Abstract-Terahertz-field-induced carrier generation in B i 1 − x S b x Dirac electron systems

I. Katayama, H. Kawakami, T. Hagiwara, Y. Arashida, Y. Minami, L.-W. Nien, O. S. Handegard, T. Nagao, M. Kitajima, and J. Takeda

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.98.214302

Terahertz-field-induced carrier generation processes were investigated in Dirac electron systems, single-crystalline bismuth antimony alloy thin films ($B{i}_{1-x}S{b}_x$; $0\le x\le 0.16$). This investigation was performed by precisely tuning, via the substituent ratio $x$, the band structure of the films from that associated with a semimetal to that characteristic of a narrow-gap semiconductor. Terahertz-field-induced absorption was clearly observed within a few picoseconds after the terahertz pump-pulse illumination of $B{i}_{1-x}S{b}_x$ semimetal and semiconductor samples. The field-strength dependence of the induced absorption was compared with the calculated Zener tunneling probability in the Dirac-like band dispersion. Through this comparison, the mechanism of the induced absorption was attributed to the carrier generation via the terahertz-field-induced Zener tunneling. The tunneling occurred in subpicosecond timescales even at room temperature, demonstrating that $B{i}_{1-x}S{b}_x$ thin films are promising for future high-speed electronics and the investigation of universal ultrafast tunneling dynamics.

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