@article{oai:ynu.repo.nii.ac.jp:00009850,
 author = {Katayama, Ikufumi and Minami, Yasuo and Arashida, Yusuke and Handegard, Orjan Sele and Nagao, Tadaaki and Kitajima, Masahiro and Takeda, Jun},
 journal = {Proceedings of SPIE},
 month = {Sep},
 note = {By using both linear and nonlinear terahertz spectroscopy on epitaxial Bi and Bi_(1-x)Sb_x thin films, we systematically investigated the linear and nonlinear terahertz dynamics of Dirac electrons. The linear terahertz transmittance was analyzed by the Drude model up to 50 THz, and then the plasma frequency and the damping constant were evaluated as functions of the film thickness and Sb-concentration. We found surface metallic state for Bi ultra-thin films, while semimetal to semiconductor crossover for Bi_(1-x)Sb_x thin films. In the nonlinear terahertz spectroscopy, the terahertz transmittance increases with increasing the field strength, which could be assigned to the carrier acceleration along the Dirac-like band dispersion at the L point in the Brillouin zone. In addition, we observed the terahertz-induced absorption in terahertz-pump and terahertz-probe spectroscopy, which could be assigned to carrier generation due to Zener tunneling in Dirac band structure. The results demonstrate that Bi-related materials are promising candidates for future nonlinear terahertz devices., Copyright 2018 Society of Photo‑Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this publication for a fee or for commercial purposes, and modification of the contents of the publication are prohibited.},
 title = {Nonlinear terahertz dynamics of Dirac electrons in Bi thin films},
 volume = {10756},
 year = {2018}
}