THz Generation and Detection on Dirac Fermions in Topological Insulators
Luo, C. W. · Lee, C. C. · Chen, H. -J. · Tu, C. M. · Ku, S. A. · Tzeng, W. Y. · Yeh, T. T. · Chiang, M. C. · Wang, H. J. · Chu, W. C. · Lin, J. -Y. · Wu, K. H. · Juang, J. Y. · Kobayashi, T. · Cheng, C. -M. · Chen, C. -H. · Tsuei, K. -D. · Berger, H. · Sankar, R. · Chou, F. C. · Yang, H. D.
Original · EN
This study shows that a terahertz (THz) wave can be generated from the (001) surface of cleaved Bi₂Se₃ and Cu-doped Bi₂Se₃ single crystals using 800 nm femtosecond pulses. The generated THz power is strongly dependent on the carrier concentration of the crystals. An examination of the dependence reveals the two-channel free carrier absorption to which Dirac fermions are indispensable. Dirac fermions in Bi₂Se₃ are significantly better absorbers of THz radiation than bulk carriers at room temperature. Moreover, the characteristics of THz emission confirm the existence of a recently proposed surface phonon branch that is normalized by Dirac fermions.
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