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橋本佑介 A,B 三野弘文 A 、山室智文 A 、蒲原俊樹 A 、神原大蔵 A 、松末俊夫 B Jigang Wang C 、 Chanjuan Sun C 、河野淳一郎 C 、嶽山正二郎 D

13aXD-14. 希薄磁性半導体 CdMnTe における強励起効果. High excitation effects in dilute magnetic semiconductor CdMnTe. 橋本佑介 A,B 三野弘文 A 、山室智文 A 、蒲原俊樹 A 、神原大蔵 A 、松末俊夫 B Jigang Wang C 、 Chanjuan Sun C 、河野淳一郎 C 、嶽山正二郎 D 千葉大院自然 A 、千葉大工 B 、ライス大 ECE C 、東大物研 D Y. Hashimoto A,B

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橋本佑介 A,B 三野弘文 A 、山室智文 A 、蒲原俊樹 A 、神原大蔵 A 、松末俊夫 B Jigang Wang C 、 Chanjuan Sun C 、河野淳一郎 C 、嶽山正二郎 D

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  1. 13aXD-14 希薄磁性半導体CdMnTeにおける強励起効果 High excitation effects in dilute magnetic semiconductor CdMnTe 橋本佑介A,B 三野弘文A、山室智文A、蒲原俊樹A、神原大蔵A、松末俊夫B Jigang WangC、Chanjuan SunC、河野淳一郎C、嶽山正二郎D 千葉大院自然A、千葉大工B、ライス大ECEC、東大物研D Y. HashimotoA,B H. MinoA, T. YamamuroA, T. KamoharaA, D. KanbaraA, T. MatsusueB, J. WangC, C. SunC, J. KonoC, S. TakeyamaD Graduate School of Science and Technology, Chiba Univ.A 、 Department of Engineering, Chiba Univ.B, ECE Dept., Rice Univ.C 、ISSP, Univ. of TokyoD

  2. h e Magnetic Polarons Free Exciton Magnetic Polaron (FEMP) Mn spin Exciton spin A Golnic, et. al. J. Phys. C16, 6073 (1983) M. Umehara, Phys. Rev. B 68, 193202 (2003) Localization only by sp-d exchange interaction Photo-induced ferromagnetism via the FEMP

  3. x = 5 ~ 10% → FEMP energy : Large Alloy potential fluctuation : Small Free exciton magnetic polaron (FEMP) in CdMnTe Localization energy of Magnetic Polaron Current work : Alloy Potential fluctuation Localization energy High quality CdMnTe sample with low Mn concentration He-Ne laser 76 MHz Ti:Sapphire laser 250 kHz OPA laser 1 kHz OPA laser Exciton density 1012 – 1020 [cm-3] CW and Time-resolved Photoluminescence 5 10 Mn Concentration [%] S. Takeyama, J. of Crys. Growth, 184-185 (1998) 917-920

  4. Free Exciton Magnetic Polarons Bipolaron FEMP Ferromagnetic Phase Transition via Free Exciton Magnetic Polarons ?

  5. Cd0.95Mn0.05Te Cd1-yMgyTe GaAs Experimental Setup for PL measurements Bulk Cd1-xMnxTe x = 5% Laser CCD or Streak camera Spectro-meter Sample 1.4 K

  6. n 1019 1020 1016 1017 1013 1014 1015 1018 1012 rs 0.1 1 2 100 10 Lasers Excitation intensity: 1mW, Focus size: 200mm, O.D. 1 1 kHz OPA Ti: Sapphire 250 kHz OPA He-Ne aB = 6.7 nm  nMott = 7.9 x 1017 [cm-3]

  7. Absorption Photoluminescence Photon energy [eV] Low Excitation Limit Exciton Density 1012 - 1014 [cm-3] 1020 1 kHz OPA 1019 Absorption: 4.2 K, PL: 1.4K PL Light source：He-Ne 633nm 1018 250 kHz OPA 1017 1016 Ti: S Distinct PL line of the FEMP appear !! FEMP binding energy  1.8 meV 1015 1014 BX He-Ne 1013 1012

  8. Photoluminescence Exciton Density 1015 – 1016 [cm-3] Excitation intensity normalized PL Exciton density 1015, 1016[cm-3] 1020 1 kHz OPA 1019 1018 250 kHz OPA 1017 BX 1016 Ti:S 1015 1014 He-Ne 1013 FEMP PL intensity: Saturate FX PL intensity: Increase 1012

  9. 1020 1 kHz OPA 1019 1018 250 kHz OPA 1017 1016 Ti: S 1015 1014 He-Ne 1013 1012 Time Resolved Photoluminescence Exciton Density 8.6 x 1017 cm-3 1.674eV 1.667eV EHP B BX A

  10. Time Resolved PhotoluminescenceExciton Density 8.6 x 1017 cm-3 1020 1 kHz OPA 1019 A 1018 250 kHz OPA 1017 1016 Ti: S 1015 Inverse Boltzman 1014 A: 1.674 eV t ~ 150 ps Biexciton B: 1.667 eV t < 30 ps ? He-Ne 1013 1012

  11. Many Body Effect of FEMPs Bi-polaron Bi-exciton Coupled two FEMPs has been expected to be more stable than single FEMP

  12. PhotoluminescenceExciton Density > Mott Density 1020 1 kHz OPA I = 5.6 × 1018 [cm-3] 1019 1018 250 kHz OPA 1017 1016 Ti: S 1015 1014 He-Ne 1013 Electron hole plasma  I4.2 Biexciton  I1.6 1012

  13. 1020 1 kHz OPA 1019 1018 250 kHz OPA 1017 1016 Ti: S 1015 1014 He-Ne 1013 1012 Exciton Density Dependence of Origin of Photoluminescence Electron hole Plasma FEMP Biexciton

  14. Summary PL measurements Exciton density: 1012 – 1020 [cm-3] FEMP  Biexciton Electron hole plasma Future work Spin Dynamics Under Strong Excitation

  15. Hole mass: Electron mass: Free Exciton Magnetic Polaron Mn spin Electron Hole 14.4Å 64Å The number of Mn ion electron: 481 hole: ~5.5

  16. Exciton Density Dependence Excitation intensity normalized FEMP PL int. 1020 FEMP binding energy 1 kHz OPA 1019 1018 250 kHz OPA 1017 1016 Ti: S 1015 1014 When the exciton density is above 1018 cm-3 FEMP may disappear He-Ne 1013 1012

  17. Spin Relaxation Dynamics 1020 1019 5K 1018 1017 1016 1015 1014 1013 1012

  18. 1020 1 kHz OPA 1019 1018 250 kHz OPA 1017 1016 Ti: S 1015 1014 He-Ne 1013 1012 Time Resolved Photoluminescence 1.4K 250 kHz OPA laser 76 MHz OPA laser

  19. Experimental Setup for PL measurements Sample 13 K 1kHz OPA&CPA chopper He-Ne Movable mirror Photodiode Lock-in Amplifier Spectro- meter

  20. Discussions

  21. Excitation Dependence of the PLIntensity Excited with Ti:Sapphire Laser

  22. Estimate by the EBX (4.1 meV) on CdSe

  23. Purpose

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