中国物理B ›› 2014, Vol. 23 ›› Issue (4): 44206-044206.doi: 10.1088/1674-1056/23/4/044206

• ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS • 上一篇    下一篇

Gigahertz longitudinal acoustic phonons originating from ultrafast ligand field transitions in hematite thin films

徐悦a, 金钻明a b, 张郑兵a, 张泽宇a, 林贤a, 马国宏a, 程振祥c   

  1. a Laboratory of Ultrafast Photonics, Department of Physics, Shanghai University, Shanghai 200444, China;
    b Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany;
    c Institute for Superconductor and Electronic Materials, University of Wollongong, Squires Way, North Wollongong, NSW 2500, Australia
  • 收稿日期:2013-06-12 修回日期:2013-08-11 出版日期:2014-04-15 发布日期:2014-04-15
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No. 11174195).

Gigahertz longitudinal acoustic phonons originating from ultrafast ligand field transitions in hematite thin films

Xu Yue (徐悦)a, Jin Zuan-Ming (金钻明)a b, Zhang Zheng-Bing (张郑兵)a, Zhang Ze-Yu (张泽宇)a, Lin Xian (林贤)a, Ma Guo-Hong (马国宏)a, Cheng Zhen-Xiang (程振祥)c   

  1. a Laboratory of Ultrafast Photonics, Department of Physics, Shanghai University, Shanghai 200444, China;
    b Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany;
    c Institute for Superconductor and Electronic Materials, University of Wollongong, Squires Way, North Wollongong, NSW 2500, Australia
  • Received:2013-06-12 Revised:2013-08-11 Online:2014-04-15 Published:2014-04-15
  • Contact: Ma Guo-Hong, Cheng Zhen-Xiang E-mail:ghma@staff.shu.edu.cn;cheng@uow.edu.au
  • About author:42.50.Md; 78.20.hb; 78.47.J-
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No. 11174195).

摘要: The creation and propagation of longitudinal acoustic phonons (LAPs) in high quality hematite thin films (α-Fe2O3) epitaxially grown on different substrates (BaTiO3, SrTiO3, and LaAlO3) are investigated using the femtosecond pump-probe technique. Transient reflection measurements (ΔR/R) indicate the photo-excited electron dynamics, and the initial decay less than 1 ps and the slow decay of ~ 500 ps are attributed to the electron-LO phonon coupling and electron-hole nonradiative recombination, respectively. LAPs in α-Fe2O3 film can be created by ultrafast excitation of the ligand field state, such as the ligand field transitions under 800-nm excitation as well as the ligand to metal charge-transfer with 400-nm excitation. The strain modulations of the sound velocity and the out-of-plane elastic properties are demonstrated in α-Fe2O3 film on different substrates.

关键词: α-Fe2O3, pump-probe technique, acoustic phonons, ligand field

Abstract: The creation and propagation of longitudinal acoustic phonons (LAPs) in high quality hematite thin films (α-Fe2O3) epitaxially grown on different substrates (BaTiO3, SrTiO3, and LaAlO3) are investigated using the femtosecond pump-probe technique. Transient reflection measurements (ΔR/R) indicate the photo-excited electron dynamics, and the initial decay less than 1 ps and the slow decay of ~ 500 ps are attributed to the electron-LO phonon coupling and electron-hole nonradiative recombination, respectively. LAPs in α-Fe2O3 film can be created by ultrafast excitation of the ligand field state, such as the ligand field transitions under 800-nm excitation as well as the ligand to metal charge-transfer with 400-nm excitation. The strain modulations of the sound velocity and the out-of-plane elastic properties are demonstrated in α-Fe2O3 film on different substrates.

Key words: α-Fe2O3, pump-probe technique, acoustic phonons, ligand field

中图分类号:  (Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency)

  • 42.50.Md
78.20.hb (Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects) 78.47.J- (Ultrafast spectroscopy (<1 psec))