. 우선 강자성체(ferromagnet)에서의 레이저 유도 스핀 전류 발생에 초점을 맞추어 나노미터 두께의 강자성체/비자성체 복합 박막에서의 고출력, 광대역, 편광 자유도 등 우수한 특성을 설명한다. 또한 나노미터 두께의 박막을 기반으로 반도체 결합 소자 개발, 대면적 광 소자 개발, 플렉시블 광 소자 개발 등의 다양한 응용 기술 연구를 소개한다. 이를 통해 스핀트로닉 THz파 발생 원리를 이해하고, 차세대 THz 광 소자로서 주목받고 있는 전자의 스핀을 활용한 다양한 응용 연구를 수행하는 데 도움을 주고자 한다.

Keywords

Acknowledgement

정부(과학기술정보통신부)의 재원으로 한국연구재단의 지원을 받아 수행(Grant no. RS-2024-00454395); 2023년도 교육부의 재원으로 한국연구재단의 지원을 받는 지자체-대학 협력기반 지역혁신사업(Grant no. 2023RIS-007); 2023학년도 부경대학교의 지원을 받아 수행(202303670001).

References

  1. E. Beaurepaire, J. C. Merle, A. Daunois, and J. Y. Bigot, "Ultrafast spin dynamics in ferromagnetic nickel," Phys. Rev. Lett. 76, 4250-4253 (1996).
  2. E. Beaurepaire, G. M. Turner, S. M. Harrel, M. C. Beard, J. Y. Bigot, and C. A. Schmuttenmaer, "Coherent terahertz emission from ferromagnetic films excited by femtosecond laser pulses," Appl. Phys. Lett. 84, 3465-3467 (2004).
  3. D. J. Hilton, R. D. Averitt, C. A. Meserole, G. L. Fisher, D. J. Funk, J. D. Thompson, and A. J. Taylor, "Terahertz emission via ultrashort-pulse excitation of magnetic metalfilms," Opt. Lett. 29, 1805-1807 (2004).
  4. T. Kampfrath, M. Battiato, P. Maldonado, G. Eilers, J. Notzold, S. Mahrlein, V. Zbarsky, F. Freimuth, Y. Mokrousov, S. Blugel, M. Wolf, I. Radu, P. M. Oppeneer, and M. Munzenberg, "Terahertz spin current pulses controlled by magnetic heterostructures," Nat. Nanotechnol. 8, 256-260 (2013).
  5. M. Battiato, K. Carva, and P. M. Oppeneer, "Superdiffusive spin transport as a mechanism of ultrafast demagnetization," Phys. Rev. Lett. 105, 027203 (2010).
  6. E. Saitoh, M. Ueda, H. Miyajima, and G. Tatara, "Conversion of spin current into charge current at room temperature: Inverse spin-Hall effect," Appl. Phys. Lett. 88, 182509 (2006).
  7. K. Uchida, J. Xiao, H. Adachi, J. Ohe, S. Takahashi, J. Ieda, T. Ota, Y. Kajiwara, H. Umezawa, H. Kawai, G. E. W. Bauer, S. Maekawa, and E. Saitoh, "Spin Seebeck insulator," Nat. Mater. 9, 894-897 (2010).
  8. M. B. Jungfleisch, Q. Zhang, W. Zhang, J. E. Pearson, R. D. Schaller, H. Wen, and A. Hoffmann, "Control of terahertz emission by ultrafast spin-charge current conversion at Rashba interfaces," Phys. Rev. Lett. 120, 207207 (2018).
  9. J. C. Rojas-Sanchez, S. Oyarzun, Y. Fu, A. Marty, C. Vergnaud, S. Gambarelli, L. Vila, M. Jamet, Y. Ohtsubo, A. Taleb-Ibrahimi, P. Le Fevre, F. Bertran, N. Reyren, J. M. George, and A. Fert, "Spin to charge conversion at room temperature by spin pumping into a new type of topological insulator: α-Sn films," Phys. Rev. Lett. 116, 096602 (2016).
  10. C. Zhou, Y. P. Liu, Z. Wang, S. J. Ma, M. W. Jia, R. Q. Wu, L. Zhou, W. Zhang, M. K. Liu, Y. Z. Wu, and J. Qi, "Broadband terahertz generation via the interface inverse Rashba-Edelstein effect," Phys. Rev. Lett. 121, 086801 (2018).
  11. L. Cheng, X. Wang, W. Yang, J. Chai, M. Yang, M. Chen, Y. Wu, X. Chen, D. Chi, K. E. J. Goh, J.-X. Zhu, H. Sun, S. Wang, J. C. W. Song, M. Battiato, H. Yang, and E. E. M. Chia, "Far out-of-equilibrium spin populations trigger giant spin injection into atomically thin MoS2," Nat. Phys. 15, 347-351 (2019).
  12. T. Seifert, S. Jaiswal, U. Martens, J. Hannegan, L. Braun, P. Maldonado, F. Freimuth, A. Kronenberg, J. Henrizi, I. Radu, E. Beaurepaire, Y. Mokrousov, P. M. Oppeneer, M. Jourdan, G. Jakob, D. Turchinovich, L. M. Hayden, M. Wolf, M. Munzenberg, M. Klaui, and T. Kampfrath, "Efficient metallic spintronic emitters of ultrabroadband terahertz radiation," Nat. Photon. 10, 483-488 (2016).
  13. Y. Wu, M. Elyasi, X. Qiu, M. Chen, Y. Liu, L. Ke, and H. Yang, "High-performance THz emitters based on ferromagnetic/nonmagnetic heterostructures," Adv. Mater. 29, 1603031 (2017).
  14. T. Seifert, S. Jaiswal, M. Sajadi, G. Jakob, S. Winnerl, M. Wolf, M. Klaui, and T. Kampfrath, "Ultrabroadband single-cycle terahertz pulses with peak fields of 300 kV cm-1 from a metallic spintronic emitter," Appl. Phys. Lett. 110, 252402 (2017).
  15. R. Rouzegar, A. L. Chekhov, Y. Behovits, B. R. Serrano, M. A. Syskaki, C. H. Lambert, D. Engel, U. Martens, M. Munzenberg, M. Wolf, G. Jakob, M. Klaui, T. S. Seifert, and T. Kampfrath, "Broadband spintronic terahertz source with peak electric fields exceeding 1.5 MV/cm," Phys. Rev. Appl. 19, 034018 (2023).
  16. J. Hebling, G. Almasi, I. Z. Kozma, and J. Kuhl, "Velocity matching by pulse front tilting for large-area THz-pulse generation," Opt. Express 10, 1161-1166 (2002).
  17. H. Hirori, A. Doi, F. Blanchard, and K. Tanaka, "Single-cycle terahertz pulses with amplitudes exceeding 1 MV/cm generated by optical rectification in LiNbO3," Appl. Phys. Lett. 98, 091106 (2011).
  18. D. Kong, X. Wu, B. Wang, T. Nie, M. Xiao, C. Pandey, Y. Gao, L. Wen, W. Zhao, C. Ruan, J. Miao, Y. Li, and L. Wang, "Broadband spintronic terahertz emitter with magnetic-field manipulated polarizations," Adv. Opt. Mater. 7, 1900487 (2019).
  19. Y. Wang, H. Cheng, W. Li, Z. Liu, X. Jia, Q. Huang, and Y. Lu, "Actively switchable spintronic terahertz emission with arbitrary polarization states," Appl. Phys. Lett. 124, 091103 (2024).
  20. M. Chen, Y. Wu, Y. Liu, K. Lee, X. Qiu, P. He, J. Yu, and H. Yang, "Current-enhanced broadband THz emission from spintronic devices," Adv. Opt. Mater. 7, 1801608 (2019).
  21. U. Nandi, M. S. Abdelaziz, S. Jaiswal, G. Jakob, O. Gueckstock, S. M. Rouzegar, T. S. Seifert, M. Klaui, T. Kampfrath, and S. Preu, "Antenna-coupled spintronic terahertz emitters driven by a 1550nm femtosecond laser oscillator," Appl. Phys. Lett. 115, 022405 (2019).
  22. J. Liu, K. Lee, Y. Yang, Z. Li, R. Sharma, L. Xi, T. Salim, C. Boothroyd, Y. M. Lam, H. Yang, M. Battiato, and E. E. M. Chia, "Spintronic terahertz emitters in silicon-based heterostructures," Phys. Rev. Appl. 18, 034056 (2022).
  23. V. K. Mag-usara, M. C. Escano, C. E. Petoukhoff, G. Torosyan, L. Scheuer, J. Madeo, J. Afalla, M. L. Talara, J. E. Muldera, H. Kitahara, D. R. Bacon, M. Nakajima, K. Dani, E. T. Papaioannou, R. Beigang, and M. Tani, "Optimum excitation wavelength and photon energy threshold for spintronic terahertz emission from Fe/Pt bilayer," iScience 25, 104615 (2022).